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| C | R | Score | PMID | Date | Au | Ab | Title | Journal |
|---|---|---|---|---|---|---|---|---|
| 6751 | 3.51 | 17957298 | 2008.01.23 | + | + | pH-Controllable drug release using hydrogel encapsulated mesoporous silica. | Chem Commun (Camb) | |
| SW Song, K Hidajat, S Kawi, | ||||||||
| Amine-functionalized mesoporous SBA-15 silica loaded with bovine serum albumin (BSA) has been successfully encapsulated with a thin layer coating of poly(acrylic acid) PAA, with the entrapped BSA being released from the PAA-encapsulated SBA-15 at the higher pH value of 7.4 rather than at the lower pH value of 1.2. This novel drug delivery system has a potential application in the release of protein drug to the site of higher pH value, such as small intestine or colon. | ||||||||
| 6752 | 3.51 | 16473444 | 2007.06.14 | + | + | Biomonitoring: is body burden relevant to public health? | Regul Toxicol Pharmacol | |
| D Paustenbach, D Galbraith, | ||||||||
| Biomonitoring is the study of the presence and concentration of chemicals in humans usually by the measurement of blood, urine or breath (exhaled air). Properly conducted, these data provide a picture of the amount of a chemical or agent actually absorbed into the body for a specific period of time. This review provides a history of biomonitoring, as well as the limitations and potential benefits of these studies. Examples of the proper and possibly improper use of biomonitoring and the impact made on our society are provided. Reasons for having comprehensive national biomonitoring programs are summarized, along with the societal benefits and risks. A brief discussion of the history of the NHANES program and select results from the 2005 Report are presented. By 2010, it has been predicted that the Centers for Disease Control (CDC) will be monitoring nearly 1000 chemicals in persons from all regions of the nation. The measurement of chemicals and biomarkers has revolutionized the field of exposure assessment. Overall, we recommend an approach of careful interpretation, understanding that the data obtained are useful for establishing baseline information about exposure, rather than equating detection with risk. We present suggestions for contextualizing biomonitoring results in order to provide the public with the tools to distinguish genuine health risks from trivial ones. | ||||||||
| 6753 | 3.51 | 16919859 | 2006.10.25 | + | + | Mouse aldo-keto reductase AKR7A5 protects V79 cells against 4-hydroxynonenal-induced apoptosis. | Toxicology | |
| D Li, A Hinshelwood, R Gardner, G McGarvie, EM Ellis, | ||||||||
| We have developed transgenic Chinese hamster V79 cell lines in order to examine the potential for a mouse aldo-keto reductase, AKR7A5, to protect against the toxicity of 4-hydroxynonenal (4-HNE) and related toxic aldehydes. Stable expression of mouse AKR7A5 in V79 cells conferred four-fold increased resistance to 4-HNE cytotoxicity using the MTT assay compared to empty vector-transfected V79 cells. Cells expressing AKR7A5 showed a decrease in mutation rate compared to control cells in the presence of 4-HNE as measured by HGPRT mutagenicity assay. Furthermore, the cells expressing AKR7A5 showed decreased 4-HNE-induced caspase-3 activity in both a time and dose-dependent manner compared to control cells. These results show that in V79 cells 4-HNE mediates apoptosis via caspase-3 activation and that the AKR7A5 enzyme is able to metabolize 4-HNE in cells, thereby attenuating 4-HNE-induced apoptosis. AKR7A isozymes may therefore be important in protecting against toxic aldehydes derived from lipid peroxidation in vivo. | ||||||||
| 6754 | 3.50 | 15296230 | 2004.09.08 | + | + | Self-organization of carbide superlattice and nucleation of carbon nanotubes. | J Nanosci Nanotechnol | |
| F Tsui, PA Ryan, | ||||||||
| In metal-carbon systems with known stable compounds, carbide nanocrystals self-organize epitaxially on metal surfaces to form two-dimensional arrays during carbon deposition. The process is energetically driven by the competition between the strain and surface energies, and it appears to play an important role in the nucleation of single-walled carbon nanotubes. Interplay between energetics and kinetics controls carbon precipitation from the superlattice, such that the length scale of the carbide and superlattice appears to control the size and morphology of the precipitates. Furthermore, carbon precipitates appear to be "seedlings" of carbon nanotubes grown on top of the carbide nanocrystals. These findings reveal that the nucleation of carbon nanotubes is a nonequilibrium process and that a stable carbide superlattice can be used as an ordered template of carbon saturated "roots" for nucleating nanotube bundles with controlled diameter, spacing, and perhaps chirality. | ||||||||
| 6755 | 3.50 | 18590460 | 2008.11.17 | + | + | Photosensitiser delivery for photodynamic therapy. Part 1: Topical carrier platforms. | Expert Opin Drug Deliv | |
| RF Donnelly, PA McCarron, DI Morrow, SA Sibani, AD Woolfson, | ||||||||
| BACKGROUND: Photodynamic therapy (PDT) is a medical treatment in which a combination of a photosensitising drug and visible light causes destruction of selected cells. Due to the lack of true selectivity of preformed photosensitisers for neoplastic tissue and their high molecular weights, PDT of superficial skin lesions has traditionally been mediated by topical application of the porphyrin precursor 5-aminolevulinic acid (ALA). OBJECTIVE: This article aims to review the traditional formulation-based approaches taken to topical delivery of ALA and discusses the more innovative strategies investigated for enhancement of PDT mediated by topical application of ALA and preformed photosensitisers. METHODS: All of the available published print and online literature in this area was reviewed. As drug delivery of agents used in PDT is still something of an emerging field, it was not necessary to go beyond literature from the last 30 years. RESULTS/CONCLUSION: PDT of neoplastic skin lesions is currently based almost exclusively on topical application of simple semisolid dosage forms containing ALA or its methyl ester. Until expiry of patents on the current market-leading products, there is unlikely to be a great incentive to engage in design and evaluation of innovative formulations for topical PDT, especially those containing the more difficult-to-deliver preformed photosensitisers. | ||||||||
| 6756 | 3.50 | 17560995 | 2007.10.19 | + | + | Multiple mechanisms underlying the anticancer action of nanocrystalline fullerene. | Eur J Pharmacol | |
| L Harhaji, A Isakovic, N Raicevic, Z Markovic, B Todorovic-Markovic, N Nikolic, S Vranjes-Djuric, I Markovic, V Trajkovic, | ||||||||
| Using the rat glioma cell line C6 and the human glioma cell line U251, we demonstrate the multiple mechanisms underlying the in vitro anticancer effects of the C(60) fullerene water suspension (nano-C(60) or nC(60)) produced by solvent exchange method. Nano-C(60) in a dose-dependent manner reduced the tumor cell numbers after 24 h of incubation. The observed antiglioma action of nC(60) at high concentration (1 microg/ml) was due to a reactive oxygen species-mediated necrotic cell damage that was partly dependent on oxidative stress-induced activation of extracellular signal-regulated kinase (ERK). On the other hand, low-dose nC(60) (0.25 microg/ml) did not induce either necrotic or apoptotic cell death, but caused oxidative stress/ERK-independent cell cycle block in G(2)/M phase and subsequent inhibition of tumor cell proliferation. Treatment with either high-dose or low-dose nC(60) caused the appearance of acidified intracytoplasmic vesicles indicative of autophagy, but only the antiglioma effect of low-dose nC(60) was significantly attenuated by inhibiting autophagy with bafilomycin A1. Importantly, primary rat astrocytes were less sensitive than their transformed counterparts to a cytostatic action of low-dose nC(60). These data provide grounds for further development of nC(60) as an anticancer agent. | ||||||||
| 6757 | 3.50 | 12908423 | 2003.09.29 | + | + | DNA-directed magnetic network formations with ferromagnetic nanoparticles. | J Nanosci Nanotechnol | |
| HY Lee, Y Sacho, T Kanki, H Tanaka, H Shirakawa, JW Cheon, JH Yoon, NJ Kang, JI Park, T Kawai, | ||||||||
| We formed a DNA network embedding ferromagnetic cobalt nanoparticles with a 12-nm diameter through a nanoscale self-assembly of DNA molecules on large-scale mica surfaces (12 mm x 12 mm); we then confirmed its structural characteristics with an atomic force microscope. Moreover, noncontact magnetic force microscope measurement revealed that some embedded cobalt nanoparticles have different directions of magnetization, similar to "bits" in magnetic data storage devices. | ||||||||
| 6758 | 3.50 | 16792382 | 2006.07.27 | + | + | Alignment of glycolipid nanotubes on a planar glass substrate using a two-step microextrusion technique. | J Nanosci Nanotechnol | |
| Y Guo, H Yui, A Fukagawa, S Kamiya, M Masuda, K Ito, T Shimizu, | ||||||||
| We have developed a two-step microextrusion technique to align lipid nanotubes of 200 nm in diameter in parallel on planar glass substrates. This technique is useful to align self-assembled molecular nanofibers or nanotubes with diameters ranging from 100 to 300 nm. In the first step, we applied relatively large air pressure (approximately 40 hPa) onto a microcapillary filled with aqueous dispersion of lipid nanotubes to push them out. An aqueous droplet with 60 microm diameter was then extruded from the tip of the microcapillary. After one end of the lipid nanotube moved out, we changed the air pressure to be smaller, approximately 20 hPa to reduce the flow rate of the dispersion. The decrease in size of the droplet allowed us to fix the exposed end of the lipid nanotube onto the planar substrate. By dragging the microcapillary along the planar surface, we were able to align the whole nanotube onto the substrate. Using this technique, we have achieved the parallel alignment of the lipid nanotubes on the glass substrate. | ||||||||
| 6759 | 3.50 | 15848253 | 2005.07.28 | + | + | Silver accumulation in Daphnia magna in the presence of reactive sulfide. | Aquat Toxicol | |
| A Bianchini, C Rouleau, CM Wood, | ||||||||
| Previously, we demonstrated a higher silver body burden when Daphnia magna were exposed to silver in the presence of environmentally relevant concentrations (25 nM) of reactive sulfide, but the explanation was unclear. In the present study, D. magna were exposed to AgNO3 (0.93 microg Ag/L=8.6 nM as a mixture of cold Ag and (110m)Ag) in synthetic water in either the presence or absence of 25 nM sulfide as zinc sulfide clusters. After 1-h exposure, daphnids were transferred to clean water for up to 5-h depuration. At different times of Ag exposure and depuration, daphnids were randomly sampled for whole body silver burden. Also, after 1 h, daphnids were sampled for silver accumulation in "gills" (small organs on the thoracic appendages), digestive tract, and carcass. Other groups were exposed to the same silver and sulfide concentrations for 1 h and then sampled for whole-body autoradiography. Silver body burden was about two-fold higher in the presence of sulfide. A two-fold increase in silver burden in "gills" and digestive tract, but not in carcass, was also observed in the presence of sulfide. Absolute differences due to sulfide were greatest in digestive tract and explained most of the difference in whole body burden. Transfer to clean water caused a significant drop in silver concentration in whole body and all compartments to similar levels in the two groups after 5-h depuration. These results indicate that the higher silver body burden observed in the presence of sulfide is mainly due to sulfide-bound silver in the digestive tract of the daphnids. This conclusion is supported by autoradiography, which showed a high concentration of silver in the digestive tract of daphnids exposed to Ag/sulfide. | ||||||||
| 6760 | 3.50 | 15588903 | 2005.04.21 | + | + | Controlled release of proteins from degradable poly(ether-ester) multiblock copolymers. | J Control Release | |
| R van Dijkhuizen-Radersma, S Métairie, JR Roosma, K de Groot, JM Bezemer, | ||||||||
| A new series of multiblock poly(ether-ester)s based on poly(ethylene glycol) (PEG), butylene terephthalate (BT) and butylene succinate (BS) segments were introduced as matrices for controlled release applications. The release of two model proteins, lysozyme and bovine serum albumin (BSA), from poly(ether-ester) films were evaluated and correlated to the swelling and degradation characteristics of the polymer matrices. First- and zero-order profiles were found for the release of lysozyme, depending on the composition of the polymer matrix. The initial diffusion coefficient was correlated to the swelling of the matrix, which increased with longer PEG segments and lower BT/BS ratios of the polymer. High swelling matrices released the lysozyme according to diffusion-controlled first-order release profiles. Zero-order release profiles were obtained from less swollen matrices due to a combination of diffusion and degradation of the matrix. In contrast to the release of lysozyme, BSA was released from the poly(ether-ester) matrices via delayed release profiles. Both the delay time and the release rate could be tailored by varying the matrix composition. The BSA release rate was mainly determined by the degradation, whereas the delay time was determined by a combination of the swelling and the degradation rate of the polymer matrix. | ||||||||
| 6761 | 3.50 | 16112780 | 2006.07.31 | + | + | Records of atmospheric delivery of pyrolysis-derived pollutants in recent mountain lake sediments of the Julian Alps (NW Slovenia). | Environ Pollut | |
| G Muri, SG Wakeham, NL Rose, | ||||||||
| The historical record of the input of pyrolysis-derived pollutants via the atmosphere, i.e. black carbon (BC), polycyclic aromatic hydrocarbons (PAH) and spheroidal carbonaceous particles (SCP) was measured in the sediments of three remote alpine lakes situated in the Julian Alps, northwest Slovenia. Parallel sedimentary trends for BC, PAH and SCP were observed across the Julian Alps and relationships among these contaminants are discussed. Inputs of these pyrolytic-contaminants to sediments of remote lakes started to rise at the end of the 19th century, while their peak inputs were observed in the mid-20th century, amounting up to 6.0 gm(-2) yr(-1) for BC, 5200 x 10(4) m(-2) yr(-1) for SCP and 2900 microg m(-2) yr(-1) for PAH. In the last two to three decades, inputs decreased substantially, by a factor of up to 3 for BC, 7 for SCP and at least 3 for PAH. | ||||||||
| 6762 | 3.50 | 17997187 | 2008.05.19 | + | + | Biomaterials for stem cell differentiation. | Adv Drug Deliv Rev | |
| E Dawson, G Mapili, K Erickson, S Taqvi, K Roy, | ||||||||
| The promise of cellular therapy lies in the repair of damaged organs and tissues in vivo as well as generating tissue constructs in vitro for subsequent transplantation. Unfortunately, the lack of available donor cell sources limits its ultimate clinical applicability. Stem cells are a natural choice for cell therapy due to their pluripotent nature and self-renewal capacity. Creating reserves of undifferentiated stem cells and subsequently driving their differentiation to a lineage of choice in an efficient and scalable manner is critical for the ultimate clinical success of cellular therapeutics. In recent years, a variety of biomaterials have been incorporated in stem cell cultures, primarily to provide a conducive microenvironment for their growth and differentiation and to ultimately mimic the stem cell niche. In this review, we examine applications of natural and synthetic materials, their modifications as well as various culture conditions for maintenance and lineage-specific differentiation of embryonic and adult stem cells. | ||||||||
| 6763 | 3.49 | 17697763 | 2008.02.15 | + | + | Effects of trichlorfon on malondialdehyde and antioxidant system in human erythrocytes. | Toxicol In Vitro | |
| B Karademir Catalgol, S Ozden, B Alpertunga, | ||||||||
| Organophosphorus insecticides may induce oxidative stress leading to generation of free radicals and alteration in antioxidant system. The aim of this study was to examine the potency of trichlorfon, an organophosphate insecticide, to induce oxidative stress response in human erythrocytes in vitro. For this purpose trichlorfon solutions in different concentrations and erythrocyte solutions were incubated at 37 degrees C for 60 min. At the end of the incubation time, malondialdehyde (MDA), an end product of lipid peroxidation, total glutathione, reduced glutathione (GSH) levels, activities of superoxide dismutase (SOD), catalase (CAT), glutathione peroxidase (GSH-Px) enzymes were determined by spectrophotometric methods. Trichlorfon increased MDA formation depended on the concentration. On the other hand, decreases in the GSH-Px activity, GSH levels and increases in the total glutathione levels, SOD and CAT activities were seen in the studied concentrations. The present findings indicate that the in vitro toxicity of trichlorfon may be associated with oxidative stress. | ||||||||
| 6764 | 3.49 | 15081272 | 2004.05.19 | + | + | Effect of nickel and iron co-exposure on human lung cells. | Toxicol Appl Pharmacol | |
| K Salnikow, X Li, M Lippmann, | ||||||||
| Exposure to ambient air particulate matter (PM) is associated with increased mortality and morbidity in susceptible populations. The epidemiological data also suggest a relationship between PM air pollution and impairment of cardiopulmonary function. The mechanisms that may be responsible for these effects are not fully understood and are likely related to perturbations of cellular and molecular functions. One type of PM, residual oil fly ash (ROFA), is of particular interest. ROFA does not contain much organic material, but does contain relatively high quantities of transition metals, predominantly nickel, vanadium, and iron, as well as black carbon and sulfates. In this study, we investigated the effect of two metals (iron and nickel) on the induction of "hypoxia-like" stress and the production of interleukins (ILs) in minimally transformed human airway epithelial cells (1HAEo(-)). We found that exposure to soluble nickel sulfate results in the induction of hypoxia-inducible genes and IL-8 production by the 1HAEo(-) cells. The simultaneous addition of iron in either ferric or ferrous form and nickel completely inhibited IL-8 production and had no effect on "hypoxia-like" stress caused by nickel, suggesting the existence of two different pathways for the induction "hypoxia-like" stress and IL-8 production. The effect of nickel was not related to the blocking of iron entry into cells since the level of intracellular iron was not affected by co-exposure with nickel. The obtained data indicate that nickel can induce different signaling pathways with or without interference with iron metabolism. Our observations suggest that in some cases the excess of iron in PM can cancel the effects of nickel. | ||||||||
| 6765 | 3.49 | 16053929 | 2005.09.09 | + | + | Brain thiobarbituric acid-reactive substances in rats after short periods of ozone exposure. | Environ Res | |
| C Escalante-Membrillo, A Gonzalez-Maciel, R Reynoso-Robles, R Gonzalez-Pina, | ||||||||
| It has been proposed that molecules derived from reactions that occur between the ozone and the lung tissue mediate nonpulmonary effects caused by ozone exposure. Free radicals are among those proposed molecules that flow throughout the bloodstream to other organs producing lipid peroxidation. In order to elucidate on aspect of ozone toxicity mechanisms, we measured the thiobarbituric acid-reactive products (TBARS), as an index of lipid peroxidation, in a variety of brain regions in rats exposed to 1 ppm of ozone for 1, 3, 6, and 9h. Another group exposed to 9h of O(3) plus 3h of clean-air exposure was also included. The results showed an important increase in TBARS content in all the studied structures. Such effect seems to be transient. These findings indicates that acute ozone exposure can produce cerebral peroxidation as it has been found in rats exposed chronically, suggesting an involvement of free radicals in brain effects of ozone exposure. | ||||||||
| 6766 | 3.49 | 17100746 | 2007.01.17 | + | + | Inflammatory response to a titanium surface with potential bioactive properties: an in vitro study. | Clin Implant Dent Relat Res | |
| A Göransson, C Gretzer, A Johansson, YT Sul, A Wennerberg, | ||||||||
| BACKGROUND: The current hard tissue implants research aims to accelerate bone healing by designing surfaces that are bioactive. However, the role of the inflammatory response to these surfaces is so far incompletely described. PURPOSE: The aim of the study was to evaluate early inflammatory response in vitro to a potentially bioactive surface--an anodized surface with Mg ions incorporated (anodized/Mg)--and to compare it to a turned, a blasted, and an anodized surface. MATERIALS AND METHODS: An interferometer was used for topographical characterizations. The disks were incubated with human mononuclear cells. Adherent cells were investigated with respect to number of cells, viability, differentiation, and cytokine production with and without lipopolysaccharide stimulation after 24 and 72 hours. RESULTS: The number of adhered mononuclear cells differed significantly between the different modified surfaces, with the highest number on the anodized surface. However, there were no significant differences in cytokine production and differentiation between the different modified surfaces. The amount of anti-inflammatory mediator interleukin-10 remained over time, while the number of cells and pro-inflammatory cytokine tumor necrosis factor-alpha decreased. The cells were viable on all surfaces, respectively. CONCLUSION: The anodized surfaces with and without Mg ions showed an increased cell adherence, however, otherwise an inflammatory response similar to the turned and blasted surfaces. Furthermore, the potentially bioactive anodized/Mg surface showed a similar response to the TiUnite-like anodized surface despite the former having a surface roughness of a smoother character. | ||||||||
| 6767 | 3.49 | 17886062 | 2007.11.19 | + | + | Environmental polycyclic aromatic hydrocarbons (PAHs) enhance allergic inflammation by acting on human basophils. | Inhal Toxicol | |
| W Schober, S Lubitz, B Belloni, G Gebauer, J Lintelmann, G Matuschek, I Weichenmeier, B Eberlein-König, J Buters, H Behrendt, | ||||||||
| Diesel exhaust particles (DEPs) have been implicated in the worldwide increased incidence of allergic airway diseases over the past century. There is growing evidence that DEP-associated polycyclic aromatic hydrocarbons (PAHs) participate in the development and maintenance of immunoglobulin (Ig) E-mediated allergic diseases. To address this issue we investigated the impact of U.S. Environmental Protection Agency (EPA) priority PAHs as well as of PAH-containing airborne extracts on antigen-induced CD63 upregulation and mediator release from human basophils. Whole blood samples from birch pollen allergic and control subjects were incubated in the presence of organic extracts of urban aerosol (AERex) or EPA-PAH standard with or without rBet v 1. Basophils were analyzed for CD63 expression as a measure of basophil activation by using multiparameter flow cytometry. In addition, purified basophils from birch pollen allergic donors were incubated for 2 h in the presence of 1 muM benzo[a]pyrene (BaP) or phenanthrene (Phe) and then stimulated with rBet v 1 for 45 min. Supernatants were assayed for histamine, interleukin (IL)-4, and IL-8 by means of enzyme-linked immunosorbent assay (ELISA). Basophils exposed in vitro simultaneously to AERex or EPA-PAH standard and rBet v 1 expressed CD63 significantly more than with antigen alone. PAHs synergized with rBet v 1 dose dependently, but did not activate basophils from nonallergic donors. BaP and Phe significantly enhanced cytokine secretion (IL-4, IL-8) and histamine release from purified basophils without antigen added, and secretion was not further enhanced by rBet v 1 stimulation. In conclusion, PAHs from roadside emissions can directly activate sensitized basophils to cytokine secretion and drive proallergic processes through enhanced Fcepsilon RI-coupled mediator release from human basophils. | ||||||||
| 6768 | 3.49 | 17616164 | 2007.10.19 | + | + | Computational design of an RNA hexagonal nanoring and an RNA nanotube. | Nano Lett | |
| YG Yingling, BA Shapiro, | ||||||||
| The combination of computer modeling, RNA structure versatility, and siRNA function can be efficiently used to design an all-RNA nanoparticle capable of siRNA delivery. Here, we present a computational design of an RNA nanoring and a nanotube. An RNA nanoring consists of six simple linear building blocks that are assembled together via known noncovalent loop-loop contacts based on RNAI/RNAII inverse sequences. The helical sequences of the building blocks can include siRNAs for drug delivery. | ||||||||
| 6769 | 3.49 | 16458199 | 2006.05.02 | + | + | Nitric oxide protects the mitochondria of anterior pituitary cells and prevents cadmium-induced cell death by reducing oxidative stress. | Free Radic Biol Med | |
| AH Poliandri, LI Machiavelli, AF Quinteros, JP Cabilla, BH Duvilanski, | ||||||||
| Cadmium (Cd2+) is a highly toxic metal that affects the endocrine system. We have previously shown that Cd2+ induces caspase-3 activation and apoptosis of anterior pituitary cells and that endogenous nitric oxide (NO) protects these cells from Cd2+. Here we investigate the mechanisms by which NO exerts this protective role. Cd2+ (25 microM) reduced the mitochondrial membrane potential (MMP) as measured by flow cytometry. Cd2+-induced apoptosis was mitochondrial dependent since cyclosporin A protected the cells from this metal. Inhibition of NO synthesis with 0.5 mM L-NAME increased the effect of Cd2+ on MMP, whereas the NO donor DETANONOate (0.1 mM) reduced it. Cd2+ increased the production of reactive oxygen species (ROS) as measured by flow cytometry. This effect was electron-transfer-chain-dependent since it was inhibited by rotenone. In fact, rotenone reduced the cytotoxic effect of the metal. The action of Cd2+ on mitochondrial integrity was ROS dependent. Trolox, an antioxidant, inhibited the effect of the metal on the MMP. Cd2+-induced increase in ROS generation was reduced by DETANONOate. There are discrepancies concerning the role of NO in Cd2+ toxicity. Here we show that NO reduces Cd2+ toxicity by protecting the mitochondria from oxidative stress in a system where NO plays a regulatory role. | ||||||||
| 6770 | 3.49 | 12751635 | 2004.02.26 | + | + | Large porous particle impingement on lung epithelial cell monolayers--toward improved particle characterization in the lung. | Pharm Res | |
| J Fiegel, C Ehrhardt, UF Schaefer, CM Lehr, J Hanes, | ||||||||
| PURPOSE: The ability to optimize new formulations for pulmonary delivery has been limited by inadequate in vitro models used to mimic conditions particles encounter in the lungs. The aim is to develop a physiologically-relevant model of the pulmonary epithelial barrier that would allow for quantitative characterization of therapeutic aerosols in vitro. METHODS: Calu-3 human bronchial epithelial cells were cultured on permeable filter inserts under air-interfaced culture (AIC) and liquid-covered culture (LCC) conditions. Calu-3 cells grown under both conditions formed tight monolayers and appeared physiologically similar by SEM and immunocytochemical staining against cell junctional proteins and prosurfactant protein-C. RESULTS: Aerosolized large porous particles (LPP) deposited homogeneously and reproducibly on the cell surface and caused no apparent damage to cell monolayers by SEM and light microscopy. However, monolayers initially grown under LCC conditions showed a significant decrease in barrier properties within the first 90 min after impingement with microparticles, as determined by transepithelial electrical resistance (TEER) measurements and fluorescein-sodium transport. Conversely, AIC grown monolayers showed no significant change in barrier properties within the first 90 min following particle application. A dense mucus coating was found on AIC grown Calu-3 monolayers, but not on LCC grown monolayers, which may protect the cell surface during particle impinging. CONCLUSION: This in vitro model, based on AIC grown Calu-3 cells, should allow a more relevant and quantitative characterization of therapeutic aerosol particles intended for delivery to the tracheobronchial region of the lung or to the nasal passages. Such characterization is likely to be particularly important with therapeutic aerosol particles designed to provide sustained drug release in the lung. | ||||||||
| 6771 | 3.49 | 14552772 | 2004.06.16 | + | + | QSAR study on antibacterial activity of sulphonamides and derived Mannich bases. | Bioorg Med Chem Lett | |
| S Joshi, N Khosla, | ||||||||
| The paper describes synthesis and comparative study on antibacterial activities of sulphonamides and Mannich bases derived from them. The compounds were screened for their antibacterial activity against various gram-positive and gram-negative bacteria and were analyzed statistically. The results have shown that the compounds are quiet active against pathogens under study and were nontoxic. | ||||||||
| 6772 | 3.48 | 18572570 | 2008.07.22 | + | + | Melt mixed composites of poly(ethylene-co-methacrylic acid) ionomers and multiwall carbon nanotubes: influence of specific interactions. | J Nanosci Nanotechnol | |
| S Bose, AR Bhattacharyya, M Chawley, PV Kodgire, AR Kulkarni, A Misra, P Pötschke, | ||||||||
| Multiwall carbon nanotubes (MWNT) were melt-mixed with poly(ethylene-co-methacrylic acid) ionomers (Surlyn) using twin screw microcompounder. The specific interactions existing between the Na+ moieties in Surlyn and the pi electron clouds of MWNT were supported by FTIR and Raman spectroscopic analysis. SAXS scattering patterns were found to be progressively broadened in presence of MWNT in Surlyn/MWNT composites. Morphological investigations revealed selective clustering of MWNT in the vicinity of the ionic domains in Surlyn. Further, the domain size of the ionic clusters was found to increase with increasing MWNT content disrupting the ionic pairs apart in the ionic domain. The melt rheological response of Surlyn was significantly affected in presence of MWNT and was profoundly dependent on the ionic clusters. The state of dispersion of MWNT was assessed by AC electrical conductivity measurements. The associated percolation threshold was observed between 1.5-2 wt% of MWNT. | ||||||||
| 6773 | 3.48 | 8842041 | 1997.06.12 | + | + | Effect of size and serum proteins on transfection efficiency of poly ((2-dimethylamino)ethyl methacrylate)-plasmid nanoparticles. | Pharm Res | |
| JY Cherng, P van de Wetering, H Talsma, DJ Crommelin, WE Hennink, | ||||||||
| PURPOSE: The aim of this study was to gain insight into the relation between the physical characteristics of particles formed by a plasmid and a synthetic cationic polymer (poly(2-dimethylamino)ethyl methacrylate, PDMAEMA) and their transfection efficiency. METHODS: The PDMAEMA-plasmid particles were characterized by dynamic light scattering (size) and electrophoretic mobility measurements (charge). The transfection efficiency was evaluated in cell culture (COS-7 cells) using a pCMV-lacZ plasmid coding for beta-galactosidase as a reporter gene. RESULTS: It was shown that the optimal transfection efficiency was found at a PDMAEMA-plasmid ratio of 3 (w/w), yielding stable and rather homogeneous particles (diameter 0.15 micron) with a narrow size distribution and a slightly positive charge. Particles prepared at lower weight ratios, showed a reduced transfection efficiency and were unstable in time as demonstrated by DLS measurements. Like other cationic polymers, PDMAEMA is slightly cytotoxic. This activity was partially masked by complexing the polymer with DNA. Interestingly, the transfection efficiency of the particles was not affected by the presence of serum proteins. CONCLUSIONS: PDMAEMA is an interesting vector for the design of in vivo and ex vivo gene transfection systems. | ||||||||
| 6774 | 3.48 | 12627643 | 2003.04.17 | + | + | Copper bioaccumulation by the freshwater snail Lymnaea peregra: a toxicological marker of environmental and human health? | Environ Toxicol Chem | |
| FB Pyatt, MR Metcalfe, AJ Pyatt, | ||||||||
| Snails (Lymnaea peregra) were exposed to both low and high concentrations of copper(as copper nitrate) undercontrolled conditions and then were sacrificed and dissected; various tissues/organs were removed and subsequently analyzed by atomic absorption spectrophotometry to determine both the copper concentration and the nature of localization. At low concentrations, bioaccumulation was evident in various tissues/organs; a dose response occurred in tissues derived from both the head and foot. At high concentrations, the copper concentrations of the liver-like body and kidney became massively enhanced. There was some variability in the ranking of tissues/organs with regard to copper bioaccumulation--this was predominantly linked to the copper concentration to which the snails were exposed. Mechanisms of copper bioaccumulation are reviewed and comparisons with other organisms made. | ||||||||
| 6775 | 3.48 | 8020448 | 1994.08.04 | + | + | Review of the carcinogenic potential of gasoline. | Environ Health Perspect | |
| GK Raabe, | ||||||||
| This review examines the animal, human, and mechanistic studies that precede the new studies reported in this volume. Wholly vaporized unleaded gasoline was found to produce a dose-dependent increase in renal carcinoma in male rats and an excess above background incidence of hepatocellular tumors in female mice in the high-dose group. Mechanistic studies suggest that gasoline is not mutagenic and that the probable mechanism for the male rat renal tumors involves a rat-specific protein, alpha 2u-globulin, whose binding with highly branched aliphatic compounds results in renal tubule cell death and, in turn, a proliferative sequence that increases renal tubule tumors. Human evidence generated predominantly from studies of refinery workers does not support a kidney or liver cancer risk in humans. The current epidemiologic database is inadequate to access leukemia risk from low-level benzene exposure from gasoline. Studies of gasoline-exposed workers that incorporate quantitative exposure information are needed. | ||||||||
| 6776 | 3.48 | 16471518 | 2006.08.21 | + | + | Synthesis and structure characterization of chromium oxide prepared by solid thermal decomposition reaction. | J Phys Chem B | |
| L Li, ZF Yan, GQ Lu, ZH Zhu, | ||||||||
| Mesoporous chromium oxide (Cr2O3) nanocrystals were first synthesized by the thermal decomposition reaction of Cr(NO3)3.9H2O using citric acid monohydrate (CA) as the mesoporous template agent. The texture and chemistry of chromium oxide nanocrystals were characterized by N2 adsorption-desorption isotherms, FTIR, X-ray diffraction (XRD), UV-vis, and thermoanalytical methods. It was shown that the hydrate water and CA are the crucial factors in influencing the formation of mesoporous Cr2O3 nanocrystals in the mixture system. The decomposition of CA results in the formation of a mesoporous structure with wormlike pores. The hydrate water of the mixture provides surface hydroxyls that act as binders, making the nanocrystals aggregate. The pore structures and phases of chromium oxide are affected by the ratio of precursor-to-CA, thermal temperature, and time. | ||||||||
| 6777 | 3.48 | 15769534 | 2005.07.27 | + | + | The fibroblast response to tubes exhibiting internal nanotopography. | Biomaterials | |
| CC Berry, MJ Dalby, D McCloy, S Affrossman, | ||||||||
| The use of three-dimensional scaffolds in cell and tissue engineering is widespread; however, the use of such scaffolds, which bear additional cellular cues such as nanotopography, is as yet in its infancy. This paper details the novel fabrication of nylon tubes bearing nanotopography via polymer demixing, and reports that the topography greatly influenced fibroblast adhesion, spreading, morphology and cytoskeletal organisation. The use of such frameworks that convey both the correct mechanical support for tissue formation and stimulate cells through topographical cues may pave the way for future production of intelligent materials and scaffolds. | ||||||||
| 6778 | 3.47 | 18359523 | 2008.10.02 | + | + | Effect of dissolved organic matter source on phytotoxicity to Lemna aequinoctialis. | Aquat Toxicol | |
| R Shoji, | ||||||||
| The effect of dissolved organic matter (DOM) on metal toxicity to aquatic organisms has been reported. Biotic ligand model (BLM) can account for this factor to predict metal toxicity. However, few attempts have been made to assess the effect of the DOM on metal phytotoxicity to duckweeds. The objectives of this study were to examine the effect of DOM on copper toxicity to the duckweed Lemna aequinoctialis, and to determine if DOM concentration alone, regardless of DOM source, is an acceptable input parameter for the BLM for copper. Nine different DOM isolates from nine different sites in Japan were used in this study. A significant difference was observed between the lowest and the highest copper binding capacity. Phytotoxicity for copper decreased with increasing DOM concentration. These observations support use of the copper biotic ligand model (BLM) with AFA% (active fulvic acid percent) as a regulatory tool to predict copper phytotoxicity on duckweeds. | ||||||||
| 6779 | 3.47 | 11922461 | 2002.09.30 | + | + | Surface modification of superparamagnetic magnetite nanoparticles and their intracellular uptake. | Biomaterials | |
| Y Zhang, N Kohler, M Zhang, | ||||||||
| Superparamagnetic magnetite nanoparticles were surface-modified with poly (ethylene glycol) (PEG) and folic acid, respectively, to improve their intracellular uptake and ability to target specific cells. PEG and folic acid were successfully immobilized on the surfaces of magnetite nanoparticles and characterized using fourier transform infrared spectra. The nanoparticle internalization into mouse macrophage (RAW 264.7) and human breast cancer (BT20) cells was visualized using both fluorescence and confocal microscopy, and quantified by inductively coupled plasma emission spectroscopy (ICP). After the cells were cultured for 48 h in the medium containing the nanoparticles modified with PEG or folic acid, the results of fluorescence and confocal microscopy showed that the nanoparticles were internalized into the cells. The ICP measurements indicated that the uptake amount of PEG-modified nanoparticles into macrophage cells was much lower than that of unmodified nanoparticles. while folic acid modification did not change the amount of the uptake. However, for breast cancer cells, both PEG and folic acid modification facilitated the nanoparticle internalization into the cells. Therefore, PEG and folic acid modification of magnetite nanoparticles could be used to resist the protein adsorption and thus avoid the particle recognition by macrophage cells, and to facilitate the nanoparticle uptake to specific cancer cells for cancer therapy and diagnosis. | ||||||||
| 6780 | 3.47 | 18205056 | 2008.04.09 | + | + | Detoxification of phenol through bound residue formation by birnessite in soil: transformation kinetics and toxicity. | J Environ Sci Health A Tox Hazard Subst Environ Eng | |
| JW Jung, S Lee, H Ryu, KH Kang, K Nam, | ||||||||
| Oxidative coupling reaction of phenol mediated by birnessite was studied in aqueous phase and soil. Phenol was readily transformed by birnessite and almost all phenol disappeared in both samples after 24 hours of reaction. Phenol transformation kinetics was investigated by plotting reaction time against logarithm concentrations of residual phenol, revealing that exponential decrease of phenol was evident both in aqueous phase and soil, and maximum removal rates were 2.31-2.54 times higher in the presence of soil. Reaction products of phenol were identified by LC-MS and capillary electrophoresis. In aqueous phase, polyphenols were formed by self-coupling reaction of phenoxy radicals whereas phenol was found to be present as bound residues in soil, probably due to the cross-coupling reaction between the radicals and soil organic matter. Microtox System was employed to determine the toxicity after birnessite treatment, and the toxicity of phenol-spiked solution and soil samples decreased remarkably compared to that of phenol solution before treatment. | ||||||||
| 6781 | 3.47 | 16000220 | 2005.10.27 | + | + | Three-dimensional growth of differentiating MC3T3-E1 pre-osteoblasts on porous titanium scaffolds. | Biomaterials | |
| JP St-Pierre, M Gauthier, LP Lefebvre, M Tabrizian, | ||||||||
| The present work assesses the potential of three-dimensional porous titanium scaffolds produced by a novel powder metallurgy process for applications in bone engineering through in vitro experimentation. Mouse MC3T3-E1 pre-osteoblasts were used to investigate the proliferation (DNA content), differentiation (alkaline phosphatase activity and osteocalcin release) and mineralisation (calcium content) processes of cells on titanium scaffolds with average pore sizes ranging from 336 to 557 microm, using mirror-polished titanium as reference material. Scanning electron microscopy was employed to qualitatively corroborate the results. Cells proliferate on all materials before reaching a plateau at day 9, with proliferation rates being significantly higher on foams (ranging from 123 to 163 percent per day) than on the reference material (80% per day). Alkaline phosphatase activity is also significantly elevated on porous scaffolds following the proliferation stage. However, cells on polished titanium exhibit greater osteocalcin release toward the end of the differentiation process, resulting in earlier mineralisation of the extracellular matrix. Nevertheless, the calcium content is similar on all materials at the end of the experimental period. Average pore size of the porous structures does not have a major effect on cells as determined by the various analyses, affecting only the proliferation stage. Thus, the microstructured titanium scaffolds direct the behaviour of pre-osteoblasts toward a mature state capable of mineralising the extracellular matrix. | ||||||||
| 6782 | 3.47 | 17052750 | 2007.05.03 | + | + | Effects of temperature on scope for growth and accumulation of Cd, Co, Cu and Pb by the marine bivalve Mytilus edulis. | Mar Environ Res | |
| VK Mubiana, R Blust, | ||||||||
| In many aquatic organisms including Mytilus edulis, the role of temperature on bioaccumulation of metals is still not clearly understood. In this study, uptake and accumulation of Cu, Co, Cd and Pb in mussels were investigated at different temperatures (6-26 degrees C). Results from exposure of isolated gills showed a positive relationship between temperature and metal uptake. But in whole organism experiments, only the accumulations of non-essential metals (Cd, Pb) showed a similar trend while the two essential metals Co and Cu were independent and inversely related to temperature, respectively. With exception of Cu, elimination process appeared to be independent of temperature. The study also showed that neither changes in scope for growth (SFG) of mussels nor chemical speciation could fully account for the observed temperature-effects. Overall, these results suggest that fundamentally (i.e. at epithelial membranes), temperature-effects on uptake are largely due to changes in solution chemistry and physical kinetics, which favours higher uptake at high temperature. But at whole organism level, complex physiological responses appears to mask the relationship, particularly for biologically essential metals like copper. | ||||||||
| 6783 | 3.46 | 10633173 | 2000.07.13 | + | + | Dose-response and threshold effects in cytotoxicity and apoptosis. | Mutat Res | |
| R Schulte-Hermann, B Grasl-Kraupp, W Bursch, | ||||||||
| Cell death can occur as an active, programmed event in response to cytotoxic injury or to endogenous growth limiting factors; the latter serve to maintain homeostasis of cell number in tissues. Cells seem to use different pathways for programmed death, as reflected by their different morphology and different biochemistry. Severe cell damage leading to incapacitation of essential cell functions such as ATP synthesis or the maintenance of membrane potential may lead to "necrosis". In any event, the incidence and rate of cell death increase with increasing signal intensity. Cytotoxic injury requires a certain number of primary insults; cell death will therefore occur only beyond a definable threshold. Growth factor control of cell death is receptor-mediated with dose-response relations including threshold phenomena follow the general principles of receptor kinetics. The occurrence of programmed cell death during the stages of carcinogenesis introduces a reversible component into this disease. Therefore, there may exist thresholds of dose or durations of exposure to certain carcinogens below which irreversible disease is not generated. | ||||||||
| 6784 | 3.46 | 18228238 | 2008.08.08 | + | + | Investigation of the inner environment of carbon nanotubes with a fullerene-nitroxide probe. | Small | |
| S Campestrini, C Corvaja, M De Nardi, C Ducati, L Franco, M Maggini, M Meneghetti, E Menna, G Ruaro, | ||||||||
| A fulleropyrrolidine bearing a nitroxide free radical has been inserted into single-walled carbon nanotubes with the aid of supercritical CO2. Thanks to the encapsulated paramagnetic probes, it has been possible to detect and characterize the resulting peapod-like structure through electron paramagnetic resonance (EPR) spectroscopy. In particular, the analysis of spectral parameters derived from extensive EPR studies has elucidated the orientation and the residual rotational dynamics of the molecules embedded in the nanotubes. A limited anisotropic rotational freedom of the encapsulated fullerene nitroxide reveals a rather strong interaction of the probe with the surrounding nanotube walls. The interaction seems to involve the fullerene cage (as confirmed by Raman spectroscopy) and not the nitroxide moiety, whose EPR spectral characteristics, such as the isotropic hyperfine constant and the g-tensor, remain unaltered after encapsulation. | ||||||||
| 6785 | 3.46 | 17110295 | 2007.03.01 | + | + | Long-term effects of exposure to particulate air pollution. | Clin Occup Environ Med | |
| J Schwartz, | ||||||||
| Considerable work has been done to elucidate the effects of polluted air, most of which has studied acute effects of particles. Studies suggest that the effects of longer term exposures are more than just the daily sum of the acute effects. Because most of the studies of acute effects have examined changes in health status occurring within days of the exposure, this article takes a broad definition of long-term exposure to include averaging times of months to years. It concludes that health effects increase as length of exposure increases, but much of that increase occurs within the first year. | ||||||||
| 6786 | 3.45 | 9539973 | 1998.05.05 | + | + | Evaluation of the genotoxic properties of paraquat in V79 Chinese hamster cells. | Mutat Res | |
| G Speit, S Haupter, A Hartmann, | ||||||||
| The genotoxic potential of the herbicide paraquat (PQ), an intracellular generator of superoxide, was comparatively tested in various genotoxicity tests with V79 Chinese hamster cells. PQ clearly induced cytotoxicity and chromosome aberrations but did not induce gene mutations at the HPRT locus or increased DNA migration in the comet assay under the same treatment conditions. Using a modified comet assay protocol with formamidopyrimidine-DNA glycosylase (FPG) protein, a DNA repair enzyme which specifically nicks DNA at sites of 8-oxo-guanines and formamidopyrimidines, we could not detect oxidative DNA base damage after PQ treatment. When cells were treated directly on the slides after lysis (i.e, after the cell membrane barrier was eliminated), increased DNA migration was observed after treatment with high PQ-concentrations. Our results suggest that PQ does not significantly induce DNA lesions relevant for HPRT gene mutations in cultivated V79 cells. Since PQ-induced chromosome aberrations only occur after treatment with high concentrations which totally prevent cell survival and are not preceded by an induction of DNA strand breakage in intact cells, their biological significance has to be questioned. | ||||||||
| 6787 | 3.45 | 9400748 | 1998.01.30 | + | + | Relevance of particle-induced rat lung tumors for assessing lung carcinogenic hazard and human lung cancer risk. | Environ Health Perspect | |
| JL Mauderly, | ||||||||
| Rats and other rodents are exposed by inhalation to identify agents that might present hazards for lung cancer in humans exposed by inhalation. In some cases, the results are used in attempts to develop quantitative estimates of human lung cancer risk. This report reviews evidence for the usefulness of the rat for evaluation of lung cancer hazards from inhaled particles. With the exception of nickel sulfate, particulate agents thought to be human lung carcinogens cause lung tumors in rats exposed by inhalation. The rat is more sensitive to carcinogenesis from nonfibrous particles than mice or Syrian hamsters, which have both produced false negatives. However, rats differ from mice and nonhuman primates in both the pattern of particle retention in the lung and alveolar epithelial hyperplastic responses to chronic particle exposure. Present evidence warrants caution in extrapolation from the lung tumor response of rats to inhaled particles to human lung cancer hazard, and there is considerable uncertainty in estimating unit risks for humans from rat data. It seems appropriate to continue using rats in inhalation carcinogenesis assays of inhaled particles, but the upper limit of exposure concentrations must be set carefully to avoid false-positive results. A positive finding in both rats and mice would give greater confidence that an agent presents a carcinogenic hazard to man, and both rats and mice should be used if the agent is a gas or vapor. There is little justification for including Syrian hamsters in assays of the intrapulmonary carcinogenicity of inhaled agents. | ||||||||
| 6788 | 3.45 | 16169046 | 2006.04.27 | + | + | Evaluation of the phytotoxicity of contaminated sediments deposited "on soil": II. Impact of water draining from deposits on the development and physiological status of neighbouring plants at growth stage. | Chemosphere | |
| JP Bedell, A Briant, C Delolme, L Lassabatère, Y Perrodin, | ||||||||
| As part of a study of the phytotoxic risk of spreading contaminated sediments "on soil", a laboratory experiment was carried out to assess the impact of water draining from sediments on peripheral vegetation. Drainage water was obtained in the laboratory by settling three sediments with different pollutants levels, and the supernatant solutions (respectively A1, B1, C1 drainage waters) were used as soaking water for maize (Zea maïs L.) and ryegrass (Lolium perenne L.). The physicochemical characteristics of the supernatant water, particularly metal contents, showed a pattern of contamination, with C1>A1>B1. The plants tested were grown on soil for 21 days, before being soaked for another 21-day period with drainage water (treatments) and distilled water (control). Biomass parameters (fresh weight, length, etc.), enzymatic activity [glutamine synthetase (GS), phosphoenolpyruvate carboxylase (PEPc)] and Zn, Cu, Cd and Cr contents were measured on both the shoots and roots of each plant. Biomass parameters were stimulated by C1, not affected by A1 and decreased with B1 for maize, whereas they increased for ryegrass in all the treatments. Compared to the control, GS activity was stimulated by C1 in the shoots of both plants and inhibited by treatments B1 and C1 in maize roots. PEPc activity in ryegrass was 1.5-5 times higher with contaminated water treatment, while contrasting effects were observed in maize plants. Both plants showed greater accumulation of chromium and zinc than cadmium and copper. Treatment A1 was found to be less active on plant growth and have a lower impact on the physiological status (enzymatic activities) of both plants. Treatment C1 stimulated the growth and physiological status of the plants, especially in shoots, with higher metal accumulation values in both plants. Treatment B1 was found to show more variable effects on growth indices, enzymatic activity and metal accumulation according to plant species. | ||||||||
| 6789 | 3.45 | 16853418 | 2007.07.24 | + | + | Metalated diblock and triblock poly(ethylene oxide)-block-poly(4-vinylpyridine) copolymers: understanding of micelle and bulk structure. | J Phys Chem B | |
| LM Bronstein, SN Sidorov, V Zhirov, D Zhirov, YA Kabachii, SY Kochev, PM Valetsky, B Stein, OI Kiseleva, SN Polyakov, EV Shtykova, EV Nikulina, DI Svergun, AR Khokhlov, | ||||||||
| The paper provides new insights into the structure of Pt-containing diblock and triblock copolymers based on poly(ethylene oxide) (PEO) and poly(4-vinylpyridine) (P4VP), using a combination of atomic force microscopy (AFM), X-ray diffraction (XRD), transmission electron microscopy (TEM), and anomalous small-angle X-ray scattering (ASAXS). Parallel studies using methods contributing supplemental structural information allowed us to comprehensively characterize sophisticated polymer systems during metalation and to exclude possible ambiguity of the data interpretation of each of the methods. AFM and TEM make available the determination of sizes of the micelles and of the Pt-containing micelle cores, respectively, while a combination of XRD, TEM, and ASAXS reveals Pt-nanoparticle size distributions and locations along with the structural information about the polymer matrix. In addition, for the first time, ASAXS revealed the organization of Pt-nanoparticle-filled diblock and triblock copolymers in the bulk. The nanoparticle characteristics are mainly determined by the type of block copolymer system in which they are found: larger particles (2.0-3.0 nm) are formed in triblock copolymer micelles, while smaller ones (1.5-2.5 nm) are found in diblock copolymer micelles. This can be explained by facilitated intermicellar exchange in triblock copolymer systems. For both systems, Pt nanoparticles have narrow particle size distributions as a result of a strong interaction between the nanoparticle surface and the P4VP units inside the micelle cores. The pH of the medium mainly influences the particle location rather than the particle size. A structural model of Pt-nanoparticle clustering in the diblock PEO-b-P4VP and triblock P4VP-b-PEO-b-P4VP copolymers in the bulk was constructed ab initio from the ASAXS data. This model reveals that nearly spherical micellar cores of about 10 nm in diameter (filled with Pt nanoparticles) aggregate forming slightly oblate hollow bodies with an outer diameter of about 40 nm. | ||||||||
| 6790 | 3.45 | 17579752 | 2007.09.11 | + | + | Surface modification of resorcinarene based self-assembled solid lipid nanoparticles for drug targeting. | Chem Commun (Camb) | |
| S Ehrler, U Pieles, A Wirth-Heller, P Shahgaldian, | ||||||||
| Prolyl-bearing amphiphilic resorcinarenes, e.g. tetrakis(N-methylprolyl)tetraundecylcalix[4]resorcinarene, self-assemble as stable solid lipid nanoparticles; these fully characterized systems could be further functionalized at their surface with proteins, and interact with specific antibodies bound on a sensor surface. | ||||||||
| 6791 | 3.45 | 15461485 | 2006.04.25 | + | + | Interfacial micellar structures from novel amphiphilic star polymers. | Langmuir | |
| KL Genson, J Hoffman, J Teng, ER Zubarev, D Vaknin, VV Tsukruk, | ||||||||
| An amphiphilic heteroarm star polymer containing 12 alternating hydrophobic/hydrophilic arms of polystyrene (PS) and poly(acrylic acid) (PAA) connected to a well-defined rigid aromatic core was studied at the air-water and the air-solid interfaces. At the air-water interface, the molecules spontaneously form pancakelike micellar aggregates which measure up to several microns in diameter and 5 nm in thickness. Upon reduction of the surface area per molecule to 7 nm2, the two-dimensional micelles merged into a dense monolayer. We suggest that confined phase separation of dissimilar polymer arms occurred upon their segregation on the opposite sides of the rigid disklike aromatic core, forcing the rigid cores to adopt a face-on orientation with respect to the interface. Upon transfer onto solid supports the PS chains face the air-film interface making it completely hydrophobic, and the PAA chains were found to collapse and form a thin flattened underlayer. This study points toward new strategies to create large 2D microstructures with facial amphiphilicity and suggests a profound influence of star molecular architecture on the self-assembly of amphiphiles at the air-water interface. | ||||||||
| 6792 | 3.44 | 17416197 | 2007.05.03 | + | + | Cytotoxicity evaluation of anionic nanoliposomes and nanolipoplexes prepared by the heating method without employing volatile solvents and detergents. | Pharmazie | |
| MR Mozafari, CJ Reed, C Rostron, | ||||||||
| Submicron lipid vesicles (nanoliposomes) are being used as carriers of bioactive compounds. In addition, complexes of nanoliposomes and nucleic acids (nanolipoplexes) are promising tools for the treatment of cancer, and viral and genetic disorders. Toxicity of some of these formulations, however, still remains a concern in their clinical utilisation. To address this problem, anionic liposomes were prepared by two different techniques, the conventional thin-film method, and the heating method (HM), in which no volatile organic solvent or detergent is used. An anionic nanolipoplex was constructed by incorporating plasmid DNA (pcDNA3.1/His B/lacZ) into the HM-nanoliposomes by the mediation of calcium. The toxicity of the nanoliposomes, with and without plasmid and Ca2+, was assessed using a human bronchial epithelial cell line (16HBE14o-) in the presence of serum. Cytotoxicity evaluations performed by two different assays (i.e. NRU and MTT) indicated that HM-nanoliposomes were completely non-toxic in the cell-line tested, whereas conventional liposomes revealed significant levels of toxicity. This may be due to the presence of trace amounts of chloroform and/or methanol applied during their preparation. Similar results were obtained for different sizes of lipid vesicles (prepared by 100 nm and 400 nm pore-size filters). In addition, it was observed that incorporation of DNA (15 microg/ 285 microg lipid) and Ca2+ (50 mM) to the nanoliposomes did not have any effect on their cytotoxicities. These findings indicate that the HM-liposomes have great potential as non-toxic delivery vehicles in human gene therapy and drug delivery applications while liposomes made using organic solvents should be used with caution. | ||||||||
| 6793 | 3.44 | 12966974 | 2003.12.16 | + | + | Forces between colloid particles in natural waters. | Environ Sci Technol | |
| LM Mosley, KA Hunter, WA Ducker, | ||||||||
| The origin and nature of interparticle forces acting on colloid surfaces in natural waters has been examined using an atomic force microscope. Natural colloids were represented by a surface film of iron oxide precipitated onto spherical SiO2 particles, and the effects of adsorbed natural organic matter (NOM), solution pH, and ionic composition on the force-separation curves were investigated. NOM from both riverine and marine environments was strongly adsorbed to the iron oxide surface. Under conditions of low ionic strength, the interparticle forces were dominated by electrostatic repulsion arising from negative functional groups on the NOM, except at very small separations (<10 nm) where repulsive forces arising from steric interference of the NOM molecules were also present. At high ionic strength (e.g., seawater) or low pH, the electrostatic forces were largely absent, allowing steric repulsion forces to dominate. In addition, adhesive bridging between surfaces by adsorbed NOM was observed, creating a strong energy barrier to spontaneous disaggregation of colloid aggregates. Our results demonstrate that adsorbed NOM dominates the surface forces and thus stability with respect to aggregation of natural water colloids. | ||||||||
| 6794 | 3.44 | 14720481 | 2008.01.03 | + | + | Antioxidant responses to benzo[a]pyrene and Aroclor 1254 exposure in the green-lipped mussel, Perna viridis. | Environ Pollut | |
| CC Cheung, WH Siu, BJ Richardson, SB De Luca-Abbott, PK Lam, | ||||||||
| In this study, the green-lipped mussel, Perna viridis (L.), was exposed to two concentrations of benzo[a]pyrene (B[a]P) (0.3 microg l(-1); 3 microg l(-1)) and two concentrations of Aroclor 1254 (0.5 microg l(-1); 5 microg l(-1)). In addition, a mixture of the contaminants was used (0.3 microg l(-1) B[a]P+0.5 microg l(-1) Aroclor 1254; 3 microg l(-1) B[a]P+5 microg l(-1) Aroclor 1254). All concentrations were nominal. A suite of enzymes [glutathione S transferase (GST), superoxide dismutase (SOD), catalase (CAT), glutathione peroxidase (GPx), glutathione reductase (GR)], glutathione (GSH) level and lipid peroxidation (LPO) in the mussel gill and hepatopancreas were monitored over 18 days. CAT and GSH in gill tissue were positively correlated with concentration of Aroclor 1254. Activity of hepatic GST and SOD was significantly related to body burden of Aroclor 1254. LPO, GR and GPx in gill and hepatopancreas and hepatic GST were positively correlated with B[a]P concentration. The results indicate the importance of using biomarkers specific to the type of contaminant(s) that are likely to be present. Controlled laboratory experiments, such as this study, are useful in ascertaining biomarkers suitable for use with complex contaminant mixtures in the marine environment. | ||||||||
| 6795 | 3.44 | 18654354 | 2008.09.10 | + | Atomic motion in ferromagnetic break junctions. | Nat Nanotechnol | ||
| SF Shi, DC Ralph, | ||||||||
| 6796 | 3.44 | 18654248 | 2008.09.10 | + | + | Quantized magnetoresistance in atomic-size contacts. | Nat Nanotechnol | |
| A Sokolov, C Zhang, EY Tsymbal, J Redepenning, B Doudin, | ||||||||
| When the dimensions of a metallic conductor are reduced so that they become comparable to the de Broglie wavelengths of the conduction electrons, the absence of scattering results in ballistic electron transport and the conductance becomes quantized. In ferromagnetic metals, the spin angular momentum of the electrons results in spin-dependent conductance quantization and various unusual magnetoresistive phenomena. Theorists have predicted a related phenomenon known as ballistic anisotropic magnetoresistance (BAMR). Here we report the first experimental evidence for BAMR by observing a stepwise variation in the ballistic conductance of cobalt nanocontacts as the direction of an applied magnetic field is varied. Our results show that BAMR can be positive and negative, and exhibits symmetric and asymmetric angular dependences, consistent with theoretical predictions. | ||||||||
| 6797 | 3.44 | 9055957 | 1997.05.15 | + | + | Toxicity in vitro of some silicon carbides and silicon nitrides: whiskers and powders. | Am J Ind Med | |
| I Svensson, E Artursson, P Leanderson, R Berglind, F Lindgren, | ||||||||
| The objectives of this work were to investigate the toxicity of silicon carbide whiskers and powders and silicon nitride whiskers and powders and to compare their toxicity with the toxicity of crocidolite. The effects studied were inhibition of the cloning efficiency of V79 cells, formation of DNA strand breaks by means of a nick translation assay, formation of oxygen radicals in three different assays, and the ability to stimulate neutrophils to produce hydroxyl radicals. All materials showed concentration-dependent inhibition of the cloning efficiency of V79 cells. The inhibition by the most toxic whiskers was in the same order of magnitude as that of crocidolite. Milled whiskers and powders were less toxic than the whiskers. There was a high DNA breaking potential for crocidolite and four of the silicon carbide whiskers and a rather low one for the other materials. Formation of hydroxyl radicals was found for crocidolite and one of the silicon carbide whiskers. In the neutrophil activation test, there was a great variation in the different materials' abilities to activate neutrophils. There was also a good correlation between chemiluminescence and H2O2 formation. The highest activation was found in neutrophils exposed to two of the silicon carbide whiskers and one milled whisker. The conclusion of the investigation is that some of the ceramic materials studied had damaging biological effects comparable to or greater than those of crocidolite. The results from the investigation clearly imply that caution is needed in the introduction of new ceramic fiber materials, so that the correct precautions and protective devices are used in order to avoid harm to the personnel handling the material. | ||||||||
| 6798 | 3.44 | 12960411 | 2004.06.09 | + | + | DNA binding of polycyclic aromatic hydrocarbons in a human bronchial epithelial cell line treated with diesel and gasoline particulate extracts and benzo[a]pyrene. | Mutagenesis | |
| SK Pohjola, M Lappi, M Honkanen, L Rantanen, K Savela, | ||||||||
| Particulate matter of vehicle exhaust is known to contain carcinogenic compounds such as polycyclic aromatic hydrocarbons (PAH) and is suggested to increase lung cancer risk in humans. This study examines the differences in diesel and gasoline-derived PAH binding to DNA in a human bronchial epithelial cell line (BEAS-2B). Particulate matter (PM) of gasoline exhaust was collected from passenger cars on filters and semi-volatile compounds on polyurethane foam (PUF). The soluble organic fraction (SOF) extracted from the particles was used to expose the cells and to perform PAH analysis. Gasoline extracts, benzo[a]pyrene (B[a]P) and reference materials (SRM 1650 and 1587) were used to study dose-dependent adduct formation in BEAS-2B cells. The levels of DNA adducts were in good accord with the 10 DNA adduct-forming PAH concentrations analyzed in the extracts. Gasoline extracts, SRM 1650, SRM 1587 and B[a]P formed DNA adducts dose-dependently in BEAS-2B cells. The time-dependent DNA adduct formation of 5.0 micro M B[a]P was lower than that of 2.5 micro M B[a]P. The results of this study indicate that reformulated and standard diesel fuels formed about 11- and 31-fold more adducts than gasoline, respectively, when PAH-DNA adduct levels were calculated on an emission basis (adducts/mg PM/km), whereas on a particulate basis (adducts/mg PM) no difference between the diesel and gasoline extracts was observed. We conclude that the genotoxicity of diesel fuel is based on higher particulate emission rates compared to gasoline emission and although the concentration of PAH compounds was higher in diesel particulate extracts, DNA binding by the gasoline particulate-bound PAH compounds was more pronounced than that by the diesel particulate-bound PAH compounds. | ||||||||
| 6799 | 3.43 | 16646067 | 2006.09.12 | + | + | Silicon addition to hydroxyapatite increases nanoscale electrostatic, van der Waals, and adhesive interactions. | J Biomed Mater Res A | |
| J Vandiver, D Dean, N Patel, C Botelho, S Best, JD Santos, MA Lopes, W Bonfield, C Ortiz, | ||||||||
| The normal intersurface forces between nanosized probe tips functionalized with COO(-)-terminated alkanethiol self-assembling monolayers and dense, polycrystalline silicon-substituted synthetic hydroxyapatite (SiHA) and phase pure hydroxyapatite (HA) were measured via a nanomechanical technique called chemically specific high-resolution force spectroscopy. A significantly larger van der Waals interaction was observed for the SiHA compared to HA; Hamaker constants (A) were found to be A(SiHA) = 35 +/- 27 zJ and A(HA) = 13 +/- 12 zJ. Using the Derjaguin-Landau-Verwey-Overbeek approximation, which assumes linear additivity of the electrostatic double layer and van der Waals components, and the nonlinear Poisson-Boltzmann surface charge model for electrostatic double-layer forces, the surface charge per unit area, sigma (C/m(2)), was calculated as a function of position for specific nanosized areas within individual grains. SiHA was observed to be more negatively charged than HA with sigma(SiHA) = -0.024 +/- 0.013 C/m(2), two times greater than sigma(HA) = -0.011 +/- 0.006 C/m(2). Additionally, SiHA was found to have increased surface adhesion (0.7 +/- 0.3 nN) compared to HA (0.5 +/- 0.3 nN). The characterization of the nanoscale variations in surface forces of SiHA and HA will enable an improved understanding of the initial stages of bone-biomaterial bonding. | ||||||||
| 6800 | 3.43 | 17112249 | 2007.06.28 | + | + | Size-controllable fabrication of noble metal nanonets using a TiO2 template. | Inorg Chem | |
| L Yang, Q Cai, Y Yu, | ||||||||
| We present herein a simple template method for preparing noble metal nanonets with defined sizes. The template utilized is a TiO2 nanotube (NT) array prepared by anodic oxidation of a pure titanium sheet in an electrolyte solution containing sodium fluoride. Uniform NTs with defined sizes are obtained by controlling the anodic potential. Gold nanonets are prepared by electrodepositing gold onto the template and then dissolving the TiO2 template in a 0.2 M HF solution. The pore size of the gold nanonet is determined by the TiO2 NT hole size. The formation mechanism of the nanonet is elucidated from field-emission scanning electron microscopy and transmission electron microscopy. Although a lot of reports have been presented on the synthesis of nanostructure materials, no work has been reported on the template synthesis of gold nanonets. This paper gives a simple and universal way to prepare noble metal nanonets. | ||||||||
| 6801 | 3.43 | 15559853 | 2005.03.14 | + | + | Incorporation of polymer microspheres within fibrin scaffolds for the controlled delivery of FGF-1. | J Biomater Sci Polym Ed | |
| SM Royce, M Askari, KG Marra, | ||||||||
| The purpose of this work was to examine the feasibility of a hybrid scaffold in which fibroblast growth factor-1 (FGF-1)-encapsulated microspheres are embedded within a fibrin gel. Such a tissue-engineered scaffold could be incorporated into surgical procedures to promote healing while simultaneously delivering therapeutic agents that promote angiogenesis. Fibrin has been extensively studied as an adhesive in plastic and reconstructive surgery and the enhancement of wound healing with embedded growth factors is desirable. We report the release of a fluorescently-labeled model protein, bovine serum albumin (BSA-FITC), from poly(D,L-lactic-co-glycolic acid) microspheres embedded in the fibrin scaffold. The protein release was found to be significantly delayed as compared to microspheres alone during the initial 24 h of release. Additionally, FGF-1 was examined for efficient incorporation into these scaffolds as a potential mitogen for fibroblasts. The optimal concentration of FGF-1 in the media that enhanced NIH-3T3 fibroblast proliferation over 48 h was determined to be 0.1 microg/ml. The release of FGF-1 from microspheres embedded in fibrin gels was compared to FGF-1-encapsulated microspheres alone. The release of FGF-1 from the microsphere/scaffolds was delayed as compared to the release of FGF-1 from microspheres alone. This novel hybrid fibrin/microsphere scaffold is a feasible delivery system for growth factors. | ||||||||
| 6802 | 3.43 | 15994132 | 2006.01.04 | + | + | A non-radioactive, PFGE-based assay for low levels of DNA double-strand breaks in mammalian cells. | DNA Repair (Amst) | |
| I Gradzka, T Iwaneńko, | ||||||||
| A PFGE method was adapted to measure DNA double-strand breaks (DSBs) in mammalian cells after low (0-25 Gy) doses of ionising radiation. Instead of radionuclide incorporation, DNA staining in the gel by SYBR-Gold was used, which lowered the background of DNA damage and could be applied to non-cycling cells. DSB level was defined as a product of a fraction of DNA released to the gel (FR) and a number of DNA fragments in the gel (DNA(fragm)) and expressed as a percentage above control value. The slope of the dose-response curve was two-fold higher compared to that with FR alone as DSB level indicator (31.4 versus 15.6% per Gy). Two alternative ways were proposed to determine the total amount of DNA, used for FR calculation: measurement of DNA content in a plug not subjected to electrophoresis, with the use of Pico-Green, or estimation of DNA released to the gel from a plug irradiated with 600 Gy of gamma-rays. The limit of DSB detection was 0.25 Gy for human G1-lymphocytes and 0.5-1 Gy for asynchronous cultures of human glioma M059 K and J or mouse lymphoma L5178Y-R and -S cells. Specificity of our PFGE assay to DSB was confirmed by the fact that no damage was detected after treatment of the cells with H(2)O(2), an inducer of single-strand DNA breaks (SSBs). On the contrary, the H(2)O(2) inflicted damage was detected by neutral comet assay, attaining 160% above control (equivalent to 2.5 Gy of X-radiation). DSB rejoining, measured in cells after X-irradiation with a dose of 10 Gy, generally proceeded faster than that measured previously after higher (30-50 Gy) doses of ionising radiation. Clearly seen were defects in DSB rejoining in radiosensitive M059 J and L5178Y-S cells compared to their radioresistant counterparts, M059 K and L5178Y-R. In some cell lines, a secondary post-irradiation increase in DSB levels was observed. The possibility is considered that these additional DSBs may accumulate during processing of non-DSB clustered DNA damage or/and represent early apoptotic events. | ||||||||
| 6803 | 3.43 | 17996885 | 2008.03.20 | + | + | Surfactant-promoted formation of fractal and dendritic nanostructures of gold and silver at the organic-aqueous interface. | J Colloid Interface Sci | |
| VV Agrawal, GU Kulkarni, CN Rao, | ||||||||
| The effect of surfactants such as tetraoctylammoniumbromide (TOAB) and cetyltrimethylammoniumbromide (CTAB) on the type of nanostructures formed when gold ions present in the organic phase are reduced at the interface by hydrazine in the aqueous phase has been investigated. Extended fractal structures are formed at the liquid-liquid interface, the fractal structures themselves comprising cauliflower type units formed by gold nanorods. Accordingly, the nanostructures exhibit transverse and longitudinal plasmon adsorption bands in the 550 and 800 nm regions, respectively. Dendritic structures of silver are formed at the interface when Ag ions are reduced similarly in the presence of surfactants. The nanostructures consist of nanoparticles or nanorods with five-fold symmetry. | ||||||||
| 6804 | 3.43 | 18247568 | 2008.04.15 | + | + | Heterobifunctional poly(ethylene oxide) oligomers containing carboxylic acids. | Biomacromolecules | |
| ML Vadala, MS Thompson, MA Ashworth, Y Lin, TP Vadala, R Ragheb, JS Riffle, | ||||||||
| Syntheses of vinylsilyl alcohols having one to three vinyl moieties and their use as initiators for ethylene oxide polymerizations are discussed. Poly(ethylene oxide) oligomers with vinylsilanes at one end and a hydroxyl group at the other were prepared in base-catalyzed reactions. Molecular weights determined from 1H NMR and gel permeation chromatography were close to the targeted values. Carboxylic acid functional poly(ethylene oxide) oligomers were prepared from ene-thiol addition reactions of mercaptoacetic acid across the vinylsilane terminus. It is anticipated that these carboxylic acid functional oligomers will complex to magnetite nanoparticles to afford complexes that can be dispersed in aqueous media. | ||||||||
| 6805 | 3.43 | 17718981 | 2007.09.20 | + | Novel ternary polyplex of triblock copolymer, pDNA and anionic dendrimer phthalocyanine for photochemical enhancement of transgene expression. | J Control Release | ||
| A Arnida, N Nishiyama, WD Jang, Y Yamasaki, K Kataoka, | ||||||||
| 6806 | 3.42 | 17459469 | 2007.07.18 | + | + | Glycoconjugated peptide dendrimers-based nanoparticulate system for the delivery of chloroquine phosphate. | Biomaterials | |
| P Agrawal, U Gupta, NK Jain, | ||||||||
| Dendrimers consisting of different molecules of metabolic pathways such as amino acids can greatly reduce the toxicity associated with amine-terminated dendrimers e.g. polyamidoamine (PAMAM) and polypropylene imine (PPI) dendrimers. In the present study, poly-L-lysine dendrimers having polyethyleneglycol (PEG-1000) as core, were synthesized upto fourth generation. Dendrimers were synthesized by alternating protection and deprotection steps of L-lysine by di-BOC (di-tertiary butyl pyrocarbonate) till the formation of 4.0 G peptide dendrimer took place. D-galactose was selected as model sugar for peripheral conjugation (coating) of these peptide dendrimer. The complete formation of uncoated and galactose-coated poly-L-lysine dendrimers was characterized by transmission electron microscopy (TEM), IR, NMR and MALDI TOF mass spectroscopic studies. Chloroquine phosphate (CP)-loaded uncoated and coated dendrimers were evaluated for in vitro drug release rate, hemolytic toxicity and stability studies. Ex vivo cellular uptake studies of uncoated and coated drug dendrimer formulations in macrophages revealed almost 5 times reduced phagocytosis due to galactose coating (p<0.0001). In vitro-in vivo release behavior indicated possibilities of galactose-coated drug dendrimers formulation in controlled drug delivery of CP. Galactose coated formulations drastically reduced hemolytic toxicity compared to uncoated poly-L-lysine formulation as well as plain drug. Hematological data suggests that galactose-coated formulations are less immunogenic compared to uncoated formulations. Finally, it can be concluded that galactose-coated polylysine dendrimers can be utilized for controlled delivery of CP more safely compared to its uncoated formulation both in vitro and in vivo. | ||||||||
| 6807 | 3.42 | 17658861 | 2007.09.17 | + | + | Adsorption processes of Gly and Glu amino acids on hydroxyapatite surfaces at the atomic level. | Langmuir | |
| H Pan, J Tao, X Xu, R Tang, | ||||||||
| The regulation mechanism of organic additives on the crystallization of inorganic crystal is fundamentally important in biomineralization. Experimentally, it was found that the amino acids glycine (Gly) and glutamic acid (Glu) could lead to the formation of rod- and plate-like hydroxyapatite (HAP) crystallites, respectively. The detailed adsorption behavior of Gly and Glu on HAP crystal faces was studied by molecular dynamics (MD) simulation. The specific adsorption sites and patterns of Gly and Glu on the (100) and (001) faces of HAP crystals were revealed at the atomic level. The amino acids adsorbed on the HAP (001) and (100) faces with their positive amino groups occupied vacant calcium sites, and their negative carboxylate groups occupied vacant P or OH sites precisely and formed an ordered adsorption layer. The atomic force microscopy pulling simulation and free energy calculation showed that Glu was much more difficult to depart from the HAP (001) face than that from the (100) face. This result indicated that Glu preferred to adsorb strongly onto the HAP (001) face, which resulted in the formation of plate-like HAP. However, Gly did not show any significantly preferential adsorption between these two HAP faces. Thus, the habits of HAP, rod-like crystallites, were not altered during the HAP crystallization in the presence of Gly. Combined with experimental results, our study demonstrated that the MD simulation of interfacial structures could improve our understanding of biological regulation in mineralization processes at the atomic level. | ||||||||
| 6808 | 3.42 | 15840534 | 2005.10.26 | + | + | How to accurately assay the algal toxicity of pesticides with low water solubility. | Environ Pollut | |
| J Ma, J Chen, | ||||||||
| A novel method for assaying and calculating the toxicity of water-insoluble pesticides to green algae has been put forward in this work. First, a solvent is selected for use in bioassays; there should be a detailed screening to identify a solvent with inherently low toxicity to the test organism. Second, the EC50 is determined for selected pesticides by measuring the toxicity of various concentrations of each of the selected pesticides in a fixed concentration of selected solvent. Third, concentrations of the selected solvent are varied and the EC50 of each pesticide tested is assayed at a fixed concentration. Fourth, several suitable groups of solvent concentrations are selected and the corresponding EC50 values of tested pesticides are considered to establish the linear regression equation. Letting the solvent concentration be zero, one calculates the corresponding EC50 value, which corresponds to the inherent toxicity of the tested pesticide. | ||||||||
| 6809 | 3.42 | 15839564 | 2005.07.15 | + | + | Importance of acclimation to environmentally relevant zinc concentrations on the sensitivity of Daphnia magna toward zinc. | Environ Toxicol Chem | |
| BT Muyssen, CR Janssen, | ||||||||
| Daphnia magna was acclimated for six generations to an acclimation range of 0.02 to 74 microg/L of Zn2+. This range was determined by combining physicochemical water characteristics of European surface waters with total Zn concentrations in these waters in such a way that they resulted in minimal and maximal free (i.e., assumed bioavailable) Zn ion activities. No significant differences were found in acute Zn tolerance between the different acclimation concentrations: Average 48-h median effective concentration (EC50) values ranged from 608+/-94 to 713+/-249 microg/L of Zn2+. Also, no significant shifts in chronic tolerance were observed: Average 21-d EC50 (based on net reproductive rate) ranged from 91+/-20 to 124+/-22 microg/L of Zn2+. However, at test concentrations less than the 21-d EC50, acclimation significantly increased the reproductive capacity of the offspring produced. This indicates that metal acclimation is not necessarily accompanied by an increase in tolerance but also may manifest in other responses (e.g., reproduction rate). Organisms acclimated to a range from 6 to 22 microg/L of Zn2+ produced significantly more offspring than organisms acclimated to lower and higher Zn concentrations in test concentrations up to 50 microg/L of Zn2+. This range corresponds to a previously established optimal concentration range for D. magna. Bioconcentration factors indicated that Zn was actively regulated in the acclimation range tested. | ||||||||
| 6810 | 3.42 | 18380509 | 2008.06.11 | + | + | Chemical force titration of plasma polymer-modified PDMS substrates by using plasma polymer-modified AFM tips. | Langmuir | |
| A Geissler, MF Vallat, L Vidal, JC Voegel, J Hemmerlé, P Schaaf, V Roucoules, | ||||||||
| Plasma polymerization has gained increasing attention in surface functionalization. We use here chemical force titration to characterize PDMS (polydimethylsiloxane) substrates modified by maleic anhydride-pulsed plasma polymerization. The coating is hydrolyzed to promote the formation of dicarboxylic acid groups. To enhance the variation of the adhesion forces as a function of pH, we use AFM tips modified in the same way as the substrates. The pH-dependent adhesion measurements are performed at different KCl concentrations. The dicarboxylic nature of the maleic acid groups clearly emerges from the force titration curves. The surface pK(a) values (pK(a1) = 3.5 +/- 0.5 and pK(a2) = 9.5 +/- 0.5) of the dicarboxylic acids are evaluated from low electrolyte concentration solutions. The values are shifted toward higher pK(a) values when compared to maleic acid in solution. The first pK(a) appears in the titration force curve for low salt concentration as a peak. This peak changes to a sigmoidal shape at higher salt concentrations. The appearance of a peak is attributed to the formation of strong hydrogen bonds between the tip and the substrate as reported in the literature. The effect of the ionic strength on the force curves is explained by the condensation of counterions on the carboxylate groups. At high pH, the adhesion force almost vanishes. On the approach, at high pH, one first observes repulsion between the tip and the substrate, which varies exponentially with the tip/substrate distance. The decay length of this repulsion force is in good agreement with theoretical predictions of the Debye length, attesting to the electrostatic nature of the interactions. We also find that the replacement of monovalent cation K(+) by the divalent cation Ca(2+) leads to significant changes in the force titration curve at high pH where the dicarboxylic groups are fully ionized. We observe that the adhesion force no longer vanishes at high pH but even slightly increases with pH, an effect that is explained by Ca(2+) ions bridging between two carboxylate groups. | ||||||||
| 6811 | 3.42 | 15570962 | 2005.02.07 | + | + | Graphitic carbon nanofiber (GCNF)/polymer materials. I. GCNF/epoxy monoliths using hexanediamine linker molecules. | J Nanosci Nanotechnol | |
| WH Zhong, J Li, LR Xu, JA Michel, LM Sullivan, CM Lukehart, | ||||||||
| Processing methods have been optimized for the formation of graphitic carbon nanofiber (GCNF)/epoxy nanocomposites containing GCNFs highly dispersed throughout a thermoset epoxy matrix. GCNFs having a herringbone atomic structure are surface-derivatized with bifunctional hexanediamine linker molecules (GCNF-HDA) capable of covalent binding to an epoxy matrix during thermal curing and are cut to smaller dimension using high-power ultrasonication. GCNF-HDA nanofibers are dispersed in epoxy resin at 0.3 wt.% loading using variable levels of ultrasonication processing prior to thermal curing. Effects of sonication power on the quality of the GCNF-HDA/epoxy material obtained after curing have been determined from flexural property measurements, thermomechanical analysis and SEM/TEM imaging. GCNF-HDA/epoxy material of the highest quality is obtained using low-power sonication, although high-power sonication for short periods gives improved flexural properties without lowering the glass transition temperature. Good dispersion and polymer wetting of the GCNF component is evident on the nanoscale. | ||||||||
| 6812 | 3.41 | 17944524 | 2008.01.09 | + | + | Tunability of the refractive index of gold nanoparticle dispersions. | Nano Lett | |
| S Kubo, A Diaz, Y Tang, TS Mayer, IC Khoo, TE Mallouk, | ||||||||
| Alkanethiol-capped gold nanoparticles dispersed in n-dodecane were studied by spectroscopic ellipsometry and were modeled using Mie scattering theory. The refractive index in the visible and near-infrared depended on the volume fraction of gold nanoparticles, in good agreement with the theoretical expectation that such dispersed plasmonic nanoparticles can act as low or tunable refractive index materials at specific optical wavelengths. | ||||||||
| 6813 | 3.41 | 8391338 | 1993.08.03 | + | + | The importance of hydrophobicity in the mutagenicity of methanesulfonic acid esters with Salmonella typhimurium TA100. | Chem Res Toxicol | |
| AK Debnath, C Hansch, | ||||||||
| The analysis of the mutagenic activity of a series of 15 methanesulfonate esters with Salmonella typhimurium TA100 shows that it can be correlated with the following equation: log TA100 = 1.10 log P + 0.73 log MMI -2.53, where MMI is the relative rate of reaction of the esters with N-methyl-2-mercaptoimidazole and P is the octanol/water partition coefficient. The results are compared with a number of other structure-activity studies on mutagenesis by a variety of types of chemicals. | ||||||||
| 6814 | 3.41 | 18174958 | 2008.03.20 | + | + | Low-level exposure to multiple chemicals: reason for human health concerns? | Environ Health Perspect | |
| A Kortenkamp, M Faust, M Scholze, T Backhaus, | ||||||||
| BACKGROUND: A key question in the risk assessment of exposures to multiple chemicals is whether mixture effects may occur when chemicals are combined at low doses which individually do not induce observable effects. However, a systematic evaluation of experimental studies addressing this issue is missing. OBJECTIVES: With this contribution, we wish to bridge this gap by providing a systematic assessment of published studies against well-defined quality criteria. RESULTS: On reviewing the low-dose mixture literature, we found good evidence demonstrating significant mixture effects with combinations of chemicals well below their individual no observable adverse effect levels (NOAELs), both with mixtures composed of similarly and dissimilarly acting agents. CONCLUSIONS: The widely held view that mixtures of dissimilarly acting chemicals are "safe" at levels below NOAELs is not supported by empirical evidence. We show that this view is also based on the erroneous assumption that NOAELs can be equated with zero-effect levels. Thus, on the basis of published evidence, it is difficult to rule out the possibility of mixture effects from low-dose multiple exposures. | ||||||||
| 6815 | 3.41 | 16239167 | 2005.12.30 | + | + | Rat epidermal keratinocyte organotypic culture (ROC) as a model for chemically induced skin irritation testing. | Toxicol Appl Pharmacol | |
| S Pappinen, S Pasonen-Seppänen, M Suhonen, R Tammi, A Urtti, | ||||||||
| The potential of rat epidermal keratinocyte (REK) organotypic culture (ROC) with proper stratum corneum barrier as a model for screening skin irritants was evaluated. The test chemicals were selected from ECETOC database (1995) and the observed in vitro irritation potential was compared to ECETOC in vivo primary irritation index (PII), to EU risk phrases, and to the harmonized OECD criteria. Chemicals were applied onto the stratum corneum surface of ROC for 30 min and samples were taken from the underlying medium at 4 and 8 h after exposure. Cell membrane integrity (determined by LDH assay) and pro-inflammatory effect (determined by IL-1alpha release) were verified at both time points and correlated to PII values. The best correlation (R(2) = 0.831) was seen with LDH leakage test. Based on obtained data, chemicals were classified according to criteria defined by EU and OECD. From 12 chemicals, only two were incorrectly classified according to OECD criteria when using LDH leakage and IL-1alpha release as irritation markers. At the end of experiment, chemical-treated ROC cultures were fixed and histological changes were assessed. Typical signs for irritation were lightly stained cytoplasm, condensed nuclei, cellular vacuolization, eosinophilic cytoplasms, and blebbing. These irritation effects of chemicals were graded visually into four classes (A-D). The extent of morphological perturbations of the cultures mostly correlated with PII. The present results indicate the validity of the ROC model in predicting skin irritation potential of chemicals and show that the use of set of irritation markers with different mechanistic responses gives more information on irritation than if only one marker was used. | ||||||||
| 6816 | 3.41 | 12908278 | 2003.09.26 | + | + | Functionalization of carbon nanotubes with bovine serum albumin in homogeneous aqueous solution. | J Nanosci Nanotechnol | |
| K Fu, W Huang, Y Lin, D Zhang, TW Hanks, AM Rao, YP Sun, | ||||||||
| Single-walled (SWNTs) and multiple-walled (MWNTs) carbon nanotubes were solubilized via the esterification of nanotube-bound carboxylic acids by oligomeric polyethylene glycol compounds. The water-soluble samples were used as starting materials in reactions with bovine serum albumin (BSA) protein in ambient aqueous solutions. The reaction conditions were designed for thermodynamically favorable transformation from ester to amide linkages, yielding SWNT-BSA and MWNT-BSA conjugates. The results show that the use of soluble starting nanotube materials in an indirect functionalization method represents a valuable approach to the biomodification of carbon nanotubes. | ||||||||
| 6817 | 3.41 | 15752045 | 2006.02.14 | + | + | Oligo(ethylene glycol) containing polymer brushes as bioselective surfaces. | Langmuir | |
| L Andruzzi, W Senaratne, A Hexemer, ED Sheets, B Ilic, EJ Kramer, B Baird, CK Ober, | ||||||||
| The nitroxide-mediated polymerization of styrenic monomers containing oligo(ethylene glycol) (OEGn) moieties was chosen for the preparation of biocompatible polymer brushes tethered to silicon oxide surfaces due to the broad range of monomer structures available and the use of a nonmetallic initiator. These surfaces were characterized by near-edge X-ray absorption fine structure and water contact angle measurements. The biocompatibility of these grown polymer brushes was studied and compared with deposited assemblies of surface-bound OEGn-terminated silanes with selected chain lengths. Grown polymer brushes with short OEGn side chains suppressed protein adsorption significantly more than the deposited assemblies of short OEGn chains, and this was attributed to higher surface coverage by the brushes. Cell adhesion studies confirmed that OEGn-containing polymer brushes are particularly effective in preventing nonspecific adhesion. Studies of protein adsorption and cell localization carried out with specific ligands on surfaces patterned demonstrated the potential of these surface-tethered polymer brushes for the formation of micro- and nanoscale devices. | ||||||||
| 6818 | 3.41 | 17266643 | 2008.04.11 | + | + | Neurotoxic prion protein (PrP) fragment 106-126 requires the N-terminal half of the hydrophobic region of PrP in the PrP-deficient neuronal cell line. | Protein Pept Lett | |
| A Sakudo, I Nakamura, DC Lee, K Saeki, K Ikuta, T Onodera, | ||||||||
| The cytotoxicity of aged PrP(106-126) was examined using an immortalized prion protein (PrP) gene-deficient neuronal cell line. The N-terminal half of the hydrophobic region (HR) but not the octapeptide repeat (OR) of PrP was required for aged PrP(106-126) neurotoxicity, suggesting that neurotoxic signals of aged PrP(106-126) are mediated by this region. | ||||||||
| 6819 | 3.41 | 11871550 | 2002.09.27 | + | + | Reactions of hydroxyl radical with humic substances: bleaching, mineralization, and production of bioavailable carbon substrates. | Environ Sci Technol | |
| JV Goldstone, MJ Pullin, S Bertilsson, BM Voelker, | ||||||||
| In this study, we examine the role of the hydroxyl (OH*) radical as a mechanism for the photodecomposition of chromophoric dissolved organic matter (CDOM) in sunlit surface waters. Using gamma-radiolysis of water, OH* was generated in solutions of standard humic substances in quantities comparable to those produced on time scales of days in sunlit surface waters. The second-order rate coefficients of OH* reaction with Suwannee River fulvic (SRFA; 2.7 x 10(4) s(-1) (mg of C/L)(-1)) and humic acids (SRHA; 1.9 x 10(4) s(-1) (mg of C/L)(-1)) are comparable to those observed for DOM in natural water samples and DOM isolates from other sources but decrease slightly with increasing OH* doses. OH* reactions with humic substances produced dissolved inorganic carbon (DIC) with a high efficiency of approximately 0.3 mol of CO2/mol of OH*. This efficiency stayed approximately constant from early phases of oxidation until complete mineralization of the DOM. Production rates of low molecular weight (LMW) acids including acetic, formic, malonic, and oxalic acids by reaction of SRFA and SRHA with OH* were measured using HPLC. Ratios of production rates of these acids to rates of DIC production for SRHA and for SRFA were similar to those observed upon photolysis of natural water samples. Bioassays indicated that OH* reactions with humic substances do not result in measurable formation of bioavailable carbon substrates other than the LMW acids. Bleaching of humic chromophores by OH* was relatively slow. Our results indicate that OH* reactions with humic substances are not likely to contribute significantly to observed rates of DOM photomineralization and LMW acid production in sunlit waters. They are also not likely to be a significant mechanism of photobleaching except in waters with very high OH* photoformation rates. | ||||||||
| 6820 | 3.41 | 17129015 | 2007.01.19 | + | + | Bipolar electrochemical mechanism for the propulsion of catalytic nanomotors in hydrogen peroxide solutions. | Langmuir | |
| Y Wang, RM Hernandez, DJ Bartlett, JM Bingham, TR Kline, A Sen, TE Mallouk, | ||||||||
| Bimetallic nanorods are propelled in aqueous solutions by the catalytic decomposition of hydrogen peroxide to oxygen and water. Several mechanisms (interfacial tension gradients, bubble recoil, viscous Brownian ratchet, self-electrophoresis) have been proposed for the transduction of chemical to mechanical energy in this system. From Tafel plots of anodic and cathodic hydrogen peroxide reactions at various metal (Au, Pt, Rh, Ni, Ru, and Pd) ultramicroelectrodes, we determine the potential at which the anodic and cathodic reaction rates are equal for each metal. These measurements allow one to predict the direction of motion of all possible bimetallic combinations according to the bipolar electrochemical (or self-electrophoretic) mechanism. These predictions are consistent with the observed direction of motion in all cases studied, providing strong support for the mechanism. We also find that segmented nanorods with one Au end and one poly(pyrrole) end containing catalase, an enzyme that decomposes hydrogen peroxide nonelectrochemically, perform the overall catalytic reaction at a rate similar to that of nanorods containing Au and Pt segments. However, in this case there is no observed axial movement, again supporting the bipolar electrochemical propulsion mechanism for bimetallic nanorods. | ||||||||
| 6821 | 3.41 | 8011862 | 1994.07.25 | + | + | Phase and structural changes in hydroxyapatite coatings under heat treatment. | Biomaterials | |
| Z Zyman, J Weng, X Liu, X Li, X Zhang, | ||||||||
| Hydroxyapatite (HA) crystallites of smaller size than those formed during the spraying process are found in HA coatings on titanium as a result of the crystallization of the amorphous phase (approximately 630 degrees C) when the coatings are vacuum-heat-treated in the temperature interval 100-1000 degrees C. As the annealing temperature increases within the 630-1000 degrees C range, the size of the crystallites increases, and at 1000 degrees C reaches the size of those formed during the process of spraying. At the same time, at 800 degrees C and above, HA transforms into other calcium phosphate phases (alpha-tricalcium phosphate, beta-tricalcium phosphate, tetracalcium monoxide diphosphate). These phase transformations lead to the increase of coating roughness. | ||||||||
| 6822 | 3.40 | 15467889 | 2005.10.04 | + | + | Synthesis and in vitro photodynamic activity of new hexadeca-carboxy phthalocyanines. | Chem Commun (Camb) | |
| CF Choi, PT Tsang, JD Huang, EY Chan, WH Ko, WP Fong, DK Ng, | ||||||||
| Two new hexadeca-carboxy phthalocyanines have been synthesised and evaluated for their photodynamic activities; the zinc(II) analogue exhibits a high class-A scavenger-receptor mediated photocytotoxicity towards the J774 murine macrophage cell line. | ||||||||
| 6823 | 3.40 | 16312812 | 2006.04.04 | + | Possible role of mitochondrial components in adriamycin-induced cytotoxicity of human leukemia cells. | J Chemother | ||
| LC Papadopoulou, C Wheeler, AS Tsiftsoglou, | ||||||||
| 6824 | 3.40 | 2398075 | 1990.10.12 | + | + | Study of the effect of the surface state on the cytocompatibility of a Co-Cr alloy using human osteoblasts and fibroblasts. | J Biomed Mater Res | |
| A Naji, MF Harmand, | ||||||||
| Cobalt-chromium-based alloys are widely used in oral and orthopedic implantology. Although they are relatively well tolerated, biological complications could occur which sometimes are due to the insufficient biocompatibility of the alloy. This study shows the effects of an alloy (Co (base), 28% Cr, 5.5% Mo, 1% Ni, 0.95% Si, 0.7% Fe, 0.65% Mn, 0.25% C), on differentiated human cells derived from an oral implantation site, specifically alveolar bone osteoblasts and gingival fibroblasts. The cytocompatibility of the alloy is determined by the study of cell proliferation, determination of total cell protein and intracellular alkaline phosphatase contents, cytoskeleton, and cell morphology. The alloy is presented to the cells in four different surface states: rough cast, specular polished, microbead blasted, and RF sputtered. The results demonstrate that the same material has different effects on the basal and specific cellular functions, according to its surface state. For this alloy we can classify its cytocompatibility according to its surface state in such an order: Microbead blasted much greater than specular polished greater than RF sputtered greater than rough cast. | ||||||||
| 6825 | 3.40 | 16550291 | 2007.03.22 | + | + | Luminescent nanobeads: attachment of surface reactive Eu(III) complexes to gold nanoparticles. | Chem Commun (Camb) | |
| DJ Lewis, TM Day, JV MacPherson, Z Pikramenou, | ||||||||
| Gold nanoparticles were used as a scaffold to assemble multiple tailor-made europium(III) complexes yielding water-soluble gold nanoparticles that display red, Eu(III), luminescence. | ||||||||
| 6826 | 3.40 | 15720139 | 2005.09.01 | + | + | From experiment to theory: molecular orbital parameters to interpret the skin sensitization potential of 5-chloro-2-methylisothiazol-3-one and 2-methylisothiazol-3-one. | Chem Res Toxicol | |
| AO Aptula, DW Roberts, MT Cronin, | ||||||||
| 5-Chloro-2-methylisothiazol-3-one (MCI) and 2-methylisothiazol-3-one (MI) are the major constituents of the commercial biocide Kathon CG. These two compounds have both been shown to exhibit skin sensitization potential: MCI is classified as an extreme sensitizer while MI is classified as a moderate sensitizer. The purpose of the present investigation was to provide further insights into the chemistry underlying their skin sensitizing properties. First, a molecular modeling (in silico) study was carried out of the initial reaction pathways of MI and MCI with nucleophiles representative of those involved in the skin sensitization process, and we compared the findings with the reported chemical and allergenic properties of these compounds. These reaction pathways were assessed using molecular orbital calculations. A novel parameter, the activation energy (AE) index, is proposed and is calculated from a knowledge of the energy changes in the frontier molecular orbitals as the electrophile is converted to an anionic intermediate. The AE indices correspond to the reactivity of MCI and MI with nucleophiles and also their skin sensitization potential. Second, the previously unexplained formation of final reaction products from MCI and butylamine is discussed and a reaction mechanism is proposed. A key finding of this analysis is that the reaction produces "positive chlorine" in the form of N-chloro- and/or N,N-dichloro-butylamine, which could contribute to the skin sensitizing properties of MCI. | ||||||||
| 6827 | 3.40 | 18463597 | 2008.07.18 | + | + | CuO and Ag2O/CuO catalyzed oxidation of aldehydes to the corresponding carboxylic acids by molecular oxygen. | Molecules | |
| Q Tian, D Shi, Y Sha, | ||||||||
| Furfural was oxidized to furoic acid by molecular oxygen under catalysis by 150 nm-sized Ag(2)O/CuO (92%) or simply CuO (86.6%). When 30 nm-size catalyst was used,the main product was a furfural Diels-Alder adduct. Detailed reaction conditions and regeneration of catalysts were investigated. Under optimal conditions, a series of aromatic and aliphatic aldehydes were oxidized to the corresponding acids in good yields. | ||||||||
| 6828 | 3.40 | 15205887 | 2005.04.11 | + | + | Subchronic inhalation toxicity of soluble hexavalent chromium trioxide in rats. | Arch Toxicol | |
| HY Kim, SB Lee, BS Jang, | ||||||||
| We performed a 90-day repeated-dose inhalation toxicity study of soluble hexavalent chromium trioxide (CrO3 (VI)). Male Sprague-Dawley (SD) rats were exposed to doses of CrO3 in the form of 0.5 approximately 5.0 microm aerosol at 0.00, 0.20, 0.50, and 1.25 mg/m3 for 6 h/day, 5 days/week for 13 weeks using inhalation chamber. CrO3 induced decrease of activity, alopecia and nasal hemorrhage. Body weights of the high-dose 1.25-mg/m3 exposure group were significantly lower than those of the control group. Hematological results revealed the reduction of the number of red blood cell and hematocrit values in the 1.25-mg/m3 exposure group. In addition, the hemoglobin values in the 0.50- and 1.25-mg/m3 exposure groups were significantly decreased compared with those of the control group. Clinical biochemical measurements revealed the reduction in total protein, albumin and alanine aminotransferase (ALT) level of the 0.50- and 1.25-mg/m3 exposure groups. Microscopic examination of the lung showed inflammation reactions caused by Cr exposure. In conclusion, the 13-week repeated exposure with soluble CrO3 demonstrated the injury in SD rats with the no observed adverse effect level (NOAEL) under 0.20 mg/m3. | ||||||||
| 6829 | 3.40 | 16574264 | 2006.07.06 | + | + | A low molecular weight fraction of polyethylenimine (PEI) displays increased transfection efficiency of DNA and siRNA in fresh or lyophilized complexes. | J Control Release | |
| S Werth, B Urban-Klein, L Dai, S Höbel, M Grzelinski, U Bakowsky, F Czubayko, A Aigner, | ||||||||
| RNA interference (RNAi) represents a powerful method for specific gene silencing. It is mediated through small double-stranded RNA molecules (small interfering RNAs, siRNAs) which sequence-specifically trigger the cleavage and subsequent degradation of their target mRNA. One critical factor that determines the success of RNAi is the ability to deliver intact siRNAs into target cells. Polyethylenimines (PEIs) are synthetic polymers with a high cationic charge density which function as transfection reagents based on their ability to compact DNA or RNA into complexes. This paper describes the application of lyophilized PEI/siRNA complexes based on a novel polyethylenimine. By fractionation of a commercially available 25-kDa PEI using gel permeation chromatography, a low molecular weight polyethylenimine (PEI F25-LMW) with superior transfection efficacy and low toxicity in various cell lines is obtained. Complexes formed in 5% glucose, but not in 150 mM NaCl, can be lyophilized and reconstituted without loss of transfection efficacy. Furthermore, PEI F25-LMW is able to complex and fully protect siRNAs against nucleolytic degradation, and delivers siRNAs into cells where they display bioactivity. Upon lyophilization and reconstitution of PEI F25-LMW-based siRNA complexes, siRNAs are still able to efficiently induce RNAi. To further demonstrate their applicability, lyophilized PEI/siRNA complexes are employed for targeting of the growth factor VEGF. Treatment of PC-3 prostate carcinoma cells with fresh or with lyophilized complexes results in decreased cell proliferation in different assays due to the siRNA-mediated downregulation of VEGF. In conclusion, siRNAs can be applied in lyophilized formulations, and lyophilized PEI F25-LMW-based siRNA complexes represent a powerful, inexpensive, non-toxic and simple ready-to-use platform for the specific and efficient targeting of genes in vitro. | ||||||||
| 6830 | 3.39 | 17914852 | 2008.01.09 | + | + | Direct observation of Brownian dynamics of hard colloidal nanorods. | Nano Lett | |
| H Maeda, Y Maeda, | ||||||||
| We synthesize monodisperse selenium (Se) colloidal rods, and the suspensions exhibit the smectic phase at a particle volume fraction (phi) of 0.28. Side-by-side rod clustering occurs at phi > 0.04. Cluster-size distributions and persistence times are determined for various phi. In dense suspensions (phi > 0.1), individual rods reveal characteristic fundamental motions, e.g., reptation and synchronized rotation. Mean-square displacements of the rods suggest a cage trapping and escape. Estimated translational and rotational diffusion coefficients show a large difference from predictions by computer simulations. | ||||||||
| 6831 | 3.39 | 18654253 | 2008.08.29 | Carbon does it again. | Nat Nanotechnol | |||
| 6832 | 3.39 | 14737310 | 2004.09.17 | + | + | Translocation of bioactive peptides across cell membranes by carbon nanotubes. | Chem Commun (Camb) | |
| D Pantarotto, JP Briand, M Prato, A Bianco, | ||||||||
| Functionalised carbon nanotubes are able to cross the cell membrane and to accumulate in the cytoplasm or reach the nucleus without being toxic for the cell up to 10 [micro sign]M. | ||||||||
| 6833 | 3.39 | 15002125 | 2004.09.20 | + | + | Si nanocolumns as novel nanostructured supports for enzyme immobilization. | J Nanosci Nanotechnol | |
| TJ Yim, DY Kim, SS Karajanagi, TM Lu, R Kane, JS Dordick, | ||||||||
| Silicon nanocolumns have been used as novel supports for the high-density immobilization of enzymes. Silicon nanocolumns with diameters of ca. 50-100 nm and a height of 1 micron were constructed using glancing angle deposition. The surfaces were successively treated with 3-aminopropyltriethoxysilane (APTES) and then with an amine reactive polymer, poly(ethylene-alt-maleic anhydride), to attach soybean peroxidase (SBP) to the support. Optimal coverage of APTES, polymer, and SBP was obtained for incorporation of enzyme onto the sidewalls of the nanocolumns. SBP immobilized on the silicon nanocolumns demonstrated an enhancement in biocatalytic activity of 160% over that of the enzyme immobilized on flat silicon wafers with the same projected area. The enzymatic activity decreased with progressive washes for both supports. This decrease in the activity of enzyme was found to be primarily due to the intrinsic deactivation of immobilized enzyme on the silicon surface. Designing nanocolumns with optimal dimensions, spacing, and surface chemistry may lead to the development of high-density arrays of proteins for applications in biotechnology. | ||||||||
| 6834 | 3.38 | 15909348 | 2005.10.18 | + | + | Preparation of high-permeability NiCuZn ferrite. | J Zhejiang Univ Sci B | |
| J Hu, M Yan, | ||||||||
| Appropriate addition of CuO/V2O5 and the reduction of the granularity of the raw materials particle decrease the sintering temperature of NiZn ferrite from 1200 degrees C to 930 degrees C. Furthermore, the magnetic properties of the NiZn ferrite prepared at low temperature of 930 degrees C is superior to that of the NiZn ferrite prepared by sintering at high temperature of 1200 degrees C because the microstructure of the NiZn ferrite sintered at 930 degrees C is more uniform and compact than that of the NiZn ferrite sintered at 1200 degrees C. The high permeability of 1700 and relative loss coefficient tandelta/mu(i) of 9.0x10(-6) at 100 kHz was achieved in the (Ni0.17Zn0.63Cu0.20)Fe1.915O4 ferrite. | ||||||||
| 6835 | 3.37 | 12775051 | 2003.10.06 | + | + | Mechanisms affecting the infiltration and distribution of ethanol-blended gasoline in the vadose zone. | Environ Sci Technol | |
| CJ McDowell, SE Powers, | ||||||||
| One- and two-dimensional experiments were conducted to examine differences in the behavior of gasoline and gasohol (10% ethanol by volume) as they infiltrate through the unsaturated zone and spread at the capillary fringe. Ethanol in the spilled gasohol quickly partitions into the residual water in the vadose zone and is retained there as the gasoline continues to infiltrate. Under the conditions tested, over 99% of the ethanol was initially retained in the vadose zone. Depending on the volume of gasoline spilled and the depth to the water table, this causes an increase in the aqueous-phase saturation and relative permeability, thus allowing the ethanol-laden water to drain into the gasoline pool. Under the conditions tested, the presence of ethanol does not have a significant impact on the overall size or shape of the resulting gasoline pool at the capillary fringe. Residual gasoline saturations in the vadose zone were significantly reduced however because of reduced surface and interfacial tensions associated with high ethanol concentrations. The flux of ethanol in the effluent of the column ranged from 1.4 x 10(-4) to 4.5 x 10(-7) g/(cm2 min) with the LNAPL and from 6 x 10(-3) to 3.0 x 10(-4) g/(cm2 min) after water was introduced to simulate rain infiltration. The experimental results presented here illustrate that the dynamic effects of ethanol partitioning into the aqueous phase in the vadose zone create an initial condition that is significantly different than previously understood. | ||||||||
| 6836 | 3.37 | 17328164 | 2007.04.05 | + | Nanomaterials meet increased scrutiny. | Environ Sci Technol | ||
| K Christen, | ||||||||
| 6837 | 3.37 | 15986678 | 2006.05.03 | + | + | In situ photopolymerization of a polymerizable poly(ethylene glycol)-covered phospholipid monolayer on a methacryloyl-terminated substrate. | Langmuir | |
| K Kim, K Shin, H Kim, C Kim, Y Byun, | ||||||||
| We have prepared a chemically anchored monolayer of PEG (poly(ethylene glycol)) and phospholipid mixture (PEG/phospholipid) on a methacryloyl-terminated substrate by in situ photopolymerization. Both monoacryloyl phospholipid (acryloyl-PC, 1-palmitoyl-2-[12-(acryloyloxy)dodecanoyl]-sn-glycero-3-phosphocholine) and monoacryloyl PEG (acryloyl-PEG, 12-(acryloyloxy)dodecanoyl-PEG) were synthesized by modifyingphospholipid and PEGwith 12-(acryloyloxy)-1-dodecanoic acid and 12-(acryloyloxy)-1-dodecanol, respectively. The surface pressure-area (pi-A) isotherm showed that acryloyl-PEG molecules were stable in the phospholipid monolayer and that they could be evenly inserted into a phospholipid monolayer at the air/water interface. By adding 10 mol % acryloyl-PEG into phosholipid vesicles, we could produce a PEG/phosholipid monolayer on methacryloyl-terminated substrates using vesicle fusion for 3 h. Then, this polymerizable PEG/phospholipid monolayer was in situ photopolymerized onto a methacryloyl-terminated substrate with eosin Y/triethanolamine as co-initiators. Optimal vesicle fusion and irradiation condition were determined with respect to the vesicle fusion time and duration of irradiation. As confirmed by atomic force microscopy and X-ray reflectivity studies, the polymerized PEG/phosholipid surface formed a PEG-covered phospholipid monolayer with thicknesses of 3 and 6 nm for the base phospholipid monolayer and the covering PEG layer, respectively. The chemical anchoring efficiency ofpolymerized PEG and phospholipid molecules, which was calculated by the relative carbon ratio of each surface before and after methanol washing using X-ray photoelectron spectroscopy, was 98%. This polymerized PEG/phosholipid monolayer showed good stability in organic solution due to firm chemical anchoring to a solid surface. | ||||||||
| 6838 | 3.37 | 12914069 | 2003.09.16 | + | + | Morphology and current-voltage characteristics of nanostructured pentacene thin films probed by atomic force microscopy. | J Nanosci Nanotechnol | |
| S Zorba, QT Le, NJ Watkins, L Yan, Y Gao, | ||||||||
| Atomic force microscopy was used to study the growth modes (on SiO2, MoS2, and Au substrates) and the current-voltage (I-V) characteristics of organic semiconductor pentacene. Pentacene films grow on SiO2 substrate in a layer-by-layer manner with full coverage at an average thickness of 20 A and have the highest degree of molecular ordering with large dendritic grains among the pentacene films deposited on the three different substrates. Films grown on MoS2 substrate reveal two different growth modes, snowflake-like growth and granular growth, both of which seem to compete with each other. On the other hand, films deposited on Au substrate show granular structure for thinner coverages (no crystal structure) and dendritic growth for higher coverages (crystal structure). I-V measurements were performed with a platinum tip on a pentacene film deposited on a Au substrate. The I-V curves on pentacene film reveal symmetric tunneling type character. The field dependence of the current indicates that the main transport mechanism at high field intensities is hopping (Poole-Frenkel effect). From these measurements, we have estimated a field lowering coefficient of 9.77 x 10(-6) V-1/2 m1/2 and an ideality factor of 18 for pentacene. | ||||||||
| 6839 | 3.37 | 15336890 | 2005.03.22 | + | + | Degradation of pentachlorophenol in cyclodextrin extraction effluent using a photocatalytic process. | Sci Total Environ | |
| K Hanna, Ch de Brauer, P Germain, JM Chovelon, C Ferronato, | ||||||||
| This work evaluates a process for the elimination of pentachlorophenol (PCP) from effluents provided by a cyclodextrin-assisted flushing of contaminated soils. The effectiveness of photocatalytic degradation of PCP in several cyclodextrin (CD) solutions was evaluated using TiO2 as a photocatalyst. Effects of CD type on PCP degradation rate were studied at two pH values. A similar effect was observed for all CDs used on degradation rate of PCP and the decay of PCP was found to be less extensive at pH 11 than at pH 7. The kinetic orders of the photocatalytic reactions of PCP for all of the solutions have been determined. The first-order rate constants were found to be 0.0884, 0.0362, 0.0197 and 0.0053 min(-1) in CD solutions, respectively, at 0, 1, 2 and 5 mmol l(-1) of CD. Batch experiments were performed in order to study the CD extraction enhancement of PCP previously adsorbed on soil. The results show that the removal capacity of PCP from soil increases with CD concentration (from 0 to 5 mmol l(-1)). When the CD concentration was 5 mmol l(-1), an extraction of about 70% of PCP adsorbed on soil was observed, whereas only 37% was removed when water was used as the flushing solution. The optimal conditions for such a coupled method depend on the nature and concentration of the extracting agent and also on the photocatalytic experimental conditions. This work revealed that the coupling of cyclodextrin-enhanced solubilization and photocatalytic treatment is a promising method for contaminated soil remediation. | ||||||||
| 6840 | 3.37 | 12765247 | 2003.06.10 | + | + | The effect of m-xylene on cytotoxicity and cellular antioxidant status in rat dermal equivalents. | Toxicol Lett | |
| CA Coleman, BE Hull, JN McDougal, JV Rogers, | ||||||||
| Exposure of the skin to volatile organic chemicals (VOCs) can lead to irritation, inflammation and cytotoxicity. Since VOCs are used in industrial, commercial and military applications, concern is mounting with respect to VOC safe exposure limits. Although traditional toxicological assessment of VOCs has utilized animal models, the use of alternative in vitro models is becoming more widespread. We have previously developed a sealed exposure system that prevents chemical loss through evaporation and enables calculation of target cell chemical dose. The present study utilized this in vitro exposure method to assess m-xylene-induced cytotoxicity and antioxidant status in dermal equivalents (dermal fibroblasts in a collagen matrix). At the end of a 1- or 4-h exposure, cytotoxicity was measured using the MTT assay and the EC50 values determined were 1481 +/- 88 and 930 +/- 33, respectively. Decreases in cellular thiols and catalase activity were observed, which occurred in a time and dose-dependent manner. Treatment of dermal equivalents with the antioxidants N-acetylcysteine (NAC) and catalase provided some protection against m-xylene-induced cytotoxicity. When compared to m-xylene exposures, treatment with either 1.0 or 5.0 mM NAC led to increases in the EC50 values at 1 and 4 h. Increases in these EC50 values ranged from 1.22- to 1.32-fold at 1 h and 1.27- to 1.54-fold at 4 h. Although treatment with catalase (1000 U/ml) led to a 1.35-fold increase in cell viability at 1 h, no significant differences were observed at either 1 or 4 h when compared to dermal equivalents exposed to m-xylene alone. These results suggest that exposure to m-xylene leads to a time- and dose-dependent decrease in cellular antioxidants and that cellular thiols may provide protection against the cytotoxic properties of m-xylene. | ||||||||
| 6841 | 3.37 | 17317054 | 2007.07.19 | + | + | Elaboration of PLLA-based superparamagnetic nanoparticles: characterization, magnetic behaviour study and in vitro relaxivity evaluation. | Int J Pharm | |
| M Hamoudeh, A Al Faraj, E Canet-Soulas, F Bessueille, D Léonard, H Fessi, | ||||||||
| Oleic acid-coated magnetite has been encapsulated in biocompatible magnetic nanoparticles (MNP) by a simple emulsion evaporation method. The different parameters influencing the particles size were studied. Between these parameters, the stirring speed and the polymer concentration were found to influence positively or negatively, respectively, the MNP size which varied between 320 and 1500nm. The magnetite encapsulation efficacy was about than 90% yielding a high magnetite loading of up to 30% (w/w). X-ray diffraction showed that magnetite crystalline pattern was not modified after emulsification and solvent evaporation. The X-ray photoelectron spectroscopy (XPS) results indicated the presence of less than 0.1% of iron atoms at the nanoparticles surface. Vibration simple magnetometer (VSM) showed a superparamagnetic behaviour of the MNP and a saturation magnetization increasing with the increased magnetite amount used in formulation. Moreover, T(1) and T(2) relaxivities of MNP (4.7T, 20 degrees C) were 1.7+/-0.1 and 228.3+/-13.1s(-1)mM(-1), respectively, rendering them in the same category of known negative contrast agents which shorten the T(2) relaxation time. Therefore, by using an appropriate anticancer drug in their formulation, these magnetic nanoparticles can present a promising mean for simultaneous tumor imaging, drug delivery and real time monitoring of therapeutic effect. | ||||||||
| 6842 | 3.36 | 15820899 | 2005.09.08 | + | + | Raman study of TiO2 role in SiO2-Al2O3-MgO-TiO2-ZnO glass crystallization. | Spectrochim Acta A Mol Biomol Spectrosc | |
| K Furić, L Stoch, J Dutkiewicz, | ||||||||
| Tough glass-ceramic material of special mechanical properties with nanosize crystal phases formed by appropriately controlled crystallization was studied by Raman spectroscopy. It was obtained by TiO2 activated crystallization of Mg-aluminosilicate glass of SiO2-Al2O3-MgO-TiO2-ZnO composition. Crystallization was preceded by a change in the TiO2 structural position and state, which is manifested by a changed color of glass from yellow into blue shortly before the glass transformation (Tg) temperature. Raman spectroscopy was applied to explain the mechanism of this process and to establish the role of TiO2 in the early stage of glass crystallization that precedes a complete crystal phase formation. The starting glasses were found in almost complete disorder, since all bands were weak, broad and dominated by a Bose band at about 90 cm-1. After the sample annealing all bands turned out better resolved and the Bose band practically disappeared, both confirming the amorphous structure reorganization process. A multiplet observed in the vicinity of 150 cm-1 we assigned to the anatase and other titania structures that can be considered prime centers of crystallization. Finally, in the closest neighborhood of the Rayleigh line the low frequency mode characterizing nanoparticles was observed. According to this band theory, the mean size of initial titania crystallites is about 10nm for all samples, but the size distribution varies within factor two among them. | ||||||||
| 6843 | 3.36 | 16529419 | 2006.07.21 | + | + | Phosphorylcholine-based pH-responsive diblock copolymer micelles as drug delivery vehicles: light scattering, electron microscopy, and fluorescence experiments. | Biomacromolecules | |
| C Giacomelli, L Le Men, R Borsali, J Lai-Kee-Him, A Brisson, SP Armes, AL Lewis, | ||||||||
| The micellization behavior of a diblock copolymer comprising a highly hydrophilic and biocompatible poly(2-methacryloyloxyethyl phosphorylcholine) (PMPC) corona-forming block and a pH-sensitive poly(2-(diisopropylamino)ethyl methacrylate) (PDPA) core-forming block (PMPC-b-PDPA) has been studied by static and dynamic light scattering (SDLS), transmission electron microscopy (TEM), and potentiometry. Self-assembly of PMPC-b-PDPA copolymers with two different DPA volume fractions (phi(DPA)) leads to narrowly distributed and structurally distinct spherical micelles, as evidenced by their molecular weight (M(w,mic)), aggregation number (N(agg)), hydrodynamic radius (R(H)), corona width (W), and core radius (R(c)). The excellent potential of these pH-responsive micelles as nanosized drug delivery vehicles was illustrated by the encapsulation of dipyridamole (DIP), a model hydrophobic drug that dissolves in acid solutions and becomes insoluble above pH 5.8, which is comparable to the pK(a) of the PDPA block. The influence of micelle structure (namely M(w,mic), N(agg), R(H), W, and R(c)) on drug loading content, drug loading efficiency, partition coefficient, and release kinetics was investigated and confirmed by fluorescence spectroscopy studies. The maximum dipyridamole loadings within PMPC(30)-b-PDPA(30) (R(H) = 14.0 nm; W = 4.8 nm; R(c) = 9.2 nm) and PMPC(30)-b-PDPA(60) (R(H) = 27.1 nm; W = 11.0 nm; R(c) = 16.1 nm) micelles were 7 and 12% w/w(p), respectively. This preferential solubilization of DIP into micelles formed by copolymer chains having longer core-forming blocks (i.e., possessing larger core volumes) reflects the larger partition coefficient (K(V)) of DIP between the aqueous phase and PMPC(30)-b-PDPA(60) micelles (K(V) = 5.7 x 10(4)) compared to PMPC(30)-b-PDPA(30) micelles (K(V) = 1.1 x 10(4)). This enhanced ability of PMPC(30)-b-PDPA(60) aggregates to entrap/stabilize small hydrophobic molecules also produces slower release kinetics. Rapid release can be triggered by lowering the pH to induce micellar dissociation. | ||||||||
| 6844 | 3.36 | 15530050 | 2005.04.01 | + | + | Synthesis of chitosan-stabilized gold nanoparticles in the absence/presence of tripolyphosphate. | Biomacromolecules | |
| H Huang, X Yang, | ||||||||
| Gold nanoparticles were prepared by reducing gold salt with a polysaccharide, chitosan, in the absence/presence of tripolyphosphate (TPP). Here, chitosan acted as a reducing/stabilizing agent. The obtained gold nanoparticles were characterized with UV--vis spectroscopy and transmission electron microscopy. The results indicated that the shape and size distribution of gold nanoparticles changed with the molecular weight and concentration of chitosan. More interestingly, the gelation of chitosan upon contacting with polyanion (TPP) can also affect the shape and size distribution of gold nanoparticles. By adding TPP to chitosan solution before the reduction of gold salt, gold nanoparticles have a bimodal size distribution, and at the same time, polygonal gold particles were obtained in addition to spherical gold nanoparticles. | ||||||||
| 6845 | 3.36 | 18019128 | 2007.12.27 | + | + | Synthesis of polymer stabilized silver and gold nanostructures. | J Nanosci Nanotechnol | |
| SK Bajpai, YM Mohan, M Bajpai, R Tankhiwale, V Thomas, | ||||||||
| This review article is focused on the various approaches that have been made to synthesize metal nanoparticles with predetermined shape, size, and fair stability. Due emphasis has been given on polymer stabilized nanoparticles. In addition use of other varieties of stabilizers like inorganic salts, organic compounds, organic solvent, biological molecules, etc. have also been discussed. Finally, formation of two and three-dimensional nanostructures like nanowires, nanodiscs, nanoprisms has also been revealed. | ||||||||
| 6846 | 3.36 | 1446000 | 1992.12.29 | + | + | A study of inactivation reactions of N-acetylcysteine with mucochloric acid, a mutagenic product of the chlorination of humic substances in water. | Chem Res Toxicol | |
| RT LaLonde, S Xie, | ||||||||
| The Salmonella typhimurium (TA100) mutagenic compound, mucochloric acid [3,4-dichloro-5-hydroxy-2(5H)-furanone (MCA)], was inactivated by in vitro N-acetylcysteine (NAC). The reaction of MCA with NAC at pH7 was second order and gave products 4, 5, and 6a that resulted from the displacement of chlorine from C-3 or C-4 of MCA. The sodium borohydride treatment of product 4 gave the same product (7) as was obtained by treating 3,4-dichloro-2(5H)-furanone with NAC. The treatment of MCA with (R)-(+)-cysteine gave the bicyclic product 9a, in which the two chlorine atoms of MCA were still present. This product was slightly more mutagenic than MCA, whereas product 5 was less mutagenic than MCA and product 4 was nonmutagenic in the Salmonella typhimurium (TA100) assay. | ||||||||
| 6847 | 3.36 | 14744789 | 2004.04.02 | + | + | Determination and modeling of kinetics of cancer cell killing by doxorubicin and doxorubicin encapsulated in targeted liposomes. | Cancer Res | |
| RE Eliaz, S Nir, C Marty, FC Szoka, | ||||||||
| Various mathematical approaches have been devised to relate the cytotoxic effect of drugs in cell culture to the drug concentration added to the cell culture medium. Such approaches can satisfactorily account for drug response when the drugs are free in solution, but the approach becomes problematic when the drug is delivered in a drug delivery system, such as a liposome. To address this problem, we have developed a simple model that assumes that the cytotoxic potency of a drug is a function of the intracellular drug level in a critical compartment. Upon exposure to drug, cell death commences after a lag time, and the cell kill rate is dependent on the amount of drug in the critical intracellular compartment. The computed number of cells in culture, at any time after exposure to the drug, takes into account the cell proliferation rate, the cell kill rate, the average intracellular drug concentration, and a lag time for cell killing. We have applied this model to compare the cytotoxic effect of doxorubicin (DOX), or DOX encapsulated in a liposome that is targeted to CD44 on B16F10 melanoma cells in culture. CD44 is the surface receptor that binds to hyaluronan and is overexpressed on various cancer cells, including B16F10. We have shown previously that the drug encapsulated in hyaluronan-targeted liposomes was more potent than was the free drug. The model required the determination of the cell-associated DOX after the cells were incubated with various concentrations of the free or the encapsulated drug for 3 h, and the quantification of cell number at various times after exposure to the drug. The uptake of encapsulated drug was greater than that of the free drug, and the ratio of cell association of encapsulated:free drug was 1.3 at 0.5 micro g/ml and increased to 3.3 at 20 micro g/ml DOX. The results demonstrate that the enhanced potency of the encapsulated drug could stem from its enhanced uptake. However, in certain cases, where larger amounts of the free drug were added, such that the intracellular amounts of drug exceeded those obtained from the encapsulated drug, the numbers of viable cells were still significantly smaller for the encapsulated drug. This finding demonstrates that for given amounts of intracellular DOX, the encapsulated form was more efficient in killing B16F10 cells than the free drug. The outcome was expressed in the kinetic model as a 5-6-fold larger rate constant of cell killing potency for the encapsulated drug versus the free drug. The model provides a quantitative framework for comparing the cytotoxic effect in cultured cells when applying the drug in the free form or in a delivery system. | ||||||||
| 6848 | 3.36 | 15158964 | 2004.10.05 | + | + | Devices based on intelligent biopolymers for oral protein delivery. | Int J Pharm | |
| NA Peppas, | ||||||||
| The primary goal of bioadhesive controlled drug delivery is to localize a delivery device within the body to enhance the drug absorption process in a site-specific manner. An important contributor to good adhesion is the presence of molecular adhesion promoters such as polymer-tethered structure (e.g., poly(ethylene glycol) chains grafted to crosslinked networks) or even linear chains which are free to diffuse across the gel/gel interface. Recently, we have developed a very promising class of carriers for drug and especially protein delivery. Copolymer networks of poly(methacrylic acid) grafted with poly(ethylene glycol) exhibit reversible, pH-dependent swelling behavior due to the formation of interpolymer complexes between protonated pendant acid groups and the etheric groups on the graft chains. Gels containing equimolar amounts of MAA/EG exhibited the lowest degree of swelling at low pH increased complexation. The average network mesh size or correlation length was dramatically affected by the pH of the swelling solution. The in vitro release of insulin from P(MAA-g-EG) gels containing PEG grafts of molecular weight 1000 indicates a significant release of insulin as the gel decomplexes and insulin is freed through the structure. The results of additional in vitro studies have shown that insulin release rates can be controlled by appropriate adjustment of the structure of the gels. | ||||||||
| 6849 | 3.36 | 18686779 | 2008.09.16 | + | + | Targeted gadolinium-loaded dendrimer nanoparticles for tumor-specific magnetic resonance contrast enhancement. | Int J Nanomedicine | |
| SD Swanson, JF Kukowska-Latallo, AK Patri, C Chen, S Ge, Z Cao, A Kotlyar, AT East, JR Baker, | ||||||||
| A target-specific MRI contrast agent for tumor cells expressing high affinity folate receptor was synthesized using generation five (G5) ofpolyamidoamine (PAMAM) dendrimer. Surface modified dendrimer was functionalized for targeting with folic acid (FA) and the remaining terminal primary amines of the dendrimer were conjugated with the bifunctional NCS-DOTA chelator that forms stable complexes with gadolinium (Gd III). Dendrimer-DOTA conjugates were then complexed with GdCl3 followed by ICP-OES as well as MRI measurement of their longitudinal relaxivity (T1 s(-1) mM(-1)) of water. In xenograft tumors established in immunodeficient (SCID) mice with KB human epithelial cancer cells expressing folate receptor (FAR), the 3D MRI results showed specific and statistically significant signal enhancement in tumors generated with targeted Gd(III)-DOTA-G5-FA compared with signal generated by non-targeted Gd(III)-DOTA-G5 contrast nanoparticle. The targeted dendrimer contrast nanoparticles infiltrated tumor and were retained in tumor cells up to 48 hours post-injection of targeted contrast nanoparticle. The presence of folic acid on the dendrimer resulted in specific delivery of the nanoparticle to tissues and xenograft tumor cells expressing folate receptor in vivo. We present the specificity of the dendrimer nanoparticles for targeted cancer imaging with the prolonged clearance time compared with the current clinically approved gadodiamide (Omniscan) contrast agent. Potential application of this approach may include determination of the folate receptor status of tumors and monitoring of drug therapy. | ||||||||
| 6850 | 3.36 | 17584897 | 2008.06.02 | + | + | Bioactivity and cytocompatibility of silicon wafers treated by water. | J Biomed Mater Res A | |
| Y Niu, X Liu, C Ding, | ||||||||
| A range of bioactive ceramics can induce bone-like apatite to deposit on their surface in simulated body fluid (SBF). In this work, the silicon wafer was treated using deionized water to improve its bioactivity. The morphology and chemical composition of the treated silicon wafer was examined using Fourier transform infrared spectroscopy, atomic force microscopy and X-ray photoelectron spectroscopy. Field emission scanning electron microscopy was used to observe the surface morphologies of silicon wafers soaked in SBF. The results indicated that a hydrated sub-oxide film having Si--OH groups formed on the surface of the silicon wafer after the water treatment. The amount of Si--OH groups increased with raising the treatment temperature or prolonging the immersion time. Apatite was deposited on the surface of water-treated silicon wafers immersed in SBF. The apatite deposition was correlated with the amount of Si--OH groups. Human mesenchymal stem cells cultured on the surface of the water-treated silicon wafers showed good adhesion and spread, indicating that the cytocompatibility of silicon wafer was enhanced by this water treatment. | ||||||||
| 6851 | 3.36 | 17073500 | 2007.09.07 | + | + | Effect of hydrophobicity inside PEO-PPO-PEO block copolymer micelles on the stabilization of gold nanoparticles: experiments. | Langmuir | |
| S Chen, C Guo, GH Hu, J Wang, JH Ma, XF Liang, L Zheng, HZ Liu, | ||||||||
| In this paper we present the effect of poly(ethylene oxide)-poly(propylene oxide)-poly(ethylene oxide) block copolymer micelles and their hydrophobicity on the stabilization of gold nanoparticles. Gold nanoparticles were prepared by a method developed by Sakai et al. (Sakai, T.; Alexandridis, P. Langmuir 2004, 20, 8426). An absorption centered at 300-400 nm in time-dependent UV spectra provided evidence that the very first step of the synthesis was to form primary gold clusters. Then the gold clusters grew in size and were stabilized by block copolymer micelles. The stabilization capacities of the micelles were modulated by tuning the block copolymer concentration and composition and by adding salts. With good stabilization, gold particles were spherical and uniform in size with a diameter of 5-10 nm. Otherwise they were aggregates with irregular shapes such as triangular, hexagonal, and rodlike. The presence of a small amount of NaF significantly increased the stabilization capacity of the micelles and consequently modified the quality of the gold particles. Using FTIR and 1H NMR spectroscopy, micellization of the block copolymers and hydrophobicity of the micelles were proven very important for the stabilization. A higher hydrophobicity of the micelle cores was expected to favor the entrapment of primary gold clusters and the stabilization of gold nanoparticles. | ||||||||
| 6852 | 3.36 | 18403781 | 2008.09.10 | + | + | Identification of transforming growth factor beta1-driven genetic programs of acute lung fibrosis. | Am J Respir Cell Mol Biol | |
| AM Pulichino, IM Wang, A Caron, J Mortimer, A Auger, Y Boie, JA Elias, A Kartono, L Xu, J Menetski, CE Sayegh, | ||||||||
| Lung fibrosis is characterized by excessive accumulation of extracellular matrix components leading to progressive airflow limitation. Distinct profibrotic pathways converge on the activation of transforming growth factor-beta (TGF-beta), a central growth factor implicated in most fibroproliferative diseases. Recently, enforced expression of bioactive human TGF-beta1 (hTGF-beta1) in lungs of transgenic mice was shown to recapitulate several key pathophysiologies observed in fibrotic disorders of the lung, including cellular inflammation, tissue fibrosis, and myofibroblast hyperplasia. Inducible expression of hTGF-beta1 in this system provided a unique opportunity to characterize TGF-beta-driven mechanisms that precede and/or follow the onset of inflammation and fibrosis. Using gene expression profiling in lungs, we demonstrate temporal activation of key genetic programs regulating cell movement and invasiveness, inflammation, organ remodeling, and fibrosis. Consistent with our gene expression data, multiple soluble mediators associated with inflammation and tissue remodeling were markedly elevated in the bronchoalveolar lavage fluid of mice expressing hTGF-beta1. We observe significant TGF-beta1-driven infiltration of F4/80+ mononuclear cells producing bioactive arginase, a marker of alternatively activated macrophages. Finally, we identified a common "fibrosis" gene signature when comparing our findings with published data derived from preclinical and clinical studies. | ||||||||
| 6853 | 3.36 | 11055343 | 2001.02.22 | + | + | (E) -6-(1-alkyloxyiminoalkyl)-5,8-dimethoxy-1,4-naphthoquinones: synthesis, cytotoxic activity and antitumor activity. | Bioorg Med Chem Lett | |
| YJ You, Y Kim, GY Song, BZ Ahn, | ||||||||
| All of 13 (E)-6-(1-alkyloxyiminomethyl)-5,8-dimethoxy-1,4-naphthoquinone derivatives synthesized showed high ED50 values, ranging from 0.1 to 0.3 microg/mL against L1210 cells. However, they were inactive on A549 cells. Nine compounds exhibited higher T/C (%) values (318-388%) than Adriamycin (T/C, 315%). | ||||||||
| 6854 | 3.36 | 14503406 | 2004.04.30 | + | + | Magnetic properties of iron nitride-silica nanocomposite materials prepared by high-energy ball milling. | J Nanosci Nanotechnol | |
| SR Mishra, A Viano, S Roy, N Ali, J Losby, | ||||||||
| Powder mixtures of (FexN)y and (SiO2)1-y, with x between 3 and 4 and y equal to 0.2 or 0.6, were ball-milled for 4, 8, 16, 32, and 64 h. X-ray diffraction, thermal analysis, and magnetization measurements allowed an investigation of structural and magnetic properties to be carried out. The samples consist of nanostructured Fe3N and Fe4N particles in a SiO2 matrix. As the milling time increases, the Fe4N phase is eliminated from the particles in favor of Fe3N. Coercive fields as high as 270 and 84 Oe are obtained for (FexN)0.2(SiO2)0.8 at 5 and 300 K, respectively. This higher coercive field, upon cooling, indicates the presence of small superparamagnetic particles. The coercive field also increases with milling time, which is due to the reduced particle size and induced stain. The saturation magnetization decreases with increased milling time as a consequence of an increase in the superparamagnetic fraction and increased strain. Hard and soft magnetic properties are observed for y = 0.2 and y = 0.6 samples, respectively. | ||||||||
| 6855 | 3.35 | 17718531 | 2007.11.13 | + | + | Direct observation of plasmonic modes in au nanowires using high-resolution cathodoluminescence spectroscopy. | Nano Lett | |
| EJ Vesseur, R de Waele, M Kuttge, A Polman, | ||||||||
| We use cathodoluminescence imaging spectroscopy to excite and investigate plasmonic eigenmodes of Au nanowires with lengths of 500-1200 nm and approximately 100 nm width. We observe emission patterns along the Au nanowire axis that are symmetric and strongly wavelength dependent. Different patterns correspond to different resonant modes of the nanowire. From the observed patterns, we derive the spatial and spectral properties of the wire eigenmodes and determine the dispersion relation for plasmonic Au nanowire modes. | ||||||||
| 6856 | 3.35 | 16834997 | 2007.08.28 | + | + | Genotoxicant accumulation and cellular defence activation in bivalves chronically exposed to waterborne contaminants from the Seine River. | Aquat Toxicol | |
| B Rocher, J Le Goff, L Peluhet, M Briand, H Manduzio, J Gallois, MH Devier, O Geffard, L Gricourt, S Augagneur, H Budzinski, D Pottier, V André, P Lebailly, J Cachot, | ||||||||
| The aim of the present work was to investigate genotoxicant accumulation and biological responses of zebra mussels and blue mussels collected along a pollution gradient in the Seine estuary and in the Seine Bay. The sampling area included three contaminated and one reference sites for each species. The study focused on polyaromatic hydrocarbons (PAH), lindane, polychlorobiphenyls (PCB) and metals known to be potential genotoxicants and/or reactive oxygen species (ROS) inducers. Enzymatic activities related to cellular defence systems including the phase II enzyme glutathione S-transferase (GST) and three antioxidant enzymes superoxide dismutase (SOD), catalase (CAT) and glutathione peroxidase (GPx) were measured in gills. DNA adducts and DNA strand breaks (Comet assay) were measured in digestive gland and hemocytes, respectively. Species differences were observed in metal accumulation (As and Pb), GPx activity and DNA adduct formation. A marked upstream-downstream gradient was reported for PAH body burden and to a lesser extent for PCB and metals with the highest values measured just downstream the industrialized area of Rouen. GST and SOD activities in gills of bivalves were positively related to PAH and metals body burden, respectively. Activation of those cellular defences may prevent accumulation of electrophilic metabolites and free radicals and thus may protect DNA and others macromolecules against oxidation and adduction. Although DNA strand breaks and bulky adducts were detected in both species, levels were relatively low and no significant site differences were observed in June 2003. Our results indicate a clear relationship between genotoxicant accumulation and positive activation of detoxification and antioxidant systems but poor consequences in term of DNA damage for wild population of mussels inhabiting the Seine estuary. | ||||||||
| 6857 | 3.35 | 18468072 | 2008.06.03 | + | + | Experimental design and multivariate analysis for optimizing poly(D,L-lactide-co-glycolide) (PLGA) nanoparticle synthesis using molecular micelles. | J Nanosci Nanotechnol | |
| GM Ganea, CM Sabliov, AO Ishola, SO Fakayode, IM Warner, | ||||||||
| The utility of polymeric nanoparticles as drug delivery systems depends on effective control of synthetic parameters with a significant impact on their physico-chemical characteristics. In this study, a chemometric central composite experimental design (CCD) was used to optimize the synthesis of poly(D,L-lactide-co-glycolide) (PLGA) nanoparticles by emulsification solvent evaporation using anionic molecular micelles, such as poly(sodium N-undecylenic sulfate) (poly-SUS), poly(sodium N-undecanoyl-glycinate) (poly-SUG) and poly(sodium N-undecanoyl-L-leucyl-valinate) (poly-L-SULV) as well as conventional emulsifiers, such as anionic sodium dodecyl sulfate (SDS) and non-ionic poly(vinyl alcohol) (PVA). The individual and combined effects of PLGA concentration, emulsifier concentration, homogenization speed, and sonication time (design variables) on particle size and polydispersity index (responses) were investigated using multivariate analysis. The most significant design variables influencing the nanoparticle size and size distribution were PLGA concentration and emulsifier concentration (p < 0.05) in comparison to the other design variables. The quadratic model demonstrated the highest predictive ability when the molecular micelles were used as emulsifiers. The PLGA nanoparticles optimally synthesized according to the CCD were further purified by dialysis and then freeze-dried. Dried nanoparticles synthesized with molecular micelles and PVA were readily re-suspended in water, as compared with SDS for which nanoparticle aggregation occurred. The size of PLGA nanoparticles synthesized using molecular micelles increased after freeze-drying, but remained smaller than 100 nm when poly-L-SULV was used as emulsifier. The PDI values indicated monodisperse nanoparticle suspensions after purification and freeze-drying for all investigated molecular micelles (PDI < 0.100). The nanoparticle suspensions synthesized using molecular micelles were the most stable after dialysis and freeze-drying, having low negative zeta potential values ranging from -54 +/- 1.6 mV for poly-L-SULV to -63.2 +/- 0.4 mV for poly-SUS. Transmission electron microscopy (TEM) micrographs showed spherical shape and smooth surface for the PLGA nanoparticles synthesized using molecular micelles. | ||||||||
| 6858 | 3.35 | 8853123 | 1997.05.23 | + | + | Human monocytes stimulation by particles of hydroxyapatite, silicon carbide and diamond: in vitro studies of new prosthesis coatings. | Biomaterials | |
| L Nordsletten, AK Høgåsen, YT Konttinen, S Santavirta, P Aspenberg, AO Aasen, | ||||||||
| Aseptic loosening due to wear and debris formation constitutes the major problem in longevity of joint replacements. Diamond coated onto the prosthesis surface may reduce wear, owing to its excellent tribological properties. A thin diamond coating may be brittle, and we plan eventually to reinforce it with silicon carbide whiskers (SiC). In the present study we compared particles of diamond, SiC and hydroxyapatite (HA) in serum-free cultures of human monocytes. All particles were found to be phagocytozed, and monocyte morphology changed except after the ingestion of diamond. Interleukin-1 beta production was increased on average 30-fold and 38-fold in cultures exposed to HA and SiC, respectively, compared to control and diamond cultures (n = 6). Addition of the phagocytosis inhibitor cytochalasin B inhibited the morphological changes of the monocytes and reduced interleukin-1 beta production. In some experiments particles of polymethylmethacrylate were also included, and the interleukin-1 beta stimulation was in the same range as after HA and SiC stimulation. The results show that diamond particles in serum-free monocyte culture are inert, while SiC and HA have a stimulatory effect comparable to polymethylmethacrylate. With its excellent tribological and biocompatible properties, future studies with diamond coating are warranted. | ||||||||
| 6859 | 3.35 | 16060148 | 2005.09.19 | + | + | Role of free cadmium and selenium ions in the potential mechanism for the enhancement of photoluminescence of CdSe quantum dots under ultraviolet irradiation. | J Nanosci Nanotechnol | |
| R Bakalova, Z Zhelev, R Jose, T Nagase, H Ohba, M Ishikawa, Y Baba, | ||||||||
| The present study describes an enhancement of the photoluminescence of CdSe quantum dots under long-term ultraviolet irradiation in organic solvents. The photoenhancement effect followed multiexponential kinetics and was found to depend on several factors: intensity of ultraviolet light, polarity of the solvent, presence of capping agents on the nanocrystal surface, and presence of free Cd and Se ions in the solution. High intensity ultraviolet irradiation provoked a rapid enhancement of the photoluminescence of CdSe nanocrystals, reaching the maximum with subsequent photoluminescence decay. Low-intensity ultraviolet irradiation provoked a comparatively slow enhancement of the photoluminescence of CdSe nanocrystals, reaching saturation after 5-6 hours of irradiation in organic solvents (butanol and chloroform). The photoenhancement effect was reversible or irreversible depending on the additional ingredients. The role of free Cd and Se in these processes was clarified. The results are discussed in the context of ultraviolet induced liberation of free Cd and Se ions from the nanocrystal surface and their hypothetical reversible deposition with trapping of the surface holes and influencing the efficiency of radiative versus nonradiative exciton decay during the enhancement of photoluminescence. | ||||||||
| 6860 | 3.35 | 15371168 | 2005.02.15 | + | + | Impact of 30-day oral dosing with N-acetyl-L-cysteine on Sprague-Dawley rat physiology. | Int J Toxicol | |
| D Arfsten, E Johnson, A Thitoff, A Jung, E Wilfong, S Lohrke, T Bausman, J Eggers, A Bobb, | ||||||||
| A number of studies have demonstrated a protective effect associated with N-acetyl-l-cysteine (NAC) against toxic chemical exposure. However, the impact of long-term oral dosing on tissue pathology has not been determined. In this study, the authors assessed the impact of long-term oral NAC administration on organ histopathology and tissue glutathione (GSH) and total glutathione-S-transferase (GST) activity levels in Sprague-Dawley (SD) rats. Groups of 20 SD rats (10 males, 10 females), 8 weeks of age, were dosed daily by oral gavage with deionized H2O (negative controls) or NAC solution at a rate of 600 or 1200 mg/kg/day for 30 days. Animals were euthanized 6 h after treatment on study day 30. There were no significant differences in final body weights or weekly average weight gain between treatment groups. Serum alanine aminotransferase (ALT) activities were significantly elevated (p =.05) in NAC-treated animals compared to controls when measured on study day 30. Histopathologic evaluation of the stomach, small intestine, liver, kidneys, spleen, thymus, and lungs revealed no lesions associated with NAC administration. When measured on study day 30, total GST activity for kidney and skin from NAC-treated animals were increased 39% to 131% as compared to controls. Tissue GSH concentrations from NAC-treated animals were increased 24% to 81% as compared with negative controls. Further studies are needed to determine if the observed increase in tissue GSH concentration and GST activity provide a degree of chemoprotection against dermal and systemic chemical toxicants. | ||||||||
| 6861 | 3.34 | 15745010 | 2006.01.06 | + | + | Photoinduced adsorption of hydrogen and methane on gamma-alumina. the photoinduced chesorluminescence (PhICL) effect. | Langmuir | |
| NS Andreev, AV Emeline, SV Polikhova, VK Ryabchuk, N Serpone, | ||||||||
| Adsorption of hydrogen and methane on a preirradiated surface of gamma-Al2O3 produces an afterglow, which has been described as a photoinduced chesorluminescence (PhICL), whose spectral features identify with the intrinsic photoluminescence of alumina. The emission spectrum consists of at least four overlapping single emission bands. For methane adsorption, the PhICL phenomenon is seen only if the solid is preirradiated in the presence of oxygen. Emission decay kinetics of the PhICL effect for gamma-Al2O3 reveal two wavelength regimes: a short wavelength regime at lambda = 300-370 nm (decay time tau = 1.1 +/- 0.2 s; signal width = 2.8 s), and a longer wavelength regime at lambda = 380-700 nm (decay time tau = 2.1 +/- 0.1 s; signal width = 4.3 s). A model is proposed in which there exist two different emission centers and, thus, two different pathways for emission decay. In the first, emission originates with electron trapping by such deep energy traps as anion vacancies {e- + Va --> F+ + hv1} to yield electron F-type color centers, whereas in the second, emission originates from electron/trapped hole recombination {e- + Os*- --> Os2- + hv2}. The first common step of the pathways is homolytic dissociative chemisorption of hydrogen and methane upon interaction with surface-active hole centers Os*-, produced upon preirradiation of alumina, to give atomic hydrogen H* and methyl radicals CH3*. Thermoprogrammed desorption spectra of photoadsorbed or postsorbed oxygen show that adsorbed oxygen interacts with atomic hydrogen and methyl radicals. The products of thermodesorption were H2O for hydrogen and H2O, CO2, and CH3CH3 for methane. The Solonitsyn memory effect coefficient was also evaluated for oxygen photoadsorption. | ||||||||
| 6862 | 3.34 | 17109414 | 2007.06.26 | + | + | Investigation of in vitro biocompatibility of novel pentablock copolymers for gene delivery. | J Biomed Mater Res A | |
| A Agarwal, R Unfer, SK Mallapragada, | ||||||||
| Novel pentablock copolymers of poly(diethylaminoethylmethacrylate) (PDEAEM), poly(ethylene oxide) (PEO), and poly(propylene oxide) (PPO), (PDEAEM-b-PEO-b-PPO-b-PEO-b-PDEAEM), were synthesized as vectors for gene delivery, and were tested for their biocompatibility on SKOV3 (human ovarian carcinoma) and A431 (human epidermoid cancer) cell lines under different in vitro conditions using various assays to elucidate the mechanism of cell death. These copolymers form micelles in aqueous solutions and can be tuned for their cytotoxicity by tailoring the weight percentage of their cationic component, PDEAEM. Copolymers with higher PDEAEM content were found to be more cytotoxic, though their polyplexes were less toxic than the polycations alone. Pentablock copolymers displayed higher cell viability than commercially available ExGen 500 at similar N:P ratios. While cell death with ExGen was found to be accompanied by an early loss of cell membrane integrity, pentablock copolymers caused very little membrane leakage. Caspase-3/7 assay confirmed that none of these polymers induced apoptosis in the cells. These pentablock copolymers form thermo-reversible gels at physiological temperatures, thereby enabling controlled gene delivery. Toxicity of the polymer gels was tested using an agarose-matrix, simulating an in vivo tumor model where injected polyplex gels would dissolve to release polyplexes, diffusing through tumor mass to reach the target cells. Twenty five weight percent of copolymer gels were found to be nontoxic or mildly cytotoxic after 24 h incubation. Transfection efficiency of the copolymers was found to be critically correlated to cytotoxicity and depended on DNA dose, polymer concentration, and N:P ratios. Transgene expression obtained was comparable to that of ExGen, but ExGen exhibited greater cell death. | ||||||||
| 6863 | 3.34 | 12908309 | 2003.09.10 | + | + | Bimetallic catalyst for synthesizing quasi-aligned, well-graphitized multiwalled carbon nanotube bundles on a large scale by the catalytic chemical vapor deposition method. | J Nanosci Nanotechnol | |
| K Mukhopadhyay, GN Mathur, | ||||||||
| An effective method of growth by catalytic chemical vapor deposition (CCVD) to get a large-scale yield of carbon nanotubes is reported. In this method, acetylene is decomposed catalytically over well-dispersed metal particles (Co-Fe and Co-Ni) embedded in commercially available zeolite at a lower temperature (600-700 degrees C). The two binary-metal catalysts (Co-Fe and Co-Ni) used are compared by scanning electron microscopy (SEM) and transmission electron microscopy (TEM). Crucial reaction parameters, such as reaction time, temperature, and the effect of purity of gas to obtain optimum production of the nanotubes, both qualitatively and quantitatively, are also reported. | ||||||||
| 6864 | 3.34 | 14624526 | 2004.08.03 | + | + | Fabrication and in vitro testing of polymeric delivery system for condensed DNA. | J Biomed Mater Res A | |
| YC Huang, M Connell, Y Park, DJ Mooney, KG Rice, | ||||||||
| Polyethylenimine (PEI) was combined with plasmid DNA and freeze dried following the addition of sucrose as a lyoprotectant and pore-forming agent. Freeze-dried PEI DNA condensates were dry mixed with granular polylactideglycolic acid (PLGA) then compression molded and sponged to encapsulated PEI DNA. A measurement of the elastic modulus indicated that 91 wt% sucrose substituted for 95 wt% sodium chloride as a porogen, resulting in PLGA sponges with a mechanical modulus of 100 kPa. The PEI DNA was retained (80%) within PLGA sponges prepared with sucrose during the leaching and subsequent 2-week release studies, whereas sodium chloride PLGA sponges caused the premature release (100%) of PEI DNA within 2 days. In vitro gene transfer studies with PEI DNA PLGA sponges established that adherent and infiltrating fibroblasts expressed reporter gene for 15 days compared with the short, 3-day expression mediated by direct gene of PEI DNA on cells in culture. The results demonstrate an approach to encapsulate condensed DNA in a PLGA sponge for the purpose of retaining DNA within the matrices and creating efficient gene transfer during tissue engineering. | ||||||||
| 6865 | 3.34 | 17624699 | 2008.01.24 | + | + | Encapsulation of moxifloxacin within poly(butyl cyanoacrylate) nanoparticles enhances efficacy against intracellular Mycobacterium tuberculosis. | Int J Pharm | |
| KO Kisich, S Gelperina, MP Higgins, S Wilson, E Shipulo, E Oganesyan, L Heifets, | ||||||||
| Macrophages in the lungs are the most important cell type supporting replication of Mycobacterium tuberculosis in humans. The objective of this study was to investigate whether the effect of moxifloxacin against M. tuberculosis residing in macrophages could be improved by encapsulation of the drug in the biodegradable nanoparticles, which are known to accumulate in macrophages upon intravenous administration. To accomplish this, moxifloxacin was encapsulated in poly(butyl cyanoacrylate) (PBCA) nanoparticles. Encapsulated moxifloxacin accumulated in macrophages approximately three-fold times more efficiently than the free drug, and was detected in the cells for at least six times longer than free moxifloxacin at the same extracellular concentration. Inhibition of intracellular M. tuberculosis growth with encapsulated moxifloxacin was achieved at the concentration of 0.1microg/ml, whereas the same effect with free MX required a concentration of 1microg/ml. Nanoparticles observed within the macrophage cytoplasm were distributed throughout the cytoplasm, sometimes in the vicinity of intracellular bacteria. | ||||||||
| 6866 | 3.34 | 17574291 | 2007.11.05 | + | + | Paclitaxel distribution in poly(ethylene glycol)/poly(lactide-co-glycolic acid) blends and its release visualized by coherent anti-Stokes Raman scattering microscopy. | J Control Release | |
| E Kang, J Robinson, K Park, JX Cheng, | ||||||||
| Mechanisms underlying the release of paclitaxel (PTX) from poly(ethylene glycol)/poly(lactic-co-glycolic acid) (PEG/PLGA) blends were investigated by coherent anti-Stokes Raman scattering (CARS) microscopy. PLGA, PEG, and PTX were selectively imaged by using the resonant CARS signal from the CH3, CH2, and aromatic CH stretch vibrations, respectively. Phase segregation was observed in PLGA films containing 10 to 40 wt.% PEG in the absence of PTX loading. The PEG phase existed in the form of crystalline fibers in the (8:2, weight ratio) and (7:3) PLGA/PEG films. CARS observation indicated that PTX preferentially partitioned into the PEG domains in the (9:1) and (8:2) PLGA/PTX films, but exhibited a uniform mixing with both PLGA and PEG in the (7:3) PLGA/PEG film. The solid dispersion of PTX into PEG domains was attributed to a strong interaction between PTX and PEG, supported by the disappearance of PEG crystallization in the PTX-loaded PLGA/PEG film evidenced through X-ray diffraction analysis. PTX release was induced by exposing the film to an aqueous solution and monitored in real time by CARS and two-photon fluorescence microscopy. Fast dissolution of both PEG and PTX was observed at the film surface. Upon infiltration of water into the film, the PEG domains were rearranged into ring structures enriched by both PTX and PEG. The CARS data provided visual evidence explaining the accelerated burst release followed by more sustained release of PTX from the PLGA/PEG films as measured by HPLC. | ||||||||
| 6867 | 3.34 | 11223020 | 2001.06.21 | + | + | Acidic pH promotes the formation of toxic fibrils from beta-amyloid peptide. | Brain Res | |
| Y Su, PT Chang, | ||||||||
| Beta-amyloid (Abeta) peptides, the major component of senile plaques in brains of patients with Alzheimer's disease (AD), were found in the low pH organelles (i.e. endosome/lysosome) of cultured neuronal cells. Since acidic pH values have been shown to promote the self-assembly of Abetas, which seems to be a prerequisite for their neuropathogenicity, elucidating the aggregation behavior of Abetas in acidic environments and their subsequent effects on neuronal cells may be crucial for understanding the neurodegenerative process of AD. In this study, the extent and rate of aggregation of Abeta(1-42) peptides at pH values of 5.8 and 7.4, as well as the structure and neurotoxic effects of these aggregates, were examined. We showed that Abeta(1-42) peptides formed large and complex fibrils much more efficiently at acidic rather than neutral pH. Furthermore, only the pH 5.8 Abeta aggregates induced significant apoptotic death of PC12 cells, as indicated by a decrease in 3-(4,5-dimethylthiazol-2-yl)2,5-diphenyltetrazolium bromide (MTT) reduction and an increase in phosphatidylserine externalization. Taken together, our results suggest that the Abetas present in the acidic organelles may form neurotoxic fibrils more easily than those in the neutral cellular compartments. | ||||||||
| 6868 | 3.34 | 8026803 | 1994.08.05 | + | + | Bleaching of membrane-bound merocyanine 540 in conjunction with free radical-mediated lipid peroxidation. | Free Radic Biol Med | |
| TJ Pintar, F Lin, AW Girotti, | ||||||||
| The lipophilic dye merocyanine 540 (MC540) can photosensitize potentially lethal cell membrane damage as well as its own degradation (bleaching). Photobleaching in a test membrane, the human erythrocyte ghost has been examined. White light irradiation of MC540-sensitized ghosts resulted in lipid hydroperoxide (LOOH) formation, low-level thiobarbituric acid (TBA) reactivity, and dye bleaching (A568 decay). When the reaction was carried out in the presence of ascorbate (AH-), and added Fe3+, there was a large enhancement of TBA reactivity (indicative of free radical-mediated lipid peroxidation) and concomitant increase in the rate of photobleaching. Rapid bleaching also occurred when MC540 was incubated in the dark with ghosts that had been photoperoxidized with another dye (a phthalocyanine) and then exposed to AH-. The extent of bleaching in this system was found to be proportional to the starting level of LOOH. Like the wave of free radical lipid peroxidation that accompanied it, dye bleaching in AH(-)-treated, preperoxidized ghosts was stimulated by supplemental Fe3+, inhibited by desferrioxamine or butylated hydroxytoluene (BHT), but unaffected by catalase or superoxide dismutase. From this and related evidence, we deduce that: (1) in the absence of Fe3+/AH-, photoperoxidation and photobleaching occur independently and are nonradical, singlet oxygen-mediated processes; and (2) in the presence of Fe3+/AH-, 1-electron reduction of photogenerated LOOHs results in a surge of lipid peroxidation that amplifies dye loss via free radical processes. MC540 bleaching might be exploited as a relatively simple and sensitive indicator of lipid autoxidation in isolated membranes and cells. | ||||||||
| 6869 | 3.34 | 15840437 | 2005.06.01 | + | + | Cytotoxic effect of formaldehyde with free radicals via increment of cellular reactive oxygen species. | Toxicology | |
| Y Saito, K Nishio, Y Yoshida, E Niki, | ||||||||
| It is well known that formaldehyde (HCHO) and reactive oxygen species (ROS), such as free radicals, are cytotoxic as well as potentially carcinogenic. Although the individual effects of these reactants on cells have been investigated, the cytotoxicity exerted by the coexistence of HCHO and reactive radicals is poorly understood. The present study using Jurkat cells demonstrated that the coexistence of HCHO with water-soluble radical initiator, 2,2'-azobis-[2-(2-imidazolin-2-yl)propane] dihydrochloride (AIPH) dramatically decreased cell viability, and that under such conditions scant cell death was observable induced by either of the reactants alone. Based on the results of phosphatidylserine exposure and caspase activation, this observed cell death, in fact, was apparently necrotic rather than apoptotic. To understand the mechanisms of the cell toxicity of HCHO and AIPH, we assessed two kinds of oxidative stress markers such as cellular glutathione (GSH) content and cellular ROS, and the DNA-protein cross-links, which formed as the result of HCHO treatment. A marked decrease in total cellular GSH was observed not only in the case of the coexistence conditions but also with AIPH alone. Dichlorodihydrofluorescein (DCF) assay revealed that cellular ROS were synergistically increased before cell death. The formation of DNA-protein cross-links was observed in the presence of HCHO and AIPH, and the extent was similar to HCHO alone. Co-incubation with semicarbazide, which inactivates HCHO, prevented this cell death induced by a combination of HCHO and AIPH. Semicarbazide also exhibited an inhibitory effect on the synergistic increment of cellular ROS and the formation of DNA-protein cross-links. These results suggest that the free radicals from AIPH induced GSH reduction, while HCHO resulted in the formation of DNA-protein cross-links, eventuating in a synergistic, incremental increase of cellular ROS and cell death brought about by this combination. | ||||||||
| 6870 | 3.33 | 17521151 | 2007.07.24 | + | + | Biokinetics and tolerance development of toxic metals in Daphnia magna. | Environ Toxicol Chem | |
| MT Tsui, WX Wang, | ||||||||
| Daphnia magna is widespread in many freshwater systems of temperate regions and frequently is used to test metal toxicity. Recently, studies have been performed to determine metal biokinetics and development of tolerance in this important zooplankton species. In the present paper, we review the recent progress in these areas and suggest possible directions for future studies. Substantial differences exist in aqueous uptake, dietary assimilation, and elimination of several metals (Cd, Se, Zn, Ag, Hg, and MeHg) by D. magna. The routes of uptake are metal-specific, with Se and MeHg being accumulated predominantly through diet. All metals except Ag can be biomagnified from algae to D. magna, providing that metal concentrations in algae and algal food density are relatively low. Methylmercury is biomagnified in all situations. As a route for metal elimination in D. magna, maternal transfer is especially important for Se, Zn, and MeHg. On the other hand, the effect of single-generation exposure to metals on D. magna is very different from multigeneration exposure, which often results in a significantly higher metal tolerance. Moreover, D. magna easily loses metal tolerance developed through long-term exposure. Recovery from metal stress can temporarily increase the sensitivity of D. magna to metal toxicity. Finally, metallothionein-like protein is responsible for minimizing metal toxicity in D. magna. The results inferred from these studies can be extrapolated to other aquatic invertebrates as well as to other pollutants in the aquatic environment. | ||||||||
| 6871 | 3.33 | 17716133 | 2007.09.18 | + | + | Use of degradable and nondegradable nanomaterials for controlled release. | Nanomed | |
| WK Wan, L Yang, DT Padavan, | ||||||||
| Drug-delivery devices are fundamentally important in improving the pharmacological profiles of therapeutic molecules. Nanocontrolled-release systems are attracting a lot of attention currently owing to their large surface area and their ability to target delivery to specific sites in the human body. In addition, they can penetrate the cell membrane for gene, nucleic acid and bioactive peptide/protein delivery. Representative applications of nanodrug-delivery systems include controlled-release wound dressings, controlled-release scaffolds for tissue regeneration and implantable biodegradable nanomaterial-based medical devices integrated with drug-delivery functions. We review the present status and future perspectives of various types of nanocontrolled-release systems. Although many of the well-established degradable and nondegradable controlled-release vehicles are being investigated for their processing into nanocarriers, several new emerging nanomaterials are being studied for their controlled-release properties. The release of multiple bioactive agents, each with its own kinetic profile, is becoming possible. In addition, integration of the nanocontrolled-release systems with other desirable functions to create new, cross-discipline applications can also be realized. | ||||||||
| 6872 | 3.33 | 16973314 | 2006.12.12 | + | + | Formation of self-organized nanoparticles by lecithin/chitosan ionic interaction. | Int J Pharm | |
| F Sonvico, A Cagnani, A Rossi, S Motta, MT Di Bari, F Cavatorta, MJ Alonso, A Deriu, P Colombo, | ||||||||
| In this work the production of auto-assembled nanoparticles obtained by the mixing of chitosan and lecithin is presented. The size and surface charge of the nanoparticles were studied as function of the weight ratio between components, the viscosity of the polysaccharide and the pH of the colloidal suspension. In order to elucidate the structure of nanoparticles, micro-FT-IR and elastic neutron scattering experiments have been performed. Results evidenced a strong electrostatic interaction between components and a structure that is neither that of homogeneous spheres nor of coated unilamellar vesicles. Preliminary encapsulation experiments with progesterone, as model lipophilic drug, showed good encapsulation efficiencies. | ||||||||
| 6873 | 3.33 | 17193393 | 2007.02.16 | + | Top-down fabrication of semiconductor nanowires with alternating structures along their longitudinal and transverse axes. | Small | ||
| Y Sun, RA Graff, MS Strano, JA Rogers, | ||||||||
| 6874 | 3.33 | 12775513 | 2003.07.01 | + | + | Response of alveolar macrophages from inducible nitric oxide synthase knockout or wild-type mice to an in vitro lipopolysaccharide or silica exposure. | J Toxicol Environ Health A | |
| PC Zeidler, JR Roberts, V Castranova, F Chen, L Butterworth, ME Andrew, VA Robinson, DW Porter, | ||||||||
| The role of nitric oxide (NO) in pulmonary disease has been controversial with both antiinflammatory (scavenging radicals and inhibiting NF-êB activation) and proinflammatory (forming highly reactive peroxynitrite and augmenting NF-êB activation by inflammatory agents) actions reported. Therefore, a study has been initiated to determine whether deletion of the inducible nitric oxide synthase (iNOS) gene in the C57BL/6J mouse alters the pulmonary macrophage response to lipopolysaccharide (LPS) or silica. The objective of the initial phase of this study was to determine the difference in responsiveness of alveolar macrophages (AMs), harvested from naive wild-type (WT) or iNOS knockout (iNOS KO) mice, to an in vitro LPS or silica exposure. Primary AMs were obtained by bronchoalveolar lavage (BAL) from age- and weight-matched iNOS KO and WT mice. The cells were treated with interferon-gamma (IFN-ã) (50 U/ml), IFN-ã (50 U/ml) + LPS (1 microg/ml), LPS (0.01-100 microg/ml), or silica (25-250 microg/ml). The following parameters were measured: nitrate and nitrite (NOx), tumor necrosis factor-á (TNF-á), macrophage inflammatory protein-2 (MIP-2), intracellular generation of the reactive oxygen species (ROS) hydrogen peroxide (H(2)O(2) and superoxide (O(*-2)), and basal (unstimulated) total antioxidant capacity. Data show a significant increase in NOx production upon exposure to IFN-ã +/- LPS in the WT but not iNOS KO AMs. NOx production by iNOS KO or WT AMs was not altered by in vitro exposure to LPS or silica alone. LPS, but not silica, induced TNF-á and MIP-2 production in both iNOS KO and WT AMs. Statistical analysis of concentration response curves found a significant tendency for greater mediator production in the iNOS KO versus WT AMs. Basal intracellular production of H(2)O(2) and O(*- 2) was significantly greater in the iNOS KO compared to WT AMs. In contrast, LPS- (10 microg/ml) or silica- (100 microg/ml) stimulated intracellular oxidant production was lower in iNOS KO AMs, but overall (basal + stimulated) inflammatory capacity was similar between the cell types. The basal total antioxidant production of the iNOS KO AMs was approximately twofold higher than the WT AMs. In conclusion, certain compensatory changes appear to occur in AMs from iNOS KO mice. In response to the inability to induce NO production, iNOS KO AMs exhibit significantly higher basal generation of H(2)O(2) and (O(*- 2)) as well as higher total antioxidant levels. In addition, LPS induced TNF-á and MIP-2 production tend to be higher in AMs from iNOS KO mice. Such compensatory changes in the AM response may affect the response of iNOS KO mice to inflammatory exposures. | ||||||||
| 6875 | 3.33 | 15516875 | 2005.02.25 | + | + | Comparative investigation of the biocompatibility of various silicon nitride ceramic qualities in vitro. | J Mater Sci Mater Med | |
| A Neumann, T Reske, M Held, K Jahnke, C Ragoss, HR Maier, | ||||||||
| There is a controversy about the biocompatibility of silicon nitride ceramics contained in the literature, which appears to be related to a factor of the individual chemical composition of different qualities of silicon nitride ceramics and of the different surface properties. This study attempts to investigate the cytotoxicity of different qualities of industrial silicon nitride ceramics applying an L929-cell culture model in a direct contact assay combined with a cell viability assessment. Five different qualities of industrial standard silicon nitride ceramics were chosen for in vitro testing. The chemical composition was determined by EDS analysis. Different biomedically approved aluminium oxide qualities, a titanium alloy, glass and polyvinylchloride (PVC) served as control materials. L929 mice fibroblasts were incubated directly on the materials for 24 h, stained with bisbenzimide and propidium iodine for double fluorochromasia viability testing, and evaluated by inversion-fluorescence microscopy to control cell morphology, viability and cell counts compared to empty well values. Scanning electron microscopy was applied to additionally investigate cell morphology. There was no observation of cytotoxic effects on the silicon nitride ceramic samples; moreover cell morphology remained the same as on aluminium oxide and titanium. Viability testing revealed the presence of avital cells exclusively on PVC, which served as a negative control. Cell counts on all polished surfaces showed significantly higher numbers, whereas some rough surface samples showed significantly lower numbers. We conclude that silicon nitride ceramics show no cytotoxic effects and should be considered for biomedical application owing to its favourable physiochemical properties, especially its superior resistance to mechanical stress, which would be useful for compression loaded conditions. Polished surfaces would appear to promote advanced biocompatibility. | ||||||||
| 6876 | 3.33 | 16042439 | 2006.06.22 | + | + | Brush-type amphiphilic diblock copolymers from "living"/controlled radical polymerizations and their aggregation behavior. | Langmuir | |
| Z Cheng, X Zhu, ET Kang, KG Neoh, | ||||||||
| Two brush-type amphiphilic diblock copolymers, poly(poly(ethylene glycol)methyl ether methacrylate-block-polystyrene) (P(PEGMA)-b-PS) and poly(glycidyl methacrylate)-block-poly(poly(ethylene glycol)methyl ether methacrylate) (P(GMA)-b-P(PEGMA)) were synthesized, respectively, via consecutive atom-transfer radical polymerizations (ATRPs) and reversible addition-fragmentation chain-transfer (RAFT) polymerizations. The diblock copolymers were characterized by gel permeation chromatography (GPC), (1)H nuclear magnetic resonance (NMR) spectroscopy, and FT-IR spectroscopy. The aggregation behavior of the two amphiphilic diblock copolymers in water was also studied. Scanning electron and transmission electron microscopic images revealed that spherical micelles (40-80 nm in diameter) from self-assembly of the P(PEGMA)-b-PS copolymers and wormlike micelles (60-120 nm in length and 20-30 nm in diameter) from self-assembly of the P(GMA)-b-P(PEGMA) copolymers were prevalent. The spherical P(PEGMA)-b-PS micelles could self-assemble gradually into giant aggregates of several micrometers in diameter. | ||||||||
| 6877 | 3.32 | 16731555 | 2006.10.05 | + | + | Atomic force microscopy study of the specific adhesion between a colloid particle and a living melanoma cell: Effect of the charge and the hydrophobicity of the particle surface. | Biophys J | |
| CE McNamee, N Pyo, K Higashitani, | ||||||||
| We investigated the effect of the charge and the hydrophobicity of drug delivery system (DDS) carriers on their specificity to living malignant melanoma B16F10 cells with the atomic force microscope. To model various nanoparticle DDS carriers, we used silica particles that were modified with silane coupling agents. We then measured the compression and decompression forces between the modified colloid probes and the living B16F10 cell in a physiological buffer as a function of their separation distances. The maximum adhesive force on decompression was related to the strength of the specificity of the DDS to the malignant cell. A comparison of the average maximum adhesive force of each functionality group surprisingly showed that negatively charged surfaces and hydrophobic modified surfaces all had similar low values. Additionally, we saw the unexpected result that there was no observable dependence on the degree of hydrophobicity of the probe surface to a B16F10 cell. Only the positively charged particle gave a strong adhesive force with the B16F10 cell. This indicated that DDS carriers with positive charges appeared to have the highest affinity for malignant melanoma cells and that the use of hydrophobic materials unexpectedly did not improve their affinity. | ||||||||
| 6878 | 3.32 | 11489511 | 2001.12.04 | + | + | Sterically stabilized polyplex: ligand-mediated activity. | J Control Release | |
| MC Woodle, P Scaria, S Ganesh, K Subramanian, R Titmas, C Cheng, J Yang, Y Pan, K Weng, C Gu, S Torkelson, | ||||||||
| Synthetic vectors have been considered as a safer and more versatile alternative to viral-based gene delivery systems. A variety of very simple synthetic vector systems, e.g., cationic lipid- and polymer-complexed plasmid DNA have activity in vivo but it appears to be mediated by non-specific electrostatic interactions limiting targeting. In order to avoid these problems, we designed a sterically stabilized layered colloidal system. The steric polymer coating reduces non-specific interactions. We have synthesized a PEG conjugate of PEI that complexes DNA to form small, stable colloids with a steric polymer coat on their surface. The polymer enhances colloidal stability and reduces non-specific binding and toxicity. It also renders the complex inactive presumably due to reduced binding. Ligands are then appended to the distal end of the steric polymer to restore cell binding and expression at target cells. We prepared conjugates with RGD peptide ligands appended to the distal end of the steric polymer. The resulting conjugates also form complexes but with ligands exposed on their surface restoring binding and activity. Labeled oligonucleotides and DNA were used to measure intracellular distribution. Oligonucleotides are found localized in the nucleus, whereas the labeled plasmid DNA remained in the cytoplasm. Import of plasmid DNA into the nucleus appears to be very inefficient yet sufficient for expression. | ||||||||
| 6879 | 3.32 | 18204984 | 2008.05.27 | + | + | Toxicity of Anllóns River sediment extracts using microtox and the zucconi phytotoxicity test. | Bull Environ Contam Toxicol | |
| R Devesa-Rey, AB Moldes, F Díaz-Fierros, MT Barral, | ||||||||
| Two methods of environmental toxicological tests were compared and applied to bed sediments of the Anllóns River: the standardized toxicological test based on inhibition of luminescence employing Vibrio fischeri, and a phytotoxicity test, using garden cress (Lepidium sativum L.), water cress (Nasturtium officinalis L.) and annual rye-grass (Lolium multiflorum L.) seeds. In addition, TCLP and HCl extracts were evaluated. The inhibition of luminescence test showed more sensitivity to toxicants than phytotoxicity assays, and no significant correlations were found between them. On the other hand, TCLP metal concentrations (Fe, Al, Zn, Pb, As) were lower than HCl concentrations, but seemed to represent more accurately the phytoavailability of metals to plants. | ||||||||
| 6880 | 3.32 | 12359386 | 2003.01.14 | + | + | The relative importance of water and food as cadmium sources to Daphnia magna Straus. | Aquat Toxicol | |
| C Barata, SJ Markich, DJ Baird, AM Soares, | ||||||||
| Knowledge of the transport pathways of metals into aquatic organisms is paramount in determining the metal's potential mechanism of toxicity. To determine the relative importance of water and food as cadmium (Cd) sources for the cladoceran Daphnia magna grazing on the algae Chlorella vulgaris, we measured cadmium accumulation and toxicity (feeding inhibition and survival) in three genetically different clones of D. magna subsequent to water, food, and water and food exposures. We found that Cd uptake from water and food was independent of source and additive in effect, with D. magna juveniles accumulating twice as much Cd from water than from food (algae). However, the efficiency with which Cd was assimilated by D. magna from its algal diet was much higher (10%) than from water (0.3%). Uptake and toxic responses were inversely related: tolerant clones accumulated more Cd. As a consequence, models based on uptake of metals from the combined routes of water and food may be reliable to predict metal dynamics in the field, but may fail to predict toxic effects since tolerance to metals is not necessarily linked to reduced total uptake of metals. | ||||||||
| 6881 | 3.32 | 15251181 | 2005.02.28 | + | + | Modulating activity of fullerol C60(OH)22 on doxorubicin-induced cytotoxicity. | Toxicol In Vitro | |
| G Bogdanović, V Kojić, A Dordević, J Canadanović-Brunet, M Vojinović-Miloradov, VV Baltić, | ||||||||
| Paper presents the effects of the newly synthesized fullerol C60(OH)22 on the growth of tumor cells in vitro and its modulating activity on doxorubicin (DOX)-induced cytotoxicity in human breast cancer cell lines. Cell growth inhibition was evaluated by tetrazolium colorimetric WST1 assay. Electron spin resonance (ESR) "trapping" method was used to investigate OH-radical scavenger activity of fullerol during Fenton's reaction. At a range of nanomolar concentrations fullerol induced cell growth inhibition, which was cell line, dose and time dependent. Fullerol also strongly suppressed DOX-induced cytotoxicity at all concentrations regardless the time of fullerol addition. Proanthocyanidins added as single agent to MCF-7 cell culture for 48 h induced low growth inhibition but in combination with DOX strongly decreased DOX cytotoxicity. Fullerol was found to be a potent hydroxyl radical scavenger: the relative intensity of ESR signals of DMPO-hydroxyl radical (DMPO-OH) spin adduct decreased by 88% in the presence of 0.5 microg/ml of fullerol. The obtained results suggest that antiproliferative effect of the fullerol and its protective effect on DOX-induced cytotoxicity might be mediated through hydroxyl-radical scavenger activity of C60(OH)22. | ||||||||
| 6882 | 3.32 | 8920711 | 1996.12.18 | + | + | The carcinogenic potency of carbon particles with and without PAH after repeated intratracheal administration in the rat. | Toxicol Lett | |
| C Dasenbrock, L Peters, O Creutzenberg, U Heinrich, | ||||||||
| The role of carcinogenic PAH in soot- and carbon black-related lung tumour induction in rats was investigated after intratracheal administration of carbon blacks (CB) and two types of diesel soot (DS), either as original or as toluene extracted particles. The total particle dose per animal was 15 mg subdivided into 16-17 weekly applications. There was one vehicle control and two groups were treated with a total dose of either 30 or 15 mg pure BaP as positive control. The main tumour results were: (a) original DS induced a higher tumour rate than extracted DS; (b) the carcinogenic potency of extracted CB probably depends on the size of the primary carbon particles and on the specific surface area of the particles; (c) extracted DS covered with 11 micrograms BaP per mg carbon particles caused a lower lung tumour rate than original DS containing only 0.9 ng BaP per mg, but a variety of other PAH and NO2-PAH; (d) a total dose of 15 mg pure BaP caused a lung tumour rate very similar to that of 30 mg extracted DS, 15 mg original DS or 15 mg Printex 90T CB extracted or covered with approximately 29.5 micrograms BaP per mg CB. | ||||||||
| 6883 | 3.31 | 2753008 | 1989.08.29 | + | + | Talc deposition and effects after 20 days of repeated inhalation exposure of rats and mice to talc. | Environ Res | |
| JA Pickrell, MB Snipes, JM Benson, RL Hanson, RK Jones, RL Carpenter, JJ Thompson, CH Hobbs, SC Brown, | ||||||||
| The relationship between the inhalation exposure concentration of talc and the resulting lung burdens and histologic lesions was studied using groups of 20 F344/Crl rats and 20 B6C3F mice (10 male and 10 female) exposed to one of three concentrations of asbestos-free talc for 6 hr/day, 5 days/week for 4 weeks. Controls were exposed to filtered air using the same schedule. The pulmonary retention of talc and the development of pulmonary pathology were evaluated. The mass median aerodynamic diameter (MMAD) of the talc aerosol was 3.0 microns with a geometric standard deviation (sigma g) of 1.9. The mean exposure concentrations for rats were 0, 2.3, 4.3, and 17 mg talc/m3. Lung burdens in rats averaged 0, 0.07, 0.17, and 0.72 mg talc/g lung after the 20-day inhalation exposure; thus, the amount retained in the lung per unit of exposure concentration increased with increasing concentration. Mean exposure concentrations for the mice were 0, 2.2, 5.7, and 20.4 mg of talc/m3, which resulted in lung burdens of 0, 0.10, 0.29, and 1.0 mg talc/g lung; thus, the relationship between exposure concentration and the amount retained in the lung was approximately constant. Lung burdens from this study were used to project lung burdens that would result from longer exposures of rodents and man. No clinical signs were observed in the rats or mice prior to sacrifice 24 hr after the last exposure day. Histologic alterations in lung tissue consisted of only a modest, diffuse increase of talc-containing, free macrophages within alveolar spaces in both rat and mouse groups exposed to the highest level of talc for 20 days. A model simulating chronic talc inhalation exposure of rats and mice predicted lung burdens of 2-3 mg talc/g lung (wet wt) if animals were exposed to 17 mg talc/m3 for 2 years, and deposition and clearance of talc were unchanged by continued exposure. A potential limitation in this modeling is that if clearance of talc is delayed by continued exposure, the accumulated talc lung burdens would be higher than those projected by the simulation model. Humans exposed to aerosols of respirable talc are projected to accumulate much higher lung burdens than would occur in rodents exposed to the same aerosol, because humans have a higher estimated deposition fraction and slower estimated clearance of the deposited talc dust. Equilibrium lung burdens of greater than or equal to 2 mg talc/g lung were predicted for human exposures at or near the TLV for talc. | ||||||||
| 6884 | 3.31 | 17713959 | 2007.11.13 | + | + | Rayleigh imaging of graphene and graphene layers. | Nano Lett | |
| C Casiraghi, A Hartschuh, E Lidorikis, H Qian, H Harutyunyan, T Gokus, KS Novoselov, AC Ferrari, | ||||||||
| We investigate graphene and graphene layers on different substrates by monochromatic and white-light confocal Rayleigh scattering microscopy. The image contrast depends sensitively on the dielectric properties of the sample as well as the substrate geometry and can be described quantitatively using the complex refractive index of bulk graphite. For a few layers (<6), the monochromatic contrast increases linearly with thickness. The data can be adequately understood by considering the samples behaving as a superposition of single sheets that act as independent two-dimensional electron gases. Thus, Rayleigh imaging is a general, simple, and quick tool to identify graphene layers, which is readily combined with Raman scattering, that provides structural identification. | ||||||||
| 6885 | 3.31 | 9679447 | 1998.08.24 | + | + | Influence of solvent polarity and proticity on the photochemical properties of norfloxacin. | Photochem Photobiol | |
| P Bilski, LJ Martinez, EB Koker, CF Chignell, | ||||||||
| The fluoroquinolone antibacterial norfloxacin (NF) is a moderate photosensitizer of singlet molecular oxygen (1O2). We have studied photosensitization by NF as a function of medium polarity and proticity in solvent mixtures. We have used 1,4-dioxane and propylene carbonate mixtures to keep proticity constant while modulating polarity, and water/D2O and ethylene carbonate mixtures to alter proticity without large changes in polarity. The absorption spectrum of NF was little affected by solvent changes, as compared to the fluorescence spectrum that exhibited as much as a 50 nm blue-shift, e.g. 1,4-dioxane versus D2O. The quantum yield of NF fluorescence saturated at an almost 10 times higher value (approximately 0.14) when proticity was increased by added water, up to 0.2 mol fraction, to ethylene carbonate. Less pronounced, the increasing polarity in 1,4-dioxane/propylene carbonate mixtures affected the fluorescence yield much less. Norfloxacin produces 1O2 and is able to quench 1O2. The rate constant for 1O2 quenching is 4.5 x 10(7) M-1 s-1 in propylene carbonate but decreases ca four times in D2O. The quantum yield of 1O2 photogeneration was also up to five times higher in solvents that were both protic and polar than vice versa. Our data show that NF is more photochemically active in an environment that is both protic and polar. This suggests the involvement of polar excited state(s) and possible proton/hydrogen transfer during photoexcitation. Similar processes may initiate the phototoxic response reported in some patients treated with the fluoroquinolone drugs. The phototoxicity of NF and other fluoroquinolone antibiotics may strongly depend on their localization in hydrophilic or hydrophobic cell/tissue regions. | ||||||||
| 6886 | 3.30 | 12425649 | 2003.08.13 | + | + | Secondary structure of proteins adsorbed onto or embedded in polyelectrolyte multilayers. | Biomacromolecules | |
| P Schwinté, V Ball, B Szalontai, Y Haikel, JC Voegel, P Schaaf, | ||||||||
| The structural changes of bovine serum albumin (BSA) and hen egg white lysozyme (HEL) upon their adsorption onto the surface or their embedding into the interior of poly(allylamine hydrochloride)-(poly(styrenesulfonate) (PAH-PSS) multilayer architectures were investigated by attenuated total reflection Fourier transform infrared (ATR-FTIR) spectroscopy. The presence of the polyelectrolytes seems, as previously observed for fibrinogen (J. Phys. Chem. B 2001, 105, 11906-11916), to prevent intermolecular interactions and, thus, protein aggregation at ambient temperature. The secondary structure of the proteins was somewhat altered upon adsorption onto the polyelectrolyte multilayers. The structural changes were larger when the charges of the multilayer outer layer and the protein were opposing. The adsorption of further polyelectrolyte layers onto protein-terminated architectures (i.e., embedding the proteins into a polyelectrolyte multilayer) did not cause considerable further changes in their secondary structures. The capacity of the polyelectrolyte architectures to delay the formation of intermolecular beta-sheets upon increasing temperatures was not uniform for the studied proteins. PSS in contact with HEL could largely prevent the heat-induced aggregation of HEL. In contrast, PAH had hardly any effect on the aggregation of BSA. The differences are explained on the basis of protein-polyelectrolyte interactions, affected mostly by the nature and the strength of the ionic interactions between the polyelectrolyte-protein contact surfaces. | ||||||||
| 6887 | 3.30 | 17193142 | 2007.09.24 | + | Incorporating CdTe nanocrystals into polystyrene microspheres: towards robust fluorescent beads. | Small | ||
| Y Yang, Z Wen, Y Dong, M Gao, | ||||||||
| 6888 | 3.30 | 15126289 | 2004.06.17 | + | + | Mitochondrial swelling and generation of reactive oxygen species induced by photoirradiation are heterogeneously distributed. | Ann N Y Acad Sci | |
| TI Peng, MJ Jou, | ||||||||
| Abundant evidence has been gathered to show that overproduction of reactive oxygen species (ROS) can lead to the opening of the mitochondrial permeability transition pore (MPTP) and result in apoptosis in mammalian cells. The information regarding spatial and temporal regulation of intracellular ROS formation related to the MPTP opening, however, is relatively limited. In this study, we used a fluorescent probe, dihydro-2',7'-dichloroforescin (DCF), to detect intracellular ROS levels in different compartments of the cell in a time-resolved manner. The roles of mitochondrial ROS (mROS) in the MPTP opening and mitochondrial membrane potential drop were investigated by using H(2)DCFDA coloaded with a mitochondrial marker dye MitoTracker Red, and by a mitochondrial membrane potential dye tetramethyl rhodamine ethyl ester. We applied multiphoton laser scanning microscopy to avoid autooxidation and bleaching of DCF so that long-term visualization of intracellular ROS formation could be performed. Moreover, we noted that the resting mROS levels of different mitochondria were not homogeneous. After cells had been exposed to photoirradiation, the intracellular ROS gradually increased but the heterogeneity of mROS was maintained. Later, swelling was observed in mitochondria that contained higher levels of ROS, indicating the opening of the MPTP. In cells in which all the mitochondria swelled, they were translocated to the perinuclear area, which became the site of ROS production. At this stage, mROS reached the highest level concomitantly with a complete loss of mitochondrial membrane potential, indicating full opening of the MPTP. At the end, photoirradiation resulted in apoptotic cell death. In summary, we demonstrated by multiphoton laser scanning microscopy that photoirradiation induces heterogeneous intracellular ROS formation and mitochondrial permeability transition pore opening in single intact cells. These observations imply the existence of a microdomain in the regulation of mROS formation and subsequent opening of the MPTP. | ||||||||
| 6889 | 3.30 | 12568458 | 2003.04.04 | + | + | Confounding factors in bioassays with freshwater and marine organisms. | Ecotoxicol Environ Saf | |
| JF Postma, S de Valk, M Dubbeldam, JL Maas, M Tonkes, CA Schipper, BJ Kater, | ||||||||
| The use of bioassays in ecological risk assessments often raises questions about the causative factors, and insight into the possibility that confounding factors, such as pH or increased ammonia concentrations, might be responsible for the observed toxicity is needed. It was decided to develop a practical approach for the Dutch situation, in which a first screening is carried out based on provisional criteria. In collecting the required data, dozens of experiments were performed, while the scientific literature was searched for additional information. It is concluded that the provisional criteria specified are at present useful tools in interpreting results of bioassays. Depending on the outcome and the aim of the research, it might be necessary to further reduce uncertainties in the interpretation. This might require some additional experiments, using alternative controls or test procedures or altering the composition of the original sample. | ||||||||
| 6890 | 3.30 | 17713934 | 2007.11.13 | + | + | Formation of protein-metal oxide nanostructures by the sonochemical method: observation of nanofibers and nanoneedles. | Langmuir | |
| CE Bunker, KC Novak, EA Guliants, BA Harruff, MJ Meziani, Y Lin, YP Sun, | ||||||||
| The sonochemical reaction of iron pentacarbonyl is explored in water and in water with the protein BSA (bovine serum albumen). In water, the reaction is found to produce spherical nanoparticles of magnetite (Fe3O4) with a particle size distribution of <10 to approximately 60 nm. In water with BSA, the reaction produces either nanofibers or nanoneedles, depending on the concentration of BSA. The nanofiber and nanoneedle samples are found to be mixtures of goethite, lepidocrocite, and hematite (alpha-FeOOH, gamma-FeOOH, and alpha-Fe2O3, respectively). The sonochemical reaction of iron pentacarbonyl with BSA in water is thought to proceed through the thermal decomposition mechanism for iron pentacarbonyl with BSA acting as a templating agent. | ||||||||
| 6891 | 3.30 | 3732203 | 1986.09.17 | + | + | Lifetime effects of intratracheally instilled nickel subsulfide on B6C3F1 mice. | Environ Res | |
| GL Fisher, CE Chrisp, DA McNeill, | ||||||||
| A nickel subsulfide (Ni3S2) lung tumor model for the study of metal carcinogenesis was evaluated using intratracheally dosed B6C3F1 mice. A preliminary study of the survival of mice 14 days after a single intratracheal dose of Ni3S2 displayed an LD50 of 4 mg/kg. A lifetime study was then initiated using five graded doses of Ni3S2 or saline alone, administered once a week for 4 weeks. Animals which survived more than 60 days after the final dose were evaluated by histopathology. The study was terminated 27 months after initiation when approximately 50% of the control animals had died. There was no increase in neoplastic or nonneoplastic lesions observed in animals treated with Ni3S2 nor was there evidence of damage to the organs of the respiratory tract from this treatment. The lack of significant biological response appears to be the result of relatively low tolerated dose, efficient lung clearance, and repair of early lung lesions. | ||||||||
| 6892 | 3.30 | 16789052 | 2007.05.23 | + | Water-soluble dendrimeric two-photon tracers for in vivo imaging. | Angew Chem Int Ed Engl | ||
| TR Krishna, M Parent, MH Werts, L Moreaux, S Gmouh, S Charpak, AM Caminade, JP Majoral, M Blanchard-Desce, | ||||||||
| 6893 | 3.30 | 16735054 | 2007.01.10 | + | + | Reductive dechlorination of 1,2,4-trichlorobenzene with palladized nanoscale Fe(zero-valent) particles supported on chitosan and silica. | Chemosphere | |
| BW Zhu, TT Lim, J Feng, | ||||||||
| In this study, nanoscale Pd-Fe particles, with diameters less than 100 nm, were synthesized and dispersed over the chitosan and silica supports. Three different Pd-Fe particles were synthesized, namely 0.1% Pd-Fe, 0.5% Pd-Fe and 1.0% Pd-Fe. SEM images confirmed that the Pd-Fe particles were dispersed over the surface of the supports while SEM-EDX confirmed evenly distribution of Pd over Fe(zero-valent). alpha-Fe(zero-valent) crystallites were identified by means of XRD and observed in TEM. Reductive dechlorinations of 1,2,4-trichlorobenzene (1,2,4-TCB) with the nanoscale Pd-Fe/chitosan and Pd-Fe/silica were carried out in the batch experiment system. Disappearance of the parent species and formation of the reaction intermediates and end product were monitored at discrete times. The results show that the nano-scale Pd-Fe particles were able to completely dechlorinate the chlorinated benzenes within a very short timescale. Complete dechlorinations of 1,2,4-TCB to benzene were achieved within 60 min with the 1.0% Pd-Fe/chitosan and within 100 min with the 1.0% Pd-Fe/silica. Reaction rates were observed to increase with increasing Pd content of the Pd-Fe/support. The reactions apparently followed pseudo-first-order kinetics with respect to the 1,2,4-TCB transformation. A kinetic model is constructed to fit the experimental results for the reactions, enabling identification of the major and minor dechlorination pathways of 1,2,4-TCB. The model suggests that the 1,2,4-TCB transformation mainly followed the primary pathway of direct reductive dechlorination to benzene and secondary pathway of sequential hydrogenolysis to 1,2-dichlorobenzene (1,2-DCB) and then chlorobenzene (CB) or benzene. | ||||||||
| 6894 | 3.30 | 18514214 | 2008.09.04 | + | + | Polyacrylic acid coating of highly luminescent CdS nanocrystals for biological labeling applications. | J Colloid Interface Sci | |
| K Sato, Y Tachibana, S Hattori, T Chiba, S Kuwabata, | ||||||||
| Surface coating of highly luminescent CdS nanocrystals by polyacrylic acid was demonstrated. The method proceeded in 2 steps, (i) modification of the CdS surface by alkyl molecules and (ii) polyacrylic acid coating of the surface modified CdS. Attachment of alkyl ammonium on the CdS surface induced a phase transfer reaction from an aqueous to a non-polar phase with a yield of approximately 100%. Investigating alkyl molecules with various functional groups revealed that the alkyl molecules, possessing the cation moiety, such as amine or ammonium salt, can electrostatically interact with the CdS surface. The PL of the uncoated nanocrystals was almost entirely quenched in the pH range of approximately 7, while the polyacrylic acid coated nanocrystals exhibited moderate PL intensity. This PL intensity was preserved for at least several days, facilitating biological labeling application under a neutral condition. | ||||||||
| 6895 | 3.30 | 15046367 | 2004.06.24 | + | + | Engineered polymeric nanoparticles for soil remediation. | Environ Sci Technol | |
| W Tungittiplakorn, LW Lion, C Cohen, JY Kim, | ||||||||
| Hydrophobic organic groundwater contaminants, such as polynuclear aromatic hydrocarbons (PAHs), sorb strongly to soils and are difficult to remove. We report here on the synthesis of amphiphilic polyurethane (APU) nanoparticles for use in remediation of soil contaminated with PAHs. The particles are made of polyurethane acrylate anionomer (UAA) or poly(ethylene glycol)-modified urethane acrylate (PMUA) precursor chains that can be emulsified and cross-linked in water. The resulting particles are of colloidal size (17-97 nm as measured by dynamic light scattering). APU particles have the ability to enhance PAH desorption and transport in a manner comparable to that of surfactant micelles, but unlike the surface-active components of micelles, the individual cross-linked precursor chains in APU particles are not free to sorb to the soil surface. Thus, the APU particles are stable independent of their concentration in the aqueous phase. In this paper we show that APU particles can be engineered to achieve desired properties. Our experimental results show that the APU particles can be designed to have hydrophobic interior regions that confer a high affinity for phenanthrene (PHEN) and hydrophilic surfaces that promote particle mobility in soil. The affinity of APU particles for contaminants such as PHEN can be controlled by changing the size of the hydrophobic segment used in the chain synthesis. The mobility of colloidal APU suspensions in soil is controlled by the charge density or the size of the pendent water-soluble chains that reside on the particle surface. Exemplary results are provided illustrating the influence of alternative APU particle formulations with respect to their efficacy for contaminant removal. The ability to control particle properties offers the potential to produce different nanoparticles optimized for varying contaminant types and soil conditions. | ||||||||
| 6896 | 3.30 | 17055675 | 2007.04.05 | + | + | Application of ascorbic acid 2-glucoside as a solubilizing agent for clarithromycin: solubilization and nanoparticle formation. | Int J Pharm | |
| Y Inoue, S Yoshimura, Y Tozuka, K Moribe, T Kumamoto, T Ishikawa, K Yamamoto, | ||||||||
| Clarithromycin (CAM) was co-ground with l-ascorbic acid 2-glucoside (AA-2G), a newly developed food additive, to improve the solubility characteristics. The complete solubilizing effect of AA-2G was observed for the ground mixture with 1:1 molar ratio. When ground mixtures of CAM and AA-2G (2:1) were dispersed into water, not only the solubilization of CAM was observed but also nanoparticle formation with a mean particle diameter of 280 nm. The CAM particles obtained in this manner were stable in suspension for at least 7 days. Zeta potential analysis showed that positive charges on the particle surface may be contributing to the stability of the suspension. 1H NMR spectrum of CAM dissolved in a phosphate buffer (pH 5.5) showed a signal derived from the N,N-dimethylamino group at 2.73 ppm, while that of an equimolar ground mixture of CAM with AA-2G in D2O (pH 5.5) showed clearly two signals at 2.65 and 2.77 ppm derived from the splitting of the two methyl groups. The 13C NMR spectrum of the equimolar ground mixture dissolved in D2O exhibited two signals derived from N,N-dimethyl carbons of desosamine group at 37.2 and 42.3 ppm, whereas unprocessed CAM showed no resonance signal arising from those carbons. Moreover, the carbon resonance at 163 and 173 ppm arising from the ketone group in the CAM lactone ring shifted downfield to 177 and 180 ppm after the co-grinding with AA-2G. The formation of nanoparticles was only observed when CAM was co-ground with AA-2G in the molar ratio of 2:1, which might be attributable to a grinding-induced interaction in the solid-state via the ketone group in lactone ring of CAM. | ||||||||
| 6897 | 3.30 | 15571360 | 2006.07.26 | + | + | Intracellular pH sensors based on surface-enhanced raman scattering. | Anal Chem | |
| CE Talley, L Jusinski, CW Hollars, SM Lane, T Huser, | ||||||||
| We present the development of nanoscale pH sensors based on functionalized silver nanoparticles and surface-enhanced Raman scattering (SERS). The SERS spectrum from individual silver nanoparticle (50-80 nm in diameter) clusters functionalized with 4-mercaptobenzoic acid shows a characteristic response to the pH of the surrounding solution and is sensitive to pH changes in the range of 6-8. Measurements from nanoparticles incorporated in living Chinese hamster ovary cells demonstrate that the nanoparticle sensors retain their robust signal and sensitivity to pH when incorporated into a cell. | ||||||||
| 6898 | 3.29 | 17614579 | 2007.08.30 | + | + | Time-dependent picture of the charge-transfer contributions to surface enhanced Raman spectroscopy. | J Chem Phys | |
| JR Lombardi, RL Birke, | ||||||||
| We reexamine the Herzberg-Teller theory of charge-transfer contributions to the theory of surface enhanced Raman scattering (SERS). In previous work, the Kramers-Heisenberg-Dirac framework was utilized to explain many of the observed features in SERS. However, recent experimental and theoretical developments suggest that we revise the theory to take advantage of the time-dependent picture of Raman scattering. Results are obtained for molecular adsorption on nanoparticles in both the strong confinement limit and the weak confinement limit. We show that the Herzberg-Teller contributions to the charge-transfer effect in SERS display a resonance at the molecule-to-metal or metal-to-molecule transition while retaining the selection rules associated with normal Raman spectroscopy (i.e., harmonic oscillator, as opposed to Franck-Condon overlaps). The charge-transfer contribution to the enhancement factor scales as Gamma(-4), where Gamma is the homogeneous linewidth of the charge-transfer transition, and thus is extremely sensitive to the magnitude of this parameter. We show that the Herzberg-Teller coupling term may be associated with the polaron-coupling constant of the surface phonon-electron interaction. A time-dependent expression for the Raman amplitude is developed, and we discuss the implications of these results for both metal and semiconductor nanoparticle surfaces. | ||||||||
| 6899 | 3.29 | 17252816 | 2007.03.29 | + | + | Heterogeneity analysis of single-walled carbon nanotubes from the adsorption equilibria of nitrogen and benzene. | J Nanosci Nanotechnol | |
| WG Shim, HC Kang, C Kim, JW Lee, SC Kim, CJ Lee, H Moon, | ||||||||
| Nitrogen adsorption/desorption isotherms and gravimetric methods were employed to examine the structural and adsorption properties of selected adsorbent. The equilibrium data of benzene were also obtained at three different temperatures (303.15, 313.15, and 323.15 K) with pressures up to 7 kPa. The results of nitrogen and benzene sorption isotherm revealed that SWCNTs exhibit type II with the features of type I. The Toth and UNILAN models were found to provide a reasonable correlation between the adsorption isotherm data. In addition, the adsorption second virial coefficient and the isosteric heat of adsorption were determined by using these isotherm models. The isosteric heat of adsorption and adsorption energy distribution indicated that SWCNTs have energetically and structurally heterogeneous surfaces. | ||||||||
| 6900 | 3.29 | 17969216 | 2008.03.25 | + | + | Probing hydroxyl radicals and their imaging in living cells by use of FAM-DNA-Au nanoparticles. | Chemistry | |
| B Tang, N Zhang, Z Chen, K Xu, L Zhuo, L An, G Yang, | ||||||||
| The incorporation of gold nanoparticles (Au NPs) as quencher modules in fluorescent probes for DNA damage caused by intracellular hydroxyl radicals (HO*) is reported. Au NPs of 15 nm diameter were decorated with DNA oligomers terminating in thiol functions in their 3' positions and possessing 5' fluorophore modifications. The Au NPs, which have high extinction coefficients, functioned as excellent fluorescent quenchers in the fluorophore-Au NP composites. FRET is switched off as a factor of HO*-induced strand breakage in the single-stranded DNAs, restoring the fluorescence of the quenched fluorophores, which can be followed by spectrofluorimetry. In vitro assays with HO*-generating Fenton reagent demonstrated increases in fluorescence intensity with a linear range from 8.0 nM to 1.0 microM and a detection limit as low as 2.4 nM. Confocal microscopic imaging of macrophages and HepG2 revealed that the probe is cell-permeable and intracellular HO*-responsive. The unique combination of good selectivity and high sensitivity establishes the potential value of the probe for facilitating investigations of HO*-mediated cellular homeostasis and injury. | ||||||||
| 6901 | 3.29 | 12657748 | 2003.12.05 | + | + | Genotoxicity of samples of nickel refinery dust. | Toxicol Sci | |
| F Clemens, JR Landolph, | ||||||||
| At the International Nickel Company (INCO) nickel refinery in Clydach, Wales, U.K., which has operated since 1901, 365 respiratory cancers, including 85 nasal cancers and 280 lung cancers, have occurred in workers since the 1920s. From 1901 to 1923, incidences of these cancers were high. In 1923, the refining process was changed, eliminating a nickel arsenide, Ni5As2, called orcelite, from the refinery. Incidences of respiratory cancers decreased substantially from 1925 to 1930. Refinery dust samples were obtained in 1920 and in 1929; both of these samples contain primarily nickel oxide (NiO), but the 1920 sample also contains orcelite. The orcelite content of the 1920 sample is approximately 10%, while that of the 1929 sample is approximately 1%. We hypothesized that orcelite in the 1920 sample was partially responsible for inducing nasal and lung cancers in the refinery workers, and we tested this hypothesis. The 1920 and 1929 samples and orcelite were phagocytosed by cultured C3H/10T1/2 Cl 8 (10T1/2) mouse embryo cells to similar extents and were similarly cytotoxic to 10T1/2 cells. The 1920 sample and orcelite induced dose-dependent morphological transformation of 10T1/2 cells; the 1929 sample did not. The cell transforming ability of the 1920 sample, and therefore its probable carcinogenicity, correlates with induction of respiratory cancers in refinery workers exposed to orcelite-containing nickel refinery dust before 1923. Inability of the 1929 sample to induce morphological transformation correlates with decreased human respiratory tumor incidence at this plant after 1923. This data supports our hypothesis that orcelite in the 1920 refinery sample contributed to its carcinogenicity to nickel refinery workers. | ||||||||
| 6902 | 3.29 | 11896302 | 2002.06.21 | + | + | Acute and subchronic mammalian toxicity of naphthenic acids from oil sands tailings. | Toxicol Sci | |
| VV Rogers, M Wickstrom, K Liber, MD MacKinnon, | ||||||||
| Naphthenic acids are the most significant environmental contaminants resulting from petroleum extraction from oil sands deposits. In this study, a mixture of naphthenic acids isolated from Athabasca oil sands (AOS) tailings pond water was used in acute and subchronic toxicity tests with rodents, in order to assess potential risks posed to terrestrial wildlife. Dosages were chosen to bracket worst-case environmental exposure scenarios. In acute tests, adult female Wistar rats were given single po dosages of naphthenic acids at either 3, 30, or 300 mg per kg body weight (mg/kg), while adult male rats received 300 mg/kg. Food consumption was temporarily suppressed in the high-dose groups of both sexes. Following euthanasia 14 days later, histopathology revealed a significant incidence of pericholangitis in the high-dose group of both sexes, suggesting hepatotoxicity as an acute effect. Other histological lesions included brain hemorrhage in high-dose males, and cardiac periarteriolar necrosis and fibrosis in female rats. In subchronic tests, naphthenic acids were po administered to female Wistar rats at 0.6, 6, or 60 mg/kg, 5 days per week for 90 days. Results again suggested the liver as a potential target organ. The relative liver weight in the high-dose group was 35% higher than in controls. Biochemical analysis revealed elevated blood amylase (30% above controls) and hypocholesterolemia (43% below controls) in high-dose rats. Excessive hepatic glycogen accumulation was observed in 42% of animals in this group. These results indicate that, under worst-case exposure conditions, acute toxicity is unlikely in wild mammals exposed to naphthenic acids in AOS tailings pond water, but repeated exposure may have adverse health effects. | ||||||||
| 6903 | 3.28 | 16822222 | 2006.12.12 | + | + | The performance of nanocarriers for transmucosal drug delivery. | Expert Opin Drug Deliv | |
| N Csaba, M Garcia-Fuentes, MJ Alonso, | ||||||||
| Most of the newly designed drug molecules are characterised by low solubility in aqueous medium, low permeability through biological membranes and/or an insufficient stability in the biological environment. Fundamental studies have provided proof-of-concept of the potential of particulate nanocarriers for overcoming these unsuitable properties. For example, it is known that polymeric nanosystems may enhance transmucosal transport of drugs with poor penetration capacities while preserving their biological activity. Moreover, in recent years it has become clear that through an appropriate selection of the nanosystem components it is possible to enhance its affinity for the mucosa and, hence, the residence time of the drug in contact with the absorptive epithelium. These properties, combined with a suitably tailored release profile can markedly increase the efficacy of pharmaceuticals. Overall, the properties that have been identified as critical for the performance of these delivery systems are particle size, surface charge and surface chemical composition. These properties are known to affect the physical and chemical stability of the nanoparticles in the biological environment as well as their ability to interact (unspecific bioadhesion, receptor-mediated interaction and so on) and, eventually, overcome biological barriers. The present article aims to critically review the latest advances in this area and to provide some insights into these complex issues. Thus, herein the most widely investigated transmucosal drug delivery nanosystems and their most promising applications are reported. | ||||||||
| 6904 | 3.28 | 18575767 | 2008.09.08 | + | + | Enhancement of arsenic trioxide-induced apoptosis in HeLa cells by diethyldithiocarbamate or buthionine sulfoximine. | Int J Oncol | |
| YH Han, SZ Kim, SH Kim, WH Park, | ||||||||
| Arsenic trioxide (ATO) affects many biological functions such as cell proliferation, apoptosis, differentiation and angiogenesis in various cells. We investigated the in vitro effects of ATO as a reactive oxygen species (ROS) generator or a glutathione (GSH) depletor on apoptosis in HeLa cells. ATO decreased the viability of HeLa cells in a dose-dependent manner with an IC50 of approximately 5-6 microM. ATO triggered apoptosis, which is accompanied by the loss of mitochondrial transmembrane potential (DeltaPsim). Intracellular general ROS levels in HeLa cells were increased or decreased depending on the concentration of ATO. Particularly, the levels of O2.- were increased by ATO. In addition, we detected a decreased GSH content in ATO-treated cells. The GSH-depleted cells mainly showed propidium iodine-positive staining, indicating that the majority of the cells were dead. Diethyldithiocarbamate (DDC; an inhibitor of Cu,Zn-SOD) induced apoptosis and the loss of mitochondrial transmembrane potential (DeltaPsim) in HeLa control cells. DDC intensified apoptosis, the loss of mitochondrial transmembrane potential, increased levels of O2.- and GSH depletion in ATO-treated cells. L-buthionine sulfoximine (BSO; an inhibitor of GSH synthesis) did not induce apoptosis in HeLa control cells, but increased levels of apoptosis, O2.- and GSH depletion in ATO-treated cells. In conclusion, the changes in intracellular GSH levels rather than ROS levels are tightly related to the enhancement of ATO-induced apoptosis in HeLa cells by DDC or BSO. | ||||||||
| 6905 | 3.28 | 12862421 | 2004.03.26 | + | + | High transfection efficiency of poly(4-vinylimidazole) as a new gene carrier. | Bioconjug Chem | |
| JE Ihm, KO Han, IK Han, KD Ahn, DK Han, CS Cho, | ||||||||
| Poly(4-vinylimidazole) (P4V) was obtained by free radical polymerization of 4-vinylimidazole (4V) prepared by decarboxylation of urocanic acid. P4V formed a complex with DNA that exhibited higher transfection effiency on Hela cells than polyethylenimine (PEI), through the proton sponge mechanism of the imidazole groups in the side chain of the P4V, and low cell toxicity. | ||||||||
| 6906 | 3.28 | 14499193 | 2004.04.26 | + | + | In vitro and in vivo evaluation of the effects of PLA microparticle crystallinity on cellular response. | J Control Release | |
| DL Biggs, CS Lengsfeld, BM Hybertson, KY Ng, MC Manning, TW Randolph, | ||||||||
| Previous research suggests that crystallinity of poly(L-lactide) P(L)LA microparticles can influence surface free energy, which in turn might influence biocompatibility. This work studies the cellular response to P(L)LA microparticles of different crystallinity both in vitro and in vivo. Following incubation with P(L)LA microparticles, the in vitro production of reactive oxygen intermediates (ROI) was measured as a marker of cellular response. In both fluorescence and chemiluminescence experiments to measure ROI, a small effect of microparticle crystallinity on NR8383 AM response was observed. Microparticles of higher crystallinity elicited a smaller inflammatory response compared to lower crystallinity particles. Compared to the elevated inflammatory response induced by zymosan, the response to all P(L)LA microparticles tested was practically negligible. Results from in vivo experiments further supported conclusions that P(L)LA microparticles elicit minimal inflammatory response. Following acute exposure to P(L)LA microparticles in guinea-pig lungs, the inflammatory response was not significantly different from the response observed when sterile saline was administered. In contrast to the in vitro experiments, there were not apparent differences in cellular responses to microparticles of different crystallinity. | ||||||||
| 6907 | 3.28 | 16639883 | 2006.05.09 | + | + | Evaluation of criteria used to assess the quality of aquatic toxicity data. | Integr Environ Assess Manag | |
| DA Hobbs, MS Warne, SJ Markich, | ||||||||
| Good quality toxicity data underpins robust hazard and risk assessments in aquatic systems and the derivation of water quality guidelines for ecosystems. Hence, an objective scheme to assess the quality of toxicity data forms an important part of this process. The variation of scores from 2 research papers using the Australasian ecotoxicity database (AED) quality assessment scheme was evaluated by 23 ecotoxicologists. The results showed that the quality class that the assessors gave each paper varied by less than 10% when compared with a quality score agreed a priori between the authors of this study. It was determined that the majority of the variation in each assessment was due to ambiguous or poorly written assessment criteria, information that was difficult to find, or information in the paper that was overlooked by the assessor. This led to refinements of the assessment criteria in the AED, which resulted in a 16% improvement (i.e., reduction) in the mean variation of scores for the 2 papers when compared with the a priori scores. The improvement in consensus among different assessors evaluating the same research papers suggests that the data quality assessment scheme proposed in this article provides a more robust scheme for assessing the quality of aquatic toxicity data than methods currently available. | ||||||||
| 6908 | 3.28 | 16308207 | 2006.03.15 | + | + | Doxorubicin loaded pH-sensitive micelle targeting acidic extracellular pH of human ovarian A2780 tumor in mice. | J Drug Target | |
| ZG Gao, DH Lee, DI Kim, YH Bae, | ||||||||
| The purpose of this study was to examine the efficacy of a chemotherapeutic drug, doxorubicin (DOX), loaded in pH-sensitive micelles poly(l-histidine) (M(n):5K)-b-PEG (M(n):5K) micelles. The micelles were designed to target the acidic extracellular pH of solid tumors. Studies of pH-dependent cytotoxicity, growth rate of the tumor, pharmacokinetics and biodistribution were conducted. In vitro DOX uptake upon A2780 cells by incubating the cells in a pH 6.8 complete medium at a concentration of 20 microg DOX/ml in the micelle formulation was more than five times that of pH 7.4 condition for initial 20 min. In vivo pharmacokinetic data showed that AUC (area under concentration curve) and half life time (t(1/2)) (plasma half life) of DOX in the pH sensitive micelles increased about 5.8- and 5.2-fold of free DOX in phosphate buffered saline (PBS), respectively. It appeared that DOX in the pH-sensitive micelles preferentially accumulated in the tumor site. The distributions at 12 h post injection in other organs including liver, kidney, spleen, lung and heart were not significantly different from those of DOX in PBS at a 6 mg DOX/kg dose. The in vivo test of anti-tumor activity was performed with human ovarian carcinoma A2780 which was subcutaneously xenografted in female nu/nu athymic mice. The pH-sensitive micelle formulation significantly retarded tumor growth rate without serious body weight loss. The triggered drug release by the reduced tumor pH is believed to be a major mechanism of the observed efficacy after passive accumulation of the micelles by EPR effect. This may have resulted in a local high dose of drug in the tested solid tumor. | ||||||||
| 6909 | 3.28 | 15683652 | 2005.08.01 | + | + | Scaffold fabrication by indirect three-dimensional printing. | Biomaterials | |
| M Lee, JC Dunn, BM Wu, | ||||||||
| Three-dimensional printing (3DP) has been employed to fabricate porous scaffolds by inkjet printing liquid binder droplets onto particulate matter. Direct 3DP, where the final scaffold materials are utilized during the actual 3DP process, imposes several limitations on the final scaffold structure. This study describes an indirect 3DP protocol, where molds are printed and the final materials are cast into the mold cavity to overcome the limitations of the direct technique. To evaluate the resolution available in this technique, scaffolds with villi features (500 microm diameter, 1 mm height) were produced by solvent casting into plaster molds, followed by particulate leaching. Scanning electron microscope (SEM) showed highly open, well interconnected, uniform pore architecture ( approximately 100-150 microm). The ability of these scaffolds to support intestinal epithelial cell (IEC6) culture was investigated in vitro. IEC6 cells attached to scaffolds uniformly in vitro and grew preferentially in the villi region. To exploit the freeform nature of this technique with large pore size, anatomically shaped zygoma scaffolds with 300-500 microm interconnected pores were produced and characterized. Indirect 3DP provides an alternative method to complement other direct solid freeform fabrication methods. | ||||||||
| 6910 | 3.28 | 14729366 | 2004.03.04 | + | + | Comet assay and micronucleus test in circulating erythrocytes of Cyprinus carpio specimens exposed in situ to lake waters treated with disinfectants for potabilization. | Mutat Res | |
| A Buschini, A Martino, B Gustavino, M Monfrinotti, P Poli, C Rossi, M Santoro, AJ Dörr, M Rizzoni, | ||||||||
| The detection of a possible genotoxic effect of surface water treated with disinfectants for potabilization is the aim of the present work. The Comet assay and the micronucleus test were applied in circulating erythrocytes of Cyprinus carpio. Young specimens (20-30 g) were exposed in experimental basins, built within the potabilization plant of Castiglione del Lago (Perugia, Italy). In this plant the water of the Trasimeno Lake is treated and disinfected for potabilization before it is distributed to the people in the net of drinkable water. A continuous flow of water at a constant rate was supplied to basins; the water was continuously treated at a constant concentration with one of the three tested disinfectants (sodium hypochlorite, peracetic acid and chloride dioxide), one control basin being supplied with untreated water. Three sampling campaigns were performed: October 2000, February 2001 and June 2001. Repeated blood samplings through intracardiac punctures allowed to follow the same fish populations after different exposure times: before introduction of the disinfectant, and 10 or 20 days afterwards. An additional blood sampling was performed 3 h after addition of the disinfectant in other, simultaneously exposed, fish populations. Genotoxic damage was shown in fish exposed to water disinfected with sodium hypochlorite and chloride dioxide. The Comet assay showed an immediate response, i.e. DNA damage that was induced directly in circulating erythrocytes, whereas micronuclei reached their highest frequencies at later sampling times, when a genotoxic damage in stem cells of the cephalic kidney is expressed in circulating erythrocytes. The quality of the untreated surface water seems to be the most important parameter for the long-term DNA damage in circulating erythrocytes. | ||||||||
| 6911 | 3.28 | 16471522 | 2006.08.21 | + | + | One-pot synthesis of hollow Au3Cu1 spherical-like and biomineral botallackite Cu2(OH)3Cl flowerlike architectures exhibiting antimicrobial activity. | J Phys Chem B | |
| MT Hsiao, SF Chen, DB Shieh, CS Yeh, | ||||||||
| A new form of Au3Cu1 hollow nanostructure was prepared by the reaction of Cu nanoparticles with HAuCl4. Following a course of aging, the biomineral botallackite Cu2(OH)3Cl nanoflowers were developed with the aid of Au3Cu1 hollow nanostructures at room temperature. It was proposed that the hollow nanospheres could serve as active centers for heterogeneous nucleation and mediated a mineralization process. Scanning electron microscopy and high-resolution transmission electron microscopy indicated that the nanoflowers are three-dimensional in appearance with a range of 500 nm-- to 1 microm in size and made of several nanopetals with about 25 nm in thickness. In addition, we found that the shape separation could be achieved by using cationic cetyltrimethylammonium bromide to filter the different morphology spherical- and flowerlike structures due to the negative charge of hollow nanospheres. Both hollow nanospheres and nanoflowers presented antimicrobial activity toward Streptococcus aureus with MIC50 at 39.6 and 127.2 microg/mL, respectively. | ||||||||
| 6912 | 3.27 | 17437067 | 2007.10.19 | + | + | Novel fabrication of a polymer scaffold with a dense bioactive ceramic coating layer. | J Mater Sci Mater Med | |
| IK Jun, YH Koh, SH Lee, HE Kim, | ||||||||
| A novel method of coating a polymeric scaffold with a dense ceramic layer was developed. This method exploits the fact that only one of the two interlaced 3-D channels formed in a ceramic dual-scaffold can be infiltrated with a polymer. Firstly, a 3-D graphite network prepared by the rapid prototyping (RP) method was dip-coated with hydroxyapatite (HA) slurry, followed by heat-treatment at 1250 degrees C for 3 h in air. This created an additional 3-D channel through the removal of the graphite network, while preserving the pre-existing 3-D channel. Thereafter, only one channel was infiltrated with a molten poly(epsilon-caprolactone) (PCL) polymer at 140 degrees C for 12 h, producing a PCL scaffold with a dense, uniform HA coating layer. The sample showed high compressive strength with ductile behavior, due to the nature of the PCL polymer, and an excellent cellular response afforded by the bioactive HA coating layer. The results indicate that this novel technique provides a highly versatile method of coating various polymeric scaffolds with bioactive layers in order to endow them with advanced functionalities. | ||||||||
| 6913 | 3.27 | 14503403 | 2004.04.30 | + | + | Nano-octopus: a new form of branching carbon nanofiber. | J Nanosci Nanotechnol | |
| D Pradhan, M Sharon, M Kumar, Y Ando, | ||||||||
| A new multibranched octopus-type structure of carbon nanofibers is synthesized from a natural precursor, camphor, by a thermal chemical vapor deposition technique. An alloy of Cu:Ni catalyst is prepared by electrochemically coating nickel on a copper sheet, with nickel sulfate as an electrolyte, and heating that nickel-coated copper sheet to a higher temperature. Deposition of carbon on these substrates leads to the formation of a branched nanostructure in the temperature range of 923 K to 1023 K. The fiber diameter increases from 30 nm to 250 nm with increasing pyrolysis temperature. Detailed morphology and the internal structure of these fibers are studied by scanning and transmission electron microscopy. | ||||||||
| 6914 | 3.27 | 15681092 | 2005.06.24 | + | + | PEG shielded polymeric double-layered micelles for gene delivery. | J Control Release | |
| AM Funhoff, S Monge, R Teeuwen, GA Koning, NM Schuurmans-Nieuwenbroek, DJ Crommelin, DM Haddleton, WE Hennink, CF van Nostrum, | ||||||||
| A combination of A-B and B-C block copolymers was used to encapsulate DNA inside pEG coated particles, where A is a cationic block (poly(dimethylaminoethyl methacrylate), pDMAEMA) for DNA binding and condensation, B is a hydrophobic block (poly(butylmethacrylate), pBMA) and C is a polyethylene glycol (pEG) block. The AB and BC block copolymers were synthesized by transition metal mediated radical polymerization. The AB block copolymer had a fixed pBMA molecular weight of 3800 g/mol and a varying pDMAEMA molecular weight (from 22 to 65 kg/mol), the BC block copolymer had a fixed composition (pBMA 9000 g/mol; pEG 2000 g/mol). Plasmid DNA containing particles were made via a detergent dialysis method. By this method, particles of approximately 120 nm, as determined by dynamic light scattering (DLS), with a near neutral charge were formed, independent of the DMAEMA block size. DLS measurements and gel electrophoresis indicated that the particles were very stable in cell culture medium at 37 degrees C and resistant to anionic exchange by poly-l-aspartic acid. The particles were able to transfect COS-7 and OVCAR-3 cells with minor toxicity if incubated for 1 or 4 h; incubation for 24 h resulted in an increased toxicity. This paper shows that small polyplexes with near neutral charge can be obtained via a convenient detergent dialysis method using pDMAEMA-b-pBMA and pBMA-b-pEG. These particles may be interesting for in vivo experiments where particles with high positive charges have adverse interactions with blood components. | ||||||||
| 6915 | 3.27 | 18596351 | 2008.07.29 | + | + | Fluorescent silica nanoparticles. | Ann N Y Acad Sci | |
| H Mader, X Li, S Saleh, M Link, P Kele, OS Wolfbeis, | ||||||||
| We report on the preparation of fluorescent silica nanoparticles (NPs). They have been prepared by (a) modification of the NPs by amino groups and subsequent introduction of amino-reactive fluorophores of various color and (b) by modification of the NPs by either azido groups or alkyne groups and subsequent conjugation to fluorophores by so-called click chemistry, which is a novel approach toward modifying silica NPs. The new NPs were characterized in terms of size and spectral properties. | ||||||||
| 6916 | 3.27 | 17380262 | 2007.09.04 | + | + | Ionically fixed polymeric nanoparticles as a novel drug carrier. | Pharm Res | |
| SW Lee, DH Chang, MS Shim, BO Kim, SO Kim, MH Seo, | ||||||||
| PURPOSE: In this study, we have prepared a novel polymeric drug delivery system comprised of ionically fixed polymeric nanoparticles (IFPN) and investigated their potential as a drug carrier for the passive targeting of water-insoluble anticancer drugs. MATERIALS AND METHODS: For this purpose, the physicochemical characteristics of the IFPN were investigated by comparing them with conventional polymeric micelles. IFPN containing paclitaxel were prepared and evaluated for in vitro stability and in vivo pharmacokinetics. RESULTS: The IFPN were successfully fabricated using a monomethoxypolyethylene glycol-polylactide (mPEG-PLA) diblock copolymer and a sodium salt of D,L-poly(lactic acid) (D,L-PLACOONa) upon the addition of CaCl2. The transmittance of the IFPN solution was much lower than that of a polymeric micelle solution at the same polymer concentration implicating an increase in the number of appreciable particles. The particle size of the IFPN was approximately 20 approximately 30 nm which is in the range of particle sizes that facilitate sterile filtration using a membrane filter. The IFPN also have a regular spherical shape with a narrow size distribution. The zeta potential of the IFPN was almost neutral, similar to that of the polymeric micelles. In contrast, mixed micelles with a combination of mPEG-PLA and D,L-PLACOONa prior to the addition of Ca2+ showed a negative charge (-17 mV), possibly due to the carboxyl anion of polylactic acid exposed on the surface of the micelles. The IFPN formulation was highly kinetically stable in aqueous medium compared to the polymeric micelle formulation. The molecular weight of D,L-PLACOONa in the IFPN and the mPEG-PLA/D,L-PLACOONa molar ratio had a great influence upon the kinetic stability of the IFPN. Pharmacokinetic studies showed that the area under the concentration vs time curve (AUC) of IFPN in blood was statistically higher (about two times) when compared with that of Cremophor EL-based formulation (Taxol equivalent) or polymeric micelle formulation. CONCLUSIONS: The results suggests that the IFPN were retained in the circulation long enough to play a significant role as a drug carrier in the bloodstream, possibly resulting in improved therapeutic efficiency. Therefore, the IFPN are expected to be a promising novel polymeric nanoparticulate system for passive tumor targeting of water-insoluble anticancer drugs including paclitaxel. | ||||||||
| 6917 | 3.27 | 18678008 | 2008.10.09 | + | + | Interactions of hydrophobic fractions of dissolved organic matter with Fe(3+) - and Cu(2+)-montmorillonite. | Environ Sci Technol | |
| T Polubesova, Y Chen, R Navon, B Chefetz, | ||||||||
| Interactions of dissolved organic matter (DOM) with clays can significantly affect a variety of soil processes. We studied adsorption and fractionation of hydrophobic acid (HoA) and hydrophobic neutral (HoN) fractions of DOM on Cu(2+)- and Fe(3+)-montmorillonite. Adsorption of both samples was higher on Fe(3+)-montmorillonite than on Cu(2+)-montmorillonite. A pH increase of about one unit was recorded followed by HoA adsorption by Fe(3+)-montmorillonite. This suggested exchange of negatively charged DOM groups on surface hydroxyl groups of Fe(3+)-montmorillonite surfaces. Adsorption of HoA on Cu(2+)-montmorillonite and HoN on Fe(3+)- and Cu(2+)-montmorillonites was governed mainly by van der Waals interactions. Spectroscopic analyses showed a distinct HoA fractionation by molecular size and aromaticity only by Fe(3+)-montmorillonite. On the basis of the pH measurements (increase in pH following adsorption of acid components) and enhanced DOM fractionation by molecular size and aromaticity we suggest that DOM reacted with Fe(3+)-montmorillonite similar to goethite. | ||||||||
| 6918 | 3.27 | 6927640 | 1986.11.17 | + | + | Toxicity of 29 plasticizers to HeLa cells in the MIT-24 system. | Toxicology | |
| B Ekwall, C Nordensten, L Albanus, | ||||||||
| The toxicity to HeLa cells of 29 plasticizers was determined in the MIT-24 test system. The 7-day IC50 for HeLa cells varied from 260 to 1.5 g/l. Phthalates, adipates, sebacates, azelates and phosphates with long carbon chain alcohols were very non-toxic to the cells, probably due to insolubility in water of the compounds, while the citrates, some phosphates and the 2 polymer plasticizers had a higher toxicity to the cells. A comparison of the HeLa cytotoxicity with the toxicity in vitro to other cells for 7 plasticizers showed a similarity of the cytotoxicity to all cell types. A comparison of the HeLa cytotoxicity for 20 plasticizers with i.p. lethal dosage in rodents demonstrated a rough similarity of values, suggesting a toxicity in rodents of the compounds by toxic interference of the agents with basal functions and structures of tissues (basal cytotoxicity). Tissue culture studies of the cytotoxic mechanisms of the plasticizers therefore could reveal modes of toxic action in vivo. | ||||||||
| 6919 | 3.26 | 17454250 | 2007.05.24 | + | + | Biological interactions of functionalized single-wall carbon nanotubes in human epidermal keratinocytes. | Int J Toxicol | |
| LW Zhang, L Zeng, AR Barron, NA Monteiro-Riviere, | ||||||||
| Carbon nanotube-based nanovectors, especially functionalized nanotubes, have shown potential for therapeutic drug delivery. 6-Aminohexanoic acid-derivatized single-wall carbon nanotubes (AHA-SWNTs) are soluble in aqueous stock solutions over a wide range of physiologically relevant conditions; however, their interactions with cells and their biological compatibility has not been explored. Human epidermal keratinocytes (HEKs) were dosed with AHA-SWNTs ranging in concentration from 0.00000005 to 0.05 mg/ml. MTT (3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide) cell viability decreased significantly (p < .05) from 0.00005 to 0.05 mg/ml after 24 h. The proinflammatory mediators of inflammation cytokines interleukin (IL)-6, IL-8, tumor necrosis factor (TNF)-alpha, IL-10, and IL-1beta were also assessed. Cytokine analysis did not show a significant increase in IL-6 and IL-8 in the medium containing 0.000005 mg/ml of AHA-SWNTs from 1 to 48 h. IL-6 increased in cells treated with 0.05 mg/ml of AHA-SWNTs from 1 to 48 h, whereas IL-8 showed a significant increase at 24 and 48 h. No significant difference (p < .05) was noted with TNF-alpha, IL-10, and IL-1beta expression at any time point. Transmission electron microscopy of HEKs treated with 0.05 mg/ml AHA-SWNTs for 24 h depicted AHA-SWNTs localized within intracytoplasmic vacuoles in HEKs. Treatment with the surfactant 1% Pluronic F127 caused dispersion of the AHA-SWNT aggregates in the culture medium and less toxicity. These data showed that the lower concentration of 0.000005 mg/ml of AHA-SWNTs maintains cell viability and induces a mild cytotoxicity, but 0.05 mg/ml of AHA-SWNTs demonstrated an irritation response by the increase in IL-8. | ||||||||
| 6920 | 3.26 | 18517250 | 2008.09.22 | + | + | Effect of the head-group geometry of amino acid-based cationic surfactants on interaction with plasmid DNA. | Biomacromolecules | |
| V Jadhav, S Maiti, A Dasgupta, PK Das, RS Dias, MG Miguel, B Lindman, | ||||||||
| The interaction between DNA and different types of amino acid-based cationic surfactants was investigated. Particular attention was directed to determine the extent of influence of surfactant head-group geometry toward tuning the interaction behavior of these surfactants with DNA. An overview is obtained by gel retardation assay, isothermal titration calorimetry, fluorescence spectroscopy, and circular dichroism at different mole ratios of surfactant/DNA; also, cell viability was assessed. The studies show that the surfactants with more complex/bulkier hydrophobic head group interact more strongly with DNA but exclude ethidium bromide less efficiently; thus, the accessibility of DNA to small molecules is preserved to a certain extent. The presence of more hydrophobic groups surrounding the positive amino charge also gave rise to a significantly lower cytotoxicity. The surfactant self-assembly pattern is quite different without and with DNA, illustrating the roles of electrostatic and steric effects in determining the effective shape of a surfactant molecule. | ||||||||
| 6921 | 3.26 | 17691749 | 2007.11.13 | + | + | From designer clusters to synthetic crystalline nanoassemblies. | Nano Lett | |
| AW Castleman, SN Khanna, A Sen, AC Reber, M Qian, KM Davis, SJ Peppernick, A Ugrinov, MD Merritt, | ||||||||
| Clusters have the potential to serve as building blocks of materials, enabling the tailoring of materials with novel electronic or magnetic properties. Historically, there has been a disconnect between magic clusters found in the gas phase and the synthetic assembly of cluster materials. We approach this challenge through a proposed protocol that combines gas-phase investigations to examine feasible units, theoretical investigations of energetic compositional diagrams and geometrical shapes to identify potential motifs, and synthetic chemical approaches to identify and characterize cluster assemblies in the solid state. Through this approach, we established As7(3-) as a potential stable species via gas-phase molecular beam experiments consistent with its known existence in molecular crystals with As to K ratios of 7:3. Our protocol also suggests another variant of this material. We report the synthesis of a cluster compound, As7K1.5(crypt222-K)1.5, composed of a lattice of As7 clusters stabilized by charge donation from cryptated K atoms and bound by sharing K atoms. The bond dimensions of this supercluster assembled material deduced by X-ray analysis are found to be in excellent agreement with the theoretical calculations. The new compound has a significantly larger band gap than the hitherto known solid. Thus, our approach allows the tuning of the electronic properties of solid cluster assemblies. | ||||||||
| 6922 | 3.26 | 17654994 | 2007.09.07 | + | + | Meso-patterning of thin polymer films by controlled dewetting: from nano-droplet arrays to membranes. | J Nanosci Nanotechnol | |
| R Mukherjee, M Gonuguntla, A Sharma, | ||||||||
| Controlled dewetting of thin polymer films on physically heterogeneous substrates is employed as a new soft lithography route to obtain various types of ordered meso-scale structures, including nano-membranes and ordered arrays of nano-droplets. Dewetting of a thin polymer film on a defect free homogeneous surface occurs by a randomly placed collection of holes and droplets with a well-defined spacing. In contrast, on a physically patterned surface, strong influence of the underlying pattern is observed on the dewetting pathways as well as on the ordering and size of the resulting meso-scale structures. The imposed periodicity of the substrate pattern vis-à-vis the spinodal length scale of dewetting provides a powerful tool for the morphology and size control. The thickness of the film and the kinetics of dewetting are the other important parameters that govern the morphology of the resulting structures. | ||||||||
| 6923 | 3.26 | 18477478 | 2008.06.20 | + | + | Form and dimensions of aggregates dictate cytotoxicities of Danish dementia peptides. | Biochem Biophys Res Commun | |
| I Surolia, DP Sarkar, S Sinha, | ||||||||
| Familial Danish dementia (FDD) is a neurodegenerative disease which results due to alterations in the BRI2 gene. The pathological symptoms of the disease are cerebral amyloidolysis, parenchymal protein deposits and neuronal degeneration. The ADan peptide is a 34 amino acid long peptide which is thought to be the major cause of amyloid deposition in brains of patients suffering from FDD. Due to the presence of two cysteine residues viz. cys5 and cys23, this peptide exists in two forms: a cyclic oxidized form where the two cysteines form a disulfide bridge and a linear reduced form where the sulphydryl groups of cysteine are free. The relationship between toxicity and structure of the reduced and oxidized forms of ADan peptides has been elucidated by a combination of biophysical and cellular toxicity assays. It is observed that the reduced peptide has a stronger lethal effect on neuronal cell lines compared to its oxidized counterparts at all stages of aggregation. Further, it is observed that the fresh reduced peptide induced greater cell death as compared to its aged counterpart. | ||||||||
| 6924 | 3.26 | 16701831 | 2006.06.06 | + | + | Substrate-mediated delivery from self-assembled monolayers: effect of surface ionization, hydrophilicity, and patterning. | Acta Biomater | |
| AK Pannier, BC Anderson, LD Shea, | ||||||||
| Gene transfer has many potential applications in basic and applied sciences. In vitro, DNA delivery can be enhanced by increasing the concentration of DNA in the cellular microenvironment through immobilization of DNA to a substrate that supports cell adhesion. Substrate-mediated delivery describes the immobilization of DNA, complexed with cationic lipids or polymers, to a biomaterial or substrate. As surface properties are critical to the efficiency of the surface delivery approach, self-assembled monolayers (SAMs) of alkanethiols on gold were used to correlate surface chemistry of the substrate to binding, release, and transfection of non-specifically immobilized complexes. Surface hydrophobicity and ionization were found to mediate both DNA complex immobilization and transfection, but had no effect on complex release. Additionally, SAMs were used in conjunction with soft lithographic techniques to imprint substrates with specific patterns, resulting in patterned DNA complex deposition and transfection, with transfection efficiencies in the patterns nearing 40%. Controlling the interactions between complexes and substrates, with the potential for patterned delivery, can be used to locally enhance or regulate gene transfer, with applications to tissue engineering scaffolds and transfected cell arrays. | ||||||||
| 6925 | 3.26 | 9741926 | 1998.11.30 | + | + | DNA-polycation nanospheres as non-viral gene delivery vehicles. | J Control Release | |
| KW Leong, HQ Mao, VL Truong-Le, K Roy, SM Walsh, JT August, | ||||||||
| Nanospheres synthesized by salt-induced complex coacervation of cDNA and polycations such as gelatin and chitosan were evaluated as gene delivery vehicles. DNA-nanospheres in the size range of 200-750 nm could transfect a variety of cell lines. Although the transfection efficiency of the nanospheres was typically lower than that of lipofectamine and calcium phosphate controls in cell culture, the beta-gal expression in muscle of BALB/c mice was higher and more sustained than that achieved by naked DNA and lipofectamine complexes. This gene delivery system has several attractive features: (1) ligands can be conjugated to the nanosphere for targeting or stimulating receptor-mediated endocytosis; (2) lysosomolytic agents can be incorporated to reduce degradation of the DNA in the endosomal and lysosomal compartments; (3) other bioactive agents or multiple plasmids can be co-encapsulated; (4) bioavailability of the DNA can be improved because of protection from serum nuclease degradation by the polymeric matrix; (5) the nanosphere can be lyophilized for storage without loss of bioactivity. | ||||||||
| 6926 | 3.26 | 15375176 | 2005.03.18 | + | + | {beta}-Amyloid-induced neurodegeneration and protection by structurally diverse microtubule-stabilizing agents. | J Pharmacol Exp Ther | |
| ML Michaelis, S Ansar, Y Chen, ER Reiff, KI Seyb, RH Himes, KL Audus, GI Georg, | ||||||||
| Deposition of beta-amyloid peptide (Abeta) and hyperphosphorylation of the tau protein are associated with neuronal dysfunction and cell death in Alzheimer's disease. Although the relationship between these two processes is not yet understood, studies have shown that both in vitro and in vivo exposure of neurons to Abeta leads to tau hyperphosphorylation and neuronal dystrophy. We previously reported that the microtubule-stabilizing drug paclitaxel (Taxol) protects primary neurons against toxicity induced by the Abeta(25-35) peptide. The studies in this report were undertaken to characterize the actions of paclitaxel more fully, to assess the effectiveness of structurally diverse microtubulestabilizing agents in protecting neurons, and to determine the time course of the protective effects of the drugs. Primary neurons were exposed to Abeta in the presence or absence of several agents shown to interact with microtubules, and neuronal survival was monitored. Paclitaxel protected neurons against Abeta(1-42) toxicity, and paclitaxel-treated cultures exposed to Abeta showed enhanced survival over Abeta-only cultures for several days. Neuronal apoptosis induced by Abeta was blocked by paclitaxel. Other taxanes and three structurally diverse microtubule-stabilizing compounds also significantly increased survival of Abeta-treated cultures. At concentrations below 100 nM, the drugs that protected the neurons did not produce detectable toxicity when added to the cultures alone. Although multiple mechanisms are likely to contribute to the neuronal cell death induced by oligomeric or fibrillar forms of Abeta, low concentrations of drugs that preserve the integrity of the cytoskeletal network may help neurons survive the toxic cascades initiated by these peptides. | ||||||||
| 6927 | 3.26 | 11351999 | 2001.06.14 | + | + | Biomagnification of DDT through the benthic and pelagic food webs of Lake Malawi, East Africa: importance of trophic level and carbon source. | Environ Sci Technol | |
| KA Kidd, HA Bootsma, RH Hesslein, DC Muir, RE Hecky, | ||||||||
| Lake Malawi, an East African Rift Valley lake, is internationally renowned for having the highest diversity of fish species in the world, and these cichlids are highly specialized in their dietary habits. In this lake, tissue stable carbon (delta13C) and nitrogen (delta15N) isotopes can be used over several trophic levels to distinguish those consumers relying upon carbon fixed by either benthic or pelagic primary producers. As such, it was possible to contrast the biomagnification of persistent organochlorines through the benthic and pelagic food webs. In 1996 and 1997, food-web organisms were collected from Lake Malawi and analyzed for organochlorines, delta13C and delta15N to determine the factors that affectthe biomagnification of contaminants in a tropical lake. The pesticide DDT was the most predominant pollutant in the biota from Lake Malawi and was found at the highest concentrations in the largest and fattiest fish species. As observed in temperate systems, log-transformed sigmaDDT concentrations in food-web organisms were significantly predicted by delta15N or log lipid (r2 = 0.32 and 0.40, respectively). In addition, the slope of the regression of log sigmaDDT versus delta15N was significantly higher in the pelagic than the benthic food web. These results indicate that pelagic organisms are at greater risk of accumulating these pollutants than biota relying upon benthic primary production. | ||||||||
| 6928 | 3.25 | 15225730 | 2005.04.12 | + | + | Synthesis of potent taxoids for tumor-specific delivery using monoclonal antibodies. | Bioorg Med Chem Lett | |
| ML Miller, EE Roller, X Wu, BA Leece, VS Goldmacher, RV Chari, I Ojima, | ||||||||
| The targeted delivery of taxoids, in the form of taxane-antibody immunoconjugates, requires the preparation of taxoids containing moieties suitable for their conjugation to monoclonal antibodies. A series of taxoids incorporating a disulfide-containing linker at various positions of the taxoid framework have been prepared to investigate the most suitable position for conjugation. A second series of taxoids modified at the C-2 position aimed at increasing the potency of these taxanes has also been prepared. | ||||||||
| 6929 | 3.25 | 16375355 | 2006.07.25 | + | + | Spectrophotometric study of fluorescence sensing and selective binding of biochemical substrates by 2,2'-bridged bis(beta-cyclodextrin) and its water-soluble fullerene conjugate. | J Phys Chem B | |
| Y Liu, P Liang, Y Chen, YL Zhao, F Ding, A Yu, | ||||||||
| A bis(beta-cyclodextrin)-fullerene conjugate (3) linked at the secondary hydroxyl side was prepared in a good yield from its precursor N,N'-bis(2-(2-aminoethylamino)ethyl)malonamide-bridged bis(beta-cyclodextrin) (2). Spectrophotomeric studies on the conformation and the inclusion complexation behavior of 3 with a variety of organic and biochemical substrates by means of UV-vis, FT-IR, NMR, fluorescence, and circular dichroism spectroscopy showed that the bis(beta-cyclodextrin)-fullerene conjugate displayed an intramolecular capsule-type conformation in aqueous solution. Because of the multiple binding of bis(beta-cyclodextrin) with substrates, 2 can act as an efficient fluorescence sensor for biochemical substrates, while its fullerene conjugate 3 displays a capability of cleaving DNA under visible-light irradiation. | ||||||||
| 6930 | 3.25 | 16438662 | 2006.12.20 | + | + | Optimization, application, and interpretation of lactate dehydrogenase measurements in microwell determination of cell number and toxicity. | Assay Drug Dev Technol | |
| HT Wolterbeek, AJ van der Meer, | ||||||||
| The lactate dehydrogenase (LDH) assay was addressed for its sensitivity, disturbances by foaming, and cell number and size. Cells were from a U-251 MG grade IV human glioblastoma brain tumor cell line used in 100-microl well volumes. Cells were counted by microscopy and Coulter counting; assays were LDH or trypan blue. The results indicate increased 490 nm signals (level, variance) by using phenol red or by increasing fetal bovine serum from 5% to 10%. The data also indicate that defoaming results in reduced variances ranging from a factor of 2 at 1-3 units of absorption, up to a factor of 4-5 at <1 units of absorption. Coulter counting indicated a decrease in cell volume with increasing end-point cell density, attributed to general shrinking at increasing density. In comparisons, total LDH was considered relative to both cell total volume and cell numbers. The result suggests that total LDH should be regarded as reflecting cell total volume rather than cell numbers. In a comparative Cu exposure test, signals of both LDH and a sodium salt of 4-[3-(4-iodophenyl)-2-(4-nitrophenyl)-2H-5-tetrazolio]-1,3-benzene disulfonate (WST-1) decreased with increasing Cu supply, while bromodeoxyuridine signals remained largely unaffected. The data show the differences in responses in cell viability and proliferation, but, above all, indicate that LDH should be expressed on a per cell volume basis rather than per cell, to avoid the problem that mere density effects contribute to signals on compound or metal toxicity. | ||||||||
| 6931 | 3.24 | 11498804 | 2001.09.27 | + | Toxicity of fibers and particles. Report of the workshop held in Munich, Germany, 26-27 October 2000. | Inhal Toxicol | ||
| H Greim, P Borm, R Schins, K Donaldson, K Driscoll, A Hartwig, E Kuempel, G Oberdörster, G Speit, | ||||||||
| 6932 | 3.24 | 18079013 | 2008.04.03 | + | + | Preparation and in vitro evaluation of the antiviral activity of the Acyclovir complex of a beta-cyclodextrin/poly(amidoamine) copolymer. | J Control Release | |
| M Bencini, E Ranucci, P Ferruti, F Trotta, M Donalisio, M Cornaglia, D Lembo, R Cavalli, | ||||||||
| A poly(amidoamine) (PAA) copolymer with beta-cyclodextrin was obtained by polyaddition reaction of 6-deoxy-6-amino-beta-cyclodextrin (beta-CD-NH(2)) and 2-methylpiperazine to 2,2-bis(acrylamido)acetic acid in aqueous medium. This beta-CD/PAA copolymer bears beta-CD units along the macromolecular chain, is water-soluble and non-cytotoxic. The complexing capacity of beta-CD/PAA was determined using an antiviral drug, Acyclovir, as a model of poorly water-soluble drug. Complex formation was confirmed by means of DSC and FTIR analyses. beta-CD/PAA can solubilize up to 11% w/w of Acyclovir notably increasing the aqueous solubility of the drug. The in vitro release studies showed the dependence of Acyclovir release rate on the solution pH. The antiviral activity of Acyclovir beta-CD/PAA complex was evaluated against herpes simplex virus type I in cell cultures. The Acyclovir beta-CD/PAA complex exhibited a higher antiviral activity than the free drug. | ||||||||
| 6933 | 3.24 | 17944498 | 2008.02.08 | + | + | Complex colloidal microclusters from aerosol droplets. | Langmuir | |
| YS Cho, GR Yi, YS Chung, SB Park, SM Yang, | ||||||||
| In this Article, we report on a packing scheme of monodisperse colloidal nanospheres by aerosol-assisted clustering. When an aqueous suspension of colloidal nanospheres was sprayed into aerosol droplets by an ultrasonic nebulizer, the nanospheres were encapsulated in the aerosol droplets and the evaporation of water from the droplets at high temperatures led to the packings of nanospheres. The configurations of the colloidal nanospheres minimized the interparticle potential energy or the second moment of mass distribution depending on the number of the constituting nanospheres. Other types of nonspherical microparticles or hollow microclusters were also produced by self-organizing organic-inorganic binary colloids of different sizes in an aerosol spray pyrolysis reactor. The aerosol-assisted fabrication of colloidal clusters was very effective as compared to the method based on oil-in-water or water-in-oil emulsions, in which the removal of residual oil was not easy and time-consuming. | ||||||||
| 6934 | 3.24 | 15856091 | 2005.07.11 | + | + | Multi-walled carbon nanotubes for plasmid delivery into Escherichia coli cells. | Lab Chip | |
| J Rojas-Chapana, J Troszczynska, I Firkowska, C Morsczeck, M Giersig, | ||||||||
| Introduction of foreign genes into bacterial cells (transformation) is used for supplementing defective genes or providing additional biological functions. Transformation can be achieved using either chemical or physical methods, e.g., electroporation. Bulk electroporation offers several advantages over chemical methods, including high transformation efficiency, but its application is limited due to the high numbers of cells and plasmids needed as a result of the high death rate of cells during this process, and the difficulty in electroporating single cells. Synthetic inorganic gene nanocarriers have received limited attention in the transformation of bacterial cells. Here we present a plasmid delivery system based on water dispersible multi-walled carbon nanotubes (CNTs) that can simultaneously target the bacterial surface and deliver the plasmids into the cells via temporary nanochannels across the cell envelope. Transformation experiments performed on E. coli provide evidence for the high potential of CNTs for nanoscale cell electroporation. | ||||||||
| 6935 | 3.24 | 17292111 | 2007.03.05 | + | + | Nanoencapsulation I. Methods for preparation of drug-loaded polymeric nanoparticles. | Nanomedicine | |
| C Pinto Reis, RJ Neufeld, AJ Ribeiro, F Veiga, | ||||||||
| Polymeric nanoparticles have been extensively studied as particulate carriers in the pharmaceutical and medical fields, because they show promise as drug delivery systems as a result of their controlled- and sustained-release properties, subcellular size, and biocompatibility with tissue and cells. Several methods to prepare nanoparticles have been developed during the last two decades, classified according to whether the particle formation involves a polymerization reaction or arises from a macromolecule or preformed polymer. In this review the most important preparation methods are described, especially those that make use of natural polymers. Advantages and disadvantages will be presented so as to facilitate selection of an appropriate nanoencapsulation method according to a particular application. | ||||||||
| 6936 | 3.24 | 15883675 | 2005.07.22 | + | + | Toxicity of the crude oil water-soluble fraction and kaolin-adsorbed crude oil on Daphnia magna (Crustacea: Anomopoda). | Arch Environ Contam Toxicol | |
| F Martínez-Jerónimo, R Villaseñor, G Ríos, F Espinosa-Chavez, | ||||||||
| Crude oil is a complex mixture of hydrocarbons entering aquatic environments from accidental or normal marine and transportation activities. Toxicologic crude oil analysis is usually performed on the basis of the water-soluble fraction. However, this yields only a partial estimate of the damage caused by these contaminants because a substantial hydrophobic amount can be adsorbed onto suspended solids (biotic and abiotic), which directly affects filter-feeding species and permits bioaccumulation through trophic relationships. This study determined the acute toxic damage sustained after 48 hours caused by seven types of crude oil from Tabasco, Mexico on the cladoceran Daphnia magna. Comparisons were documented based on the responses of D. magna from application of the water-soluble fraction and exposure to entire crude oil samples adsorbed on kaolin clay. Oil-sorbed kaolin was more toxic than the water-soluble fraction in acute exposure. This confirms that tests of the water-soluble fraction tend to underestimate the toxic damage that can be produced in natural environments. Furthermore, chronic toxicity (21 days) was evaluated for crude oil samples adsorbed on kaolin at sublethal concentrations as established from Application Factors (AF) criteria. Results showed that in most cases, it is impossible to predict safe concentrations on the basis of LC(50) values because samples with lower acute toxicity exercised a greater influence on D. magna reproduction and survival when subjected to chronic exposure. | ||||||||
| 6937 | 3.24 | 11915239 | 2002.04.16 | + | + | [Acute effects of methyl bromide gas in rats and mice--studies on survival time] | J UOEH | |
| H Hori, T Hyakudo, T Oyabu, S Ishimatsu, H Yamato, I Tanaka, | ||||||||
| Wistar male rats and ddY male mice were exposed to 500-10,000 ppm of methyl bromide gas up to 8 hours, and the survival time and weights of brain, lung, liver, kidneys, spleen and tests were measured. The survival time decreased with the gas concentration almost exponentially. In general, rats had a longer survival time than mice under the same exposure concentration. Difference of survival time between rats and mice was remarkable at low concentrations but small at high concentrations. Spleen weight decreased significantly and kidney weights tended to increase at 2000 ppm or greater exposure concentrations. Difference between wet and dry lung weight in the exposure group was significantly greater than that in the control group, especially for high concentrations, which suggested pulmonary edema or bronchopneumonia. | ||||||||
| 6938 | 3.23 | 18367873 | 2008.11.18 | + | + | Paclitaxel-loaded poly(D,L-lactide-co-glycolide) nanoparticles for radiotherapy in hypoxic human tumor cells in vitro. | Cancer Biol Ther | |
| C Jin, L Bai, H Wu, J Liu, G Guo, J Chen, | ||||||||
| Radioresistant hypoxic cells may contribute to the failure of radiation therapy in controlling certain tumors. Some studies have suggested the radiosensitizing effect of paclitaxel. The poly (D,L-lactide-co-glycolide)(PLGA) nanoparticles containing paclitaxel were prepared by o/w emulsification-solvent evaporation method. The physicochemical characteristics of the nanoparticles (i.e., encapsulation efficiency, particle size distribution, morphology, in vitro release) were studied. The morphology of the two human tumor cell lines: a carcinoma cervicis (HeLa) and a hepatoma (HepG(2)), treated with paclitaxel-loaded nanoparticles was photomicrographed. Flow cytometry was used to quantify the number of the tumor cells held in the G(2)/M phase of the cell cycle. The cellular uptake of nanoparticles was evaluated by transmission electronic microscopy. Cell viability was determined by the ability of single cell to form colonies in vitro. The prepared nanoparticles were spherical in shape with size between 200 nm and 800 nm. The encapsulation efficiency was 85.5%. The release behaviour of paclitaxel from the nanoparticles exhibited a biphasic pattern characterised by a fast initial release during the first 24 h, followed by a slower and continuous release. Co-culture of the two tumor cell lines with paclitaxel-loaded nanoparticles demonstrated that the cell morphology was changed and the released paclitaxel retained its bioactivity to block cells in the G(2)/M phase. The cellular uptake of nanoparticles was observed. The free paclitaxel and paclitaxel-loaded nanoparticles effectively sensitized hypoxic HeLa and HepG(2) cells to radiation. Under this experimental condition, the radiosensitization of paclitaxel-loaded nanoparticles was more significant than that of free paclitaxel. | ||||||||
| 6939 | 3.23 | 16039660 | 2006.11.24 | + | + | Preparation and characterization of aqueous colloids of Pt-Ru nanoparticles. | J Colloid Interface Sci | |
| Y Shimazaki, Y Kobayashi, S Yamada, T Miwa, M Konno, | ||||||||
| A synthetic method for platinum-ruthenium (PtRu) nanoparticles in aqueous media is proposed. This method employs citric acid as a capping agent and NaBH(4) as a reducing agent with the aid of pH control. The number-averaged size of the PtRu nanoparticles was ca. 2 nm. The crystal phase and chemical composition of the nanoparticles was investigated by X-ray diffraction measurement and scanning transmission electron microscopy coupled with energy-dispersive X-ray spectroscopy analysis, which indicated that the nanoparticles mainly consisted of an alloy of Pt and Ru. Electrochemical measurement showed that the PtRu nanoparticles had catalytic activity for methanol oxidation. | ||||||||
| 6940 | 3.23 | 17944550 | 2008.10.28 | + | + | Metals affect soil bacterial and fungal functional diversity differently. | Environ Toxicol Chem | |
| AM Stefanowicz, M Niklińska, R Laskowski, | ||||||||
| Heavy metals can cause a decrease in the taxonomic diversity of soil communities. Because of functional redundancy, it remains unclear to what extent different functions performed by the soil microbial communities may be affected by pollution. We studied the impact of metal contamination on soil bacterial and fungal functional diversity, active microbial biomass, and soil respiration rate. Soil samples were collected from 39 sites along three forest and five meadow pollution transects near an abandoned Pb/Zn smelter in Avonmouth (UK) and Ni smelter in Clydach (UK), in a Cu mining and smelting region near Glogów (Poland), and in a Zn/Pb mining and smelting region near Olkusz (Poland). Biolog GN2 and SFN2 plates were used to study the bacterial and fungal functional diversity, which subsequently was expressed as Shannon's diversity index (H'). The active microbial biomass was measured as substrate-induced respiration. We found that the bacterial functional diversity significantly decreased, whereas the fungal functional diversity slightly increased, with increasing metal concentration. We also observed a slight negative effect of metal pollution on the active microbial biomass. No relationship was found between metal contamination and total soil respiration rate. This suggests a higher sensitivity of bacterial functional diversity as an indicator for the effects of metal pollution compared with overall soil respiration. All microbial parameters were affected by nutrient concentrations and/or soil pH. | ||||||||
| 6941 | 3.23 | 15046782 | 2005.05.09 | + | + | Optimisation of the comet genotoxicity assay in freshly isolated murine hepatocytes: detection of strong in vitro DNA damaging properties for styrene. | Toxicol In Vitro | |
| FR Fontaine, YC DeGraaf, R Ghaoui, BC Sallustio, J Edwards, PC Burcham, | ||||||||
| While the comet assay is used to detect DNA damage in isolated cells following exposure to chemicals in vitro, few publications report the use of the procedure in liver cells isolated from mice. Our initial efforts to use the assay to assess DNA damage in mouse hepatocytes maintained on collagen-coated dishes were hampered by high levels of baseline damage in controls, which appeared to result from mechanical damage sustained during the dislodgement of adherent cells in the early stages of the assay protocol. Here we describe an efficient version of the comet assay in cultured mouse hepatocytes that involves careful recovery of cells using a "scraping" buffer supplemented with 10% high purity grade DMSO. Use of this buffer strongly diminished the frequency of false positives. Using the industrial reagent styrene as a positive control in the optimised procedure, non-cytotoxic concentrations of this substance (2.5-10 mM) significantly increased mean comet tail length, area, and moment. Co-incubation with the CYP inhibitor SKF-525A strongly attenuated these effects of styrene. Collectively, these findings confirm this method is highly suitable for the detection of DNA damage by bioactivation-dependent compounds in freshly isolated mouse hepatocytes. | ||||||||
| 6942 | 3.23 | 3351984 | 1988.05.04 | + | + | DNA strand breaks induced by hydrogen peroxide in isolated rat hepatocytes. | J Toxicol Environ Health | |
| MJ Olson, | ||||||||
| It has been proposed that increased rates of hepatic hydrogen peroxide (H2O2) production may initiate or promote the liver tumors that appear following chronic exposure of rodents to chemicals that cause peroxisome proliferation. However, the effect of H2O2 on the structural integrity of DNA in parenchymal hepatocytes, the target cells of peroxisome proliferator-induced carcinogenesis, is largely uncharacterized. Furthermore, oxidant-induced cellular damage has been invoked as causal of a number of hepatotoxic effects associated with exposure to chemicals other than peroxisome proliferators. For these reasons, alkaline elution analysis was used to study the action of H2O2, added exogenously, on DNA of intact, isolated rat hepatocytes. Addition of a bolus of H2O2 (0.01-1.0 mM) to monolayer cultures of hepatocytes caused concentration-dependent increases in single-strand DNA breaks (SSDB), which were maximal within 30 min of exposure. Cytotoxicity, as measured by lactate dehydrogenase (LDH) release, was minimal during a 1-h exposure to H2O2 concentrations less than 1 mM, but the efflux of oxidized glutathione was increased. Formation of SSDB was nearly linear with respect to H2O2 concentration in the range 0.1-1.0 mM. No double-strand DNA breaks or DNA-protein crosslinks were identified at H2O2 concentrations of 1 mM or less. Repair of SSDB in H2O2-free medium occurred in a rapid, linear manner only for the first 15 min, resulting in disappearance of 65% of the SSDB. A second, slower phase of SSDB rejoining occurred between 20 and 60 min of incubation in H2O2-free media; at 60 min rejoining was maximal (80% repair). These results define a specific type of DNA damage associated with H2O2 exposure of hepatocytes and suggest that primary cultures of rat hepatocytes are a suitable model for characterizing the potential genotoxic effects of oxidants, particularly excess H2O2 that may occur in the livers of animals exposed chronically to peroxisome proliferators. | ||||||||
| 6943 | 3.23 | 18477817 | 2008.06.27 | + | + | Efficient gene delivery using chitosan-polyethylenimine hybrid systems. | Biomed Mater | |
| HL Jiang, TH Kim, YK Kim, IY Park, MH Cho, CS Cho, | ||||||||
| Chitosan and chitosan derivatives have been investigated as non-viral vectors because they have several advantages, such as biocompatibility, biodegradability, low cytotoxicity and low immunogenicity. However, low transfection efficiency and low cell specificity must be solved for their use in clinical trials. In this paper, chitosan-polyethylenimine (PEI) hybrid systems such as chitosan/PEI blend and chitosan-graft-PEI are described for efficient gene delivery because the PEI has high transfection efficiency owing to a proton sponge effect and chitosan has biocompatibility. Also, hepatocyte specificity of the galactosylated chitosan is explained after combination with PEI. | ||||||||
| 6944 | 3.23 | 15745027 | 2006.01.06 | + | + | Preparation of PAMAM- and PPI-metal (silver, platinum, and palladium) nanocomposites and their catalytic activities for reduction of 4-nitrophenol. | Langmuir | |
| K Esumi, R Isono, T Yoshimura, | ||||||||
| Dendrimer-metal (silver, platinum, and palladium) nanocomposites are prepared in aqueous solutions containing poly(amidoamine) (PAMAM) dendrimers with surface amino groups (generations 3, 4, and 5) or poly(propyleneimine) (PPI) dendrimers with surface amino groups (generations 2, 3, and 4). The particle sizes of the metal nanoparticles obtained are almost independent of the generation as well as the concentration of the dendrimer for both the PAMAM and the PPI dendrimers; the average sizes of silver, platinum, and palladium nanoparticles are 5.6-7.5, 1.2-1.6, and 1.6-2.0 nm, respectively. It is suggested that the dendrimer-metal nanocomposites are formed by adsorbing the dendrimers on the metal nanoparticles. Studies of the reduction reaction of 4-nitrophenol by these nanocomposites show that the rate constants are very similar between PAMAM and PPI dendrimer-silver nanocomposites, whereas the rate constants for the PPI dendrimer-platinum and -palladium nanocomposites are greater than those for the corresponding PAMAM dendrimer nanocomposites. In addition, it is found that the rate constants for the reduction of 4-nitrophenol involving all the dendrimer-metal nanocomposites decrease with an increase in the dendrimer concentrations, and the catalytic activity of dendrimer-palladium nanocomposites is highest. | ||||||||
| 6945 | 3.22 | 17935941 | 2008.03.20 | + | + | Differential expression of genes associated with cell proliferation and apoptosis induced by okadaic acid during the transformation process of BALB/c 3T3 cells. | Toxicol In Vitro | |
| L Ao, JY Liu, LH Gao, SX Liu, MS Yang, MH Huang, J Cao, | ||||||||
| Okadaic acid (OA) is a tumor promoter in two-stage carcinogenesis experiments. Nevertheless, the effects of OA on cell transformation, cell proliferation and apoptosis vary widely, and the molecular events underlying these effects of OA are not well understood. In the present study, we examined the promoting activity and the associated effects on cell growth and apoptosis mediated by OA in BALB/c 3T3 cells, and evaluated alterations of gene transcriptional expression by microarray analysis. The promoting activity of OA was estimated by a two-stage transformation assay, in which cells were treated first with a low dose of the initiator N-methyl-N'-nitro-N-nitrosoguanidine (MNNG) and then with OA for 14 days. It showed that OA, at concentrations of 7.8-31.3 ng/ml, enhanced the transformation of MNNG-treated cells. In the promotion phase, cells exposed to OA (7.8 ng/ml) grew slowly for the first 2 days and subsequently died. As determined by Hoechst 33342 fluorescent dye and Annexin-V/PI dual-colored flow cytometry, OA induced morphologically apoptotic cells and increased the percentage of early apoptotic cells. The gene expression profile induced by OA at five time points in the promotion phase was determined by use of a specific mouse toxicological microarray containing 1796 clones, and a total of 177 differentially expressed genes were identified. By gene ontology analysis, 31 of these were determined to be functionally involved with cell growth and/or maintenance. In this group, numerous genes associated with the cell proliferation and cell cycle progression were down-regulated at early and/or middle time points. Among these was a subset of genes associated with apoptosis, in which Bnip3, Cycs, Casp3 and Bag1 genes are involved in the mitochondrial pathway of apoptosis. Ier3, Mdm2 and Bnip3 genes may be p53 targets. Furthermore, real-time PCR confirmed the expression changes of five genes selected at random from the differentially expressed genes. We conclude that OA induces cell growth inhibition and apoptosis in the two-stage, MNNG-initiated transformation of BALB/c 3T3 cells. The results of gene expression profile analysis imply that multiple molecular pathways are involved in OA-induced proliferation inhibition and apoptosis. Mitochondrial and p53-associated apoptotic pathways also may contribute to OA-induced apoptosis. | ||||||||
| 6946 | 3.22 | 15884368 | 2005.08.24 | + | + | Five-stage environmental exposure assessment strategy for mixtures: gasoline as a case study. | Environ Sci Technol | |
| KL Foster, D Mackay, TF Parkerton, E Webster, L Milford, | ||||||||
| A five-stage strategy is suggested for conducting an exposure assessment of mixtures that may contain numerous chemical components. The stages are: (1) determination of mixture composition and variability, (2) selection of component groups within the mixture and documentation of criteria used for this selection, (3) compilation of relevant property data for each group, (4) assessment of environmental fate of each group, and (5) assessment of environmental and human exposure to each group and to the mixture as a whole. A subsequent step is the assessment of environmental and/or human risk associated with the individual and aggregate exposure to each group. The approach is illustrated by application to gasoline, which is treated as 24 component groups or hydrocarbon blocks. Focusing on stages 2-4, the illustration shows that the groups display widely different environmental fates as a result of their different physicochemical properties, degradation half-lives, and mode-of-entry into the environment. As a result, the relative proportions of groups in each environmental medium (such as air and water) differ greatly from that of the original mixture. It is thus important to treat gasoline and similar mixtures as a number of component groups instead of as a single substance. A generic procedure is suggested in which the model is run for unit emissions of each component group to air, water, and soil. These results are compiled into matrices that can then be conveniently scaled to actual emission rates without rerunning the model. Methods for determining subsequent exposure and risk are also briefly outlined. | ||||||||
| 6947 | 3.22 | 17851620 | 2007.10.23 | + | + | Multifunctionalised cationic fullerene adducts for gene transfer: design, synthesis and DNA complexation. | Chem Commun (Camb) | |
| C Klumpp, L Lacerda, O Chaloin, T Da Ros, K Kostarelos, M Prato, A Bianco, | ||||||||
| Cationic poly-N,N-dimethylfulleropyrrolidinium derivatives have been designed and synthesised to complex plasmid DNA for gene delivery. | ||||||||
| 6948 | 3.22 | 18242900 | 2008.09.03 | + | + | Amphotericin B-incorporated polymeric micelles composed of poly(d,l-lactide-co-glycolide)/dextran graft copolymer. | Int J Pharm | |
| KC Choi, JY Bang, PI Kim, C Kim, CE Song, | ||||||||
| In this study, we prepared amphotericin B (AmpB)-encapsulated polymeric micelle of poly(d,l-lactide-co-glycolide) (PLGA) grafted-dextran (DexLG) copolymer and characterized its physicochemical properties in vitro. The average particle size of AmpB-encpasulated DexLG polymeric micelles was around 30-150nm while particle size of empty polymeric micelles was below 100nm according to the copolymer composition. The morphology of AmpB-encapsulated polymeric micelle of DexLG copolymer was spherical shapes at transmission electron microscopy (TEM) observation. At 1H NMR study, specific peaks of AmpB and DexLG copolymer was obtained at DMSO but specific peaks characterized to AmpB and PLGA was disappeared at D2O environment. These results indicated that AmpB was encapsulated into the micellar core of polymeric micelle. XRD results also support these results, indicating that specific crystal peaks of AmpB and broad peaks of DexLG copolymer were obtained but specific peaks of AmpB was disappeared at polymeric micelles while physical mixture of AmpB/empty polymeric micelles showed both specific peaks. Drug release rate was decreased according to the increase of drug contents and increase of PLGA component of DexLG copolymer. At the minimal inhibition concentration (MIC) study using Candida albicans, AmpB-encapsulated polymeric micelle showed almost similar effectives on the growth inhibition of microorganisms. These showed that AmpB-encapsulated polymeric micelle of DexLG copolymer can be considered to potential antifungal agent carriers. | ||||||||
| 6949 | 3.22 | 6186484 | 1983.04.21 | + | + | Sampling of vehicle emissions for chemical analysis and biological testing. | Environ Health Perspect | |
| D Schuetzle, | ||||||||
| Representative dilution tube sampling techniques for particulate and gas phase vehicle emissions are described using Teflon filter media and XAD-2 resin. More than 90% of the total gas (C8-C18) and particulate direct acting Ames assay mutagenicity (TA 98) was found in the particulate phase. The gas and particulate phase material was fractionated by HPLC into nonpolar, moderately polar and highly polar chemical fractions. The moderately polar chemical fraction of the particulates contained more than 50% of the direct acting Ames assay mutagenicity for the total extract. The concentration of oxygenated polynuclear aromatic hydrocarbons (oxy-PAH) and nitrated PAH (nitro-PAH) identified in the moderately polar particulate fractions are given. Nitro-PAH account for most of the direct-acting (TA 98) Ames assay mutagenicity in these moderately polar fractions. Reactions and kinetic expressions for chemical conversion of PAH are presented. Chemical conversion of PAH to nitro-PAH during dilution tube sampling of particulates on Teflon filters and gases on XAD-2 resin is a minor problem (representing 10-20%, on the average, of the 1-nitropyrene found in extracts) at short (46 min) sampling times, at low sampling temperatures (42 degrees C), and in diluted exhaust containing 3 ppm NO2. Particulate emissions collected from dilution tubes on filter media appear to be representative of what is emitted in the environment as based upon a comparison of highway and laboratory studies. | ||||||||
| 6950 | 3.22 | 14979548 | 2004.05.19 | + | + | Using bioluminescent biosensors for hazard analysis and critical control point (HACCP) in wastewater control. | Water Sci Technol | |
| C Valat, D Champiat, JR Degorce-Dumas, O Thomas, | ||||||||
| Starting from a new approach for water pollution control and wastewater treatment plant management, the hazard analysis and critical control point (HACCP) quality concept, the interest for the development of new rapid and sensitive methods such as bioluminescence-based methods is evident. After an introduction of the HACCP procedure, a bibliographic study of the bioluminescence potentiality is presented and discussed. | ||||||||
| 6951 | 3.22 | 18441823 | 2008.07.31 | + | + | Bactericidal activity of a Ce-promoted Ag/AlPO4 catalyst using molecular oxygen in water. | Environ Sci Technol | |
| Q Chang, H He, J Zhao, M Yang, J Qut, | ||||||||
| The catalytic inactivation of Escherichia coli in water by a cerium (Ce)-promoted silver-loaded aluminum phosphate (Ag/ AlPO4) catalyst using molecular oxygen was investigated. With optimum Ce content, the Ag(Ce)/AlPO4 catalyst exhibited strong bactericidal activity. The process of decomposition of the cell wall and cell membrane was directly observed by TEM. The different morphological changes of E. coli cells treated with the Ag(Ce)/AlPO4 catalyst and those treated with Ag+ suggested that the Ag+ eluted from the catalyst surface did not play an important role during the bactericidal process. Results of DMPO spin-trapping measurements by electron spin resonance (ESR) indicated the formation of the reactive oxygen species (ROS) *OH and *O2-, which caused the considerable bactericidal activity. The formation of H2O2 acted as an important intermediate; this was confirmed by addition of catalase as the scavenger. A possible catalytic oxidation bactericidal mechanism using molecular oxygen was proposed for the Ag(Ce)/AlPO4 catalyst. | ||||||||
| 6952 | 3.21 | 17989807 | 2008.01.24 | + | + | Characterization of surface water on Au core Pt-group metal shell nanoparticles coated electrodes by surface-enhanced Raman spectroscopy. | Chem Commun (Camb) | |
| YX Jiang, JF Li, DY Wu, ZL Yang, B Ren, JW Hu, YL Chow, ZQ Tian, | ||||||||
| We utilized the strategy of 'borrowing SERS activity', by chemically coating several atomic layers of a Pt-group metal on highly SERS-active Au nanoparticles, to obtain the first SERS (also Raman) spectra of surface water on Pt and Pd metals, and propose conceptual models for water adsorbed on Pt and Pd metal surfaces. | ||||||||
| 6953 | 3.21 | 18049763 | 2008.02.05 | + | + | Removal of amorphous carbon for the efficient sidewall functionalisation of single-walled carbon nanotubes. | Chem Commun (Camb) | |
| L Shao, G Tobias, CG Salzmann, B Ballesteros, SY Hong, A Crossley, BG Davis, ML Green, | ||||||||
| The sidewall functionalisation of carbon nanotubes using the standard nitric acid treatment can be greatly enhanced by first removing the amorphous carbon present in the sample. | ||||||||
| 6954 | 3.21 | 12859150 | 2003.10.09 | + | + | Zinc octa-n-alkyl phthalocyanines in photodynamic therapy: photophysical properties, accumulation and apoptosis in cell cultures, studies in erythrocytes and topical application to Balb/c mice skin. | Photochem Photobiol Sci | |
| L Kaestner, M Cesson, K Kassab, T Christensen, PD Edminson, MJ Cook, I Chambrier, G Jori, | ||||||||
| Two octa-substituted phthalocyanines, namely 1,4,8,11,15,18,22,25-octakis(decyl)phthalocyaninato zinc(II) (ZnODPc) and 1,4,8,11,15,18,22,25-octakis(pentyl)phthalocyaninato zinc(II) (ZnOPPc), were investigated for their use in photodynamic therapy (PDT) after topical application. Both substances exhibited favourable properties as photosensitisers in vitro: absorption maxima around 700 nm with absorption coefficients of about 190000 (M(-1) cm(-1)), a singlet oxygen quantum yield of 0.47 +/- 0.02 (ZnODPc), and good accumulation in keratinocytes and fibroblasts. Cell death after phthalocyanine-photosensitisation appeared to occur mainly via apoptosis. The in vivo experiments demonstrated a good accumulation of the phthalocyanines after topical application in a tetrahydrofuran-azone formulation onto the dorsal skin of Balb/c mice: [(4.6-4.7) +/- 1.0]% of deposited dye could be recovered after 3 h from deposition. ZnODPc showed significantly better skin-photosensitising properties than ZnOPPc and is therefore a potential candidate for the treatment of psoriasis. | ||||||||
| 6955 | 3.21 | 18654209 | 2008.09.10 | + | + | Effect of supramolecular structure on polymer nanofibre elasticity. | Nat Nanotechnol | |
| A Arinstein, M Burman, O Gendelman, E Zussman, | ||||||||
| Polymer materials of reduced size and dimensionality, such as thin films, polymer nanofibres and nanotubes, exhibit exceptional mechanical properties compared with those of their macroscopic counterparts. We discuss here the abrupt increase in Young's modulus in polymer nanofibres. Using scaling estimation we show that this effect occurs when, in the amorphous (non-crystalline) part of the nanofibres, the transversal size of regions consisting of orientation-correlated macromolecules is comparable to the nanofibre diameter, thereby resulting in confinement of the supramolecular structure. We suggest that in polymer nanofibres the resulting supramolecular microstructure plays a more dominant role in the deformation process than previously thought, challenging the commonly held view that surface effects are most significant. The concept we develop also provides a way to interpret the observed--but not yet understood--temperature dependence of Young's modulus in nanofibres of different diameters. | ||||||||
| 6956 | 3.21 | 10218668 | 1999.06.10 | + | The relative importance of HO* and ONOO- in mediating the toxicity of O*-. | Free Radic Biol Med | ||
| SI Liochev, I Fridovich, | ||||||||
| 6957 | 3.21 | 2283261 | 1991.03.20 | + | Superparamagnetic contrast agents for magnetic resonance imaging. | Invest Radiol | ||
| HG Gundersen, T Bach-Gansmo, E Holtz, AK Fahlvik, A Berg, | ||||||||
| 6958 | 3.21 | 16913132 | 2007.03.16 | + | + | Evaluation of the Dekati mass monitor for the measurement of exhaust particle mass emissions. | Environ Sci Technol | |
| A Mamakos, L Ntziachristos, Z Samaras, | ||||||||
| The Dekati mass monitor (OMM) is an instrument which measures the mass concentration of airborne particles in real time by combining aerodynamic and mobility size particle classification. In this study, we evaluate the performance of the DMM by sampling exhaust from five engines and vehicles of different technologies in both steady-state and transient tests. DMM results are found higher than the filter-based particulate matter (PM) by 39 +/- 24% (range stands for +/- one standard deviation) for 62 diesel tests conducted in total and 3% and 14% higher, respectively, in two gasoline tests. To explore whether the difference occurs because of the different measurement principles of DMM and filter-based PM, the DMM operation is replicated over steady-state tests by combining an electrical low-pressure impactor (ELPI) and a scanning mobility particle sizer (SMPS). The correlation of ELPI and SMPS derived mass and filter-based PM is satisfactory (R2 = 0.95) with a mean deviation of 5 +/- 15%. For the same tests, the correlation of DMM with PM was also high (R2 = 0.95), but DMM exceeded PM by 44 +/- 23% on average. The comparison of ELPI and SMPS and DMM results reveals that the latter overestimates both the geometric mean diameter and especially the width of the particle mass-weighted size distribution. These findings demonstrate thatthe statistically significant difference between the DMM and the filter-based PM cannot just originate from the different measurement principles but also from the actual implementation of the combined aerodynamic-mobility measurement in the DMM. Optimizing the DMM will require changes in its design and/or the calculation algorithm to improve the resolution and width of the aerodynamic size distribution recorded. | ||||||||
| 6959 | 3.21 | 15491643 | 2005.02.22 | + | + | MNNG-induced mutations in the adult gill and hepatopancreas and in embryos of rpsL transgenic zebrafish. | Mutat Res | |
| K Amanuma, T Nakamura, Y Aoki, | ||||||||
| To evaluate the feasibility of a mutagenicity assay using adult rpsL transgenic zebrafish, 4- to 8-month-old females were exposed to N-methyl-N'-nitro-N-nitrosoguanidine (MNNG) (0, 15 or 30 mg/L in a water bath for 2 h). At 2 weeks after exposure, MNNG showed a concentration-dependent significant increase in mutant frequency (MF) of 8 x 10(-5), 18 x 10(-5), and 51 x 10(-5), respectively, in the gill. DNA sequencing revealed that 60-74% of the induced mutations were G:C to A:T transitions, consistent with the known mutagenic effects of MNNG. A marginal but significant increase in MF was observed in the hepatopancreas only in the group exposed to 30 mg/L, with the induction of some G:C to A:T transitions. A time-course of the appearance of mutations was determined in fish treated with 15 mg/L MNNG. In both, the gill and hepatopancreas, a higher MF was observed at 3 weeks than at 2 weeks, suggesting that an expression time of at least 3 weeks is preferable for the assay. When embryos (29 h post-fertilization) were exposed to MNNG (0, 50, and 150 mg/L) for 1 h, MFs increased significantly with an increase in the concentration of MNNG (5 x 10(-5), 40 x 10(-5), and 144 x 10(-5), respectively) at 3 days after exposure. G:C to A:T transitions were the predominant mutations, and these occurred at the same sites in the rpsL gene as in adult tissues. Thus, MNNG induces typical mutations in the gill and hepatopancreas of adult fish, and in embryos, suggesting that the rpsL zebrafish is a useful tool for monitoring genotoxicity caused by water-borne mutagens. | ||||||||
| 6960 | 3.21 | 17611055 | 2008.01.16 | + | + | Potentialities of silica/alginate nanoparticles as hybrid magnetic carriers. | Int J Pharm | |
| M Boissière, J Allouche, C Chanéac, R Brayner, JM Devoisselle, J Livage, T Coradin, | ||||||||
| The possibility to associate traditional bio-organic capsules, such as polymer nanoparticles or liposomes, with silica has been recently demonstrated, opening the route to the design of novel nanocomposites that exhibit promising properties as drug carriers. In this context, we describe here the elaboration of silica/alginate nanoparticles incorporating magnetic iron oxide colloids and fluorescent carboxy-fluoroscein. These nanocomposites were characterized by electron microscopy, X-ray diffraction and magnetic measurements. The release of the fluorophore was investigated in vitro and was demonstrated to occur in 3T3 fibroblast cells. Further grafting of organic moieties on particle surface is also described. These data suggest that hybrid nanoparticles are flexible platforms for the developments of multi-functional bio-capsules. | ||||||||
| 6961 | 3.21 | 15849717 | 2005.08.12 | + | + | Response of the antioxidant defense system to tert-butyl hydroperoxide and hydrogen peroxide in a human hepatoma cell line (HepG2). | J Biochem Mol Toxicol | |
| M Alía, S Ramos, R Mateos, L Bravo, L Goya, | ||||||||
| The aim of this work was to investigate the response of the antioxidant defense system to two oxidative stressors, hydrogen peroxide and tert-butyl hydroperoxide, in HepG2 cells in culture. The parameters evaluated included enzyme activity and gene expression of superoxide dismutase, catalase, glutathione peroxidase, and activity of glutathione reductase. Besides, markers of the cell damage and oxidative stress evoked by the stressors such as cell viability, intracellular reactive oxygen species generation, malondialdehyde levels, and reduced glutathione concentration were evaluated. Both stressors, hydrogen peroxide and tert-butyl hydroperoxide, enhanced cell damage and reactive oxygen species generation at doses above 50 microM. The concentration of reduced glutathione decreased, and levels of malondialdehyde and activity of the antioxidant enzymes consistently increased only when HepG2 cells were treated with tert-butyl hydroperoxide but not when hydrogen peroxide was used. A slight increase in the gene expression of Cu/Zn superoxide dismutase and catalase with 500 microM tert-butyl hydroperoxide and of catalase with 200 microM hydrogen peroxide was observed. The response of the components of the antioxidant defense system evaluated in this study indicates that tert-butyl hydroperoxide evokes a consistent cellular stress in HepG2. | ||||||||
| 6962 | 3.21 | 17141308 | 2007.03.07 | + | + | Bio-functional micelles self-assembled from a folate-conjugated block copolymer for targeted intracellular delivery of anticancer drugs. | Biomaterials | |
| SQ Liu, N Wiradharma, SJ Gao, YW Tong, YY Yang, | ||||||||
| In this study, a block copolymer, poly(N-isopropylacrylamide-co-N,N-dimethylacrylamide-co-2-aminoethyl methacrylate)-b-poly(10-undecenoic acid) (P(NIPAAm-co-DMAAm-co-AMA)-b-PUA) was synthesized, and folic acid was conjugated to the hydrophilic block through the amine group in AMA. This polymer was self-assembled into micelles, which exhibited pH-induced temperature sensitivity. They were smaller in size, and possessed a better-defined core-shell structure as well as more stable hydrophobic core than the random copolymer P(NIPAAm-co-DMAAm-co-UA), and provided a shell with folate molecules. An anti-cancer drug, doxorubicin (DOX) was encapsulated into the micelles. The mean diameter of the blank and DOX-loaded micelles was less than 100 nm. DOX release was pH-dependent, being faster at low pH (endosomes/lysosomes). Therefore, DOX was readily released from the micelles into the nucleus after being taken up. More importantly, IC50 of DOX-loaded micelles with folate against folate receptor-expressing 4T1 and KB cells was much lower than that of the DOX-loaded micelles without folate (3.8 vs. 7.6 mg/L for 4T1 cells and 1.2 vs. 3.0mg/L for KB cells). In vivo experiments conducted in a 4T1 mouse breast cancer model demonstrated that DOX-loaded micelles had a longer blood circulation time than free DOX (t(1/2): 30 min and 140 min, respectively). In addition, the micelles delivered an increased amount of DOX to the tumor when compared to free DOX. These bio-functional micelles may make a promising carrier to transport anticancer drugs specifically to tumor cells and release the drug molecules inside the cells to the cytosols for improved chemotherapy. | ||||||||
| 6963 | 3.21 | 17292150 | 2007.05.11 | + | + | Biocompatible nanofiber scaffolds on metal for controlled release and cell colonization. | Nanomedicine | |
| W Dong, T Zhang, M McDonald, C Padilla, J Epstein, ZR Tian, | ||||||||
| This paper reports for the first time a preparation of biocompatible titanate nanofiber scaffolds on the surface of titanium foil/mesh via a one-step hydrothermal reaction. The length and diameter of the nanofibers can be controlled by varying the fabrication parameters, such as reaction temperature, precursor concentration, and reaction time. The nanofibers can self-organize into macroporous (mostly 0.5-10 microm in diameter) scaffolds potentially useful for developing new bioscaffolds, photocatalysts, sensors, and drug delivery vehicles. | ||||||||
| 6964 | 3.21 | 16403551 | 2006.10.24 | + | + | An exposure assessment for selected pharmaceuticals within a watershed in Southern Ontario. | Chemosphere | |
| L Lissemore, C Hao, P Yang, PK Sibley, S Mabury, KR Solomon, | ||||||||
| Recent studies from a number of countries have shown that measurable concentrations of both human and veterinary pharmaceuticals can be found in a variety of environmental matrices such as surface and ground water, soils, and sediments. Few data are available that characterize the sources, exposure and effects of pharmaceuticals in the environment and there is clearly a need to define these parameters within a Canadian context. We present in this paper the first report in southern Ontario, Canada on the geographic and temporal distribution of pharmaceuticals detected within seven tributaries receiving primarily agricultural inputs in a typical watershed. Of the 28 pharmaceuticals surveyed, 14 were detected in the streams sampled (n=125). Temporal trends in concentration for five frequently detected pharmaceuticals show pulses occurring between May and November of 2003 at similar but varying times over the seasons, depending on the pharmaceuticals, flow rate, and precipitation. Fluctuations in concentration of ions indicative of agricultural run off, such as nitrate and phosphate, were not found to be useful predictors of changes in pharmaceutical concentration (P>0.4), however a significant correlation between dissolved organic carbon and monensin and carbamazepine concentrations were observed (P<0.013). Exposure profiles illustrating concentration distributions for three of the more prevalent pharmaceuticals detected, including lincomycin, monensin and carbamazepine, showed a log normal distribution, useful for calculating centiles of environmental concentrations. While distributions of estimated total potency of pharmaceuticals detected in the surface waters suggested small risks of environmental effects of mixtures to daphnia, green algae, Lemna gibba, and fish, the significance of non-target effects and impacts due to chronic low level exposures to chemical mixtures remains unclear. | ||||||||
| 6965 | 3.21 | 16697459 | 2008.02.21 | + | + | Effects of algal extracts (Polysiphonia fucoides) on rainbow trout (Oncorhynchus mykiss): a biomarker approach. | Mar Environ Res | |
| I Del Barga, G Frenzilli, V Scarcelli, M Nigro, A Malmvärn, L Asplund, L Förlin, J Sturve, | ||||||||
| The genotoxicity of algal extracts (Polysiphonia fucoides) was investigated in erythrocytes of rainbow trout (Oncorhynchus mykiss). Trout were exposed to 0.5% of the algal extract for 7 days. Comet assay (alkaline and neutral versions) and Micronucleus test were used to assess DNA damage, and Diffusion Assay to detect apoptotic cells. EROD activities and oxidative stress parameters in rainbow trout liver were also measured. A significant induction of DNA single strand breaks comparable to the ones induced by the in vivo exposure to 20 mg/kg B[a]P was observed at the end of the treatment, while increases of double strand breaks and apoptotic cells were not observed. The absence of activation of antioxidant responses seems to underline a mechanism of action of the genotoxic algal extract which does not involve oxidative stress. | ||||||||
| 6966 | 3.21 | 15625776 | 2005.04.08 | + | + | Evaluating the cytotoxicity of ionic liquids using human cell line HeLa. | Hum Exp Toxicol | |
| P Stepnowski, AC Składanowski, A Ludwiczak, E Laczyńska, | ||||||||
| This paper presents cytotoxicity data of selected imidazolium ionic liquids evaluated in vitro on the human tumor cell line HeLa. It was found that for 1-n-butyl-3-methylimidazolium entities the toxicity depends strongly on the associated anion; EC50 values are lowest for tetrafluoroborate. No direct dependence of the reduced effect concentration was found on elongating the short, methyl chain to ethyl or n-hexyl. Only for the ionic liquid with an n-decyl chain, the longest one studied, did higher hydrophobicity result in a EC50 one order of magnitude lower than that obtained with the n-butyl entity. The effect concentrations of imidazolium ionic liquids in the HeLa system used are lower than the values obtained for conventional organic solvents such as dichloromethane, toluene or xylene. | ||||||||
| 6967 | 3.21 | 14643333 | 2004.08.06 | + | + | Antibacterial and antiproliferative activity of cationic fullerene derivatives. | Bioorg Med Chem Lett | |
| T Mashino, D Nishikawa, K Takahashi, N Usui, T Yamori, M Seki, T Endo, M Mochizuki, | ||||||||
| We examined the antibacterial and antiproliferative activities of alkylated C(60)-bis(N,N-dimethylpyrrolidinium iodide) derivatives. The fullerene derivatives inhibited bacteria and cancer cell growth effectively. However, the fullerene derivatives with a long alkyl chain did not show antibacterial activity. | ||||||||
| 6968 | 3.20 | 16032835 | 2006.06.23 | + | + | Stöber synthesis of monodispersed luminescent silica nanoparticles for bioanalytical assays. | Langmuir | |
| LM Rossi, L Shi, FH Quina, Z Rosenzweig, | ||||||||
| We have developed a simple method to prepare bright and photostable luminescent silica nanoparticles of different sizes and narrow size distribution in high yield. The method is based on the use of Stöber synthesis in the presence of a fluorophore to form bright silica nanoparticles. Unlike micro-emulsion-based methods often used to prepare luminescent silica particles, the Stöber method is a one-pot synthesis that is carried out at room temperature under alkaline conditions in ethanol:water mixtures and avoids the use of potentially toxic organic solvents and surfactants. Our luminescent particles contained the transition metal complex tris(1,10-phenanthroline) ruthenium(II) chloride, [Ru(phen)3]Cl2. They showed higher photostability and a longer fluorescence lifetime compared to free Ru(phen)3 solutions. Leakage of dye molecules from the silica particles was negligible, which was attributed to strong electrostatic attractions between the positively charged ruthenium complex and the negatively charged silica. To demonstrate the utility of the highly luminescent silica nanoparticles in bioassays, we further modified their surface with streptavidin and demonstrated their binding to biotinylated glass slides. The study showed that digital counting of the luminescent nanoparticles could be used as an attractive alternative to detection techniques involving analogue luminescence detection in bioanalytical assays. | ||||||||
| 6969 | 3.20 | 1322572 | 1992.08.28 | + | + | Assessment of toxicologic interactions resulting from acute inhalation exposure to sulfuric acid and ozone mixtures. | Toxicol Appl Pharmacol | |
| RB Schlesinger, JT Zelikoff, LC Chen, PL Kinney, | ||||||||
| Studies examining effects of air pollutants often use single compounds, while "real world" exposures are to more than one chemical. Thus, it is necessary to assess responses following inhalation of chemical mixtures. Rabbits were exposed for 3 hr to sulfuric acid aerosol at 0, 50, 75, or 125 micrograms/m3 in conjunction with ozone at 0, 0.1, 0.3, or 0.6 ppm, following which broncho-pulmonary lavage was performed. Various pulmonary response endpoints related to general cytotoxicity and macrophage function were examined. In addition, a goal of the study was to define an improved approach to the analysis of data sets involving binary pollutant mixtures. Results were evaluated using analysis of variance with multiple linear contrasts to determine the significance of any effect in the pollutant-exposed groups compared to sham control animals and to assess the type, and extent, of any toxicological interaction between acid and ozone. Interaction was considered to occur when the effects of combined exposure were either significantly greater or less than additive. Pollutant exposures had no effect on lavage fluid levels of lactate dehydrogenase, prostaglandins E2 and F2 alpha, nor on the numbers, viability, or types of immune cells recovered by lavage. Phagocytic activity of macrophages was depressed at the two highest acid levels and at all levels of ozone. Exposure to all mixtures showed significant antagonism. Superoxide production by stimulated macrophages was depressed by acid exposure at the two highest concentrations, while ozone alone had no effect. Significant antagonistic interaction was observed following exposure to mixtures of 75 or 125 micrograms/m3 acid with 0.1 or 0.3 ppm ozone. The activity of tumor necrosis factor elicited from stimulated macrophages was depressed by acid at 75 and 125 micrograms/m3 while ozone had no effect. Exposure to mixtures of 125 micrograms/m3 acid with 0.3 or 0.6 ppm ozone resulted in synergistic interaction. This study provided additional evidence for antagonism between two common air pollutants and demonstrated that the type of interaction between sulfuric acid and ozone depended upon the endpoint but that the magnitude of any interaction was not always related to the exposure concentrations of the constituent pollutants. | ||||||||
| 6970 | 3.20 | 8678799 | 1996.08.12 | + | + | Cytotoxic impact of DNA single vs double strand breaks in oxidatively injured cells. | Arch Toxicol Suppl | |
| O Cantoni, P Sestili, A Guidarelli, L Palomba, L Brambilla, F Cattabeni, | ||||||||
| Hydrogen peroxide is a potent inducer of DNA single strand breaks (SSBs) in cultured mammalian cells. These lesions, however, are efficiently repaired and do not appear to mediate the cytotoxic response. This inference is based on the observations that a) inhibiting the rate of SSB-removal does not result in an increased cytotoxicity; b) using different experimental conditions it is possible to dissociate the formation of DNA SSBs from the cytotoxic response; c) the induction/loss of the oxidant-resistant phenotype in cell variants characterized by different levels of resistance to the lethal effect of the oxidant does not correlate with resistance to DNA SSB-induction; d) a much larger accumulation of DNA SSBs can be observed following treatment with H2O2 at 4 degrees C, as compared to 37 degrees C, although the opposite is true in terms of cytotoxicity. In the presence of micromolar levels of L-Histidine, H2O2 also induces DNA double strand breaks (DSBs), a type of lesion which we suggest may mediate the lethal event. This conclusion finds experimental support in the following observations: a) DNA DSBs are generated at survival-range concentrations, and a linear correlation exists between the level of this lesion and cytotoxicity; b) this correlation curve overlaps with the curves generated under similar experimental conditions using different cell lines with different sensitivity to the oxidant alone, or different clones derived from the same cell line, some of which showed a high degree of resistance to H2O2. Finally, the formation of DNA DSBs appears to enhance both apoptotic and necrotic cell death. | ||||||||
| 6971 | 3.20 | 15461522 | 2006.04.25 | + | + | Formation of dispersed nanostructures from poly(ferrocenyldimethylsilane-b-dimethylsiloxane) nanotubes upon exposure to supercritical carbon dioxide. | Langmuir | |
| DJ Frankowski, J Raez, I Manners, MA Winnik, SA Khan, RJ Spontak, | ||||||||
| While incompatible block copolymers commonly assemble into several established classical or complex morphologies, highly asymmetric poly(ferrocenyldimethylsilane-b-dimethylsiloxane) (PFS-b-PDMS) diblock copolymers can also self-organize into high-aspect-ratio nanotubes with PDMS corona in the presence of PDMS-selective organic solvents. Exposure of these nanotubes on a carbon substrate to supercritical carbon dioxide (scCO2), also a PDMS-selective solvent, appears to promote partial dissolution of the copolymer molecules. At sufficiently high copolymer concentrations, the dissolved molecules subsequently re-organize within the scCO2 environment to form new copolymer nanostructures that redeposit on the substrate upon scCO2 depressurization. Transmission electron microscopy reveals that micelles form under all the conditions examined here, whereas nanotubes coalesce and vesicles develop only at relatively high temperatures. The extent to which the copolymer nanotubes dissolve and the size distribution of the replacement micelles are sensitive to exposure conditions. These results suggest that the phase behavior of PFS-b-PDMS diblock copolymers in scCO2 may be remarkably rich and easily tunable. | ||||||||
| 6972 | 3.20 | 8886758 | 1997.01.30 | + | + | Eosinophilic lung inflammation in particulate-induced lung injury: technical consideration in isolating RNA for gene expression studies. | Exp Lung Res | |
| UP Kodavanti, RH Jaskot, J Bonner, A Badgett, KL Dreher, | ||||||||
| Particulate and other pollutant exposures are associated with lung injury and inflammation. The purpose of this study was to develop an approach by which intact RNA could be obtained from inflamed lung tissue from particulate-exposed animals in order to correlate injury with specific gene expression. Male Sprague Dawley (SD) and Fischer-344 (F-344) rats were intratracheally instilled with saline or residual oil fly ash (ROFA) particles, 8.3 mg/kg body weight in saline. At various time points following ROFA instillation, lungs were either lavaged or used for RNA isolation. ROFA exposure produced an increase in bronchoalveolar lavage fluid (BALF) neutrophils in both SD and F-344 rats. A time-dependent increase in eosinophils occurred only in SD rats but not in F-344 rats. Extraction of inflamed pulmonary tissue having a high influx of eosinophils for RNA using the conventional acid guanidinium thiocyanate phenol-chloroform (AGPC) procedure failed to provide undegraded RNA suitable for RT-PCR and Northern blot analysis of beta-actin mRNA expression. Mixing intact total RNA from saline control rat lungs with degraded RNA samples from inflamed lung yielded a gel profile of degraded RNA, indicating the presence of ribonuclease-like activity in the RNA extracted from lung tissues having eosinophil influx. Evidently, the conventional AGPC procedure failed to completely remove ribonuclease activity associated with ROFA-induced pulmonary eosinophil influx. This study reports a single-step modification to the AGPC extraction method that does not require additional reagents or additional precipitation steps for extracting undegraded RNA from nuclease-rich inflamed lung tissue. The aqueous layer resulting from mixing homogenate and chloroform is extracted a second time using an equal volume of AGPC buffer followed by addition of chloroform and centrifugation. The second aqueous phase is then treated as described in the conventional RNA extraction protocol. This simple and convenient modification does not require multiple precipitations of RNA and yields undegraded RNA from inflamed lung tissue with a slightly higher A260/A280 ratio without affecting overall RNA recovery. The results indicate that undegraded RNA could not be isolated using the routine AGPC-based isolation technique from lung tissue containing eosinophils following ROFA exposure. The degraded RNA preparations were unsuitable for gene expression studies. However, undegraded RNA can be isolated from these tissues by modifying the original AGPC RNA extraction procedure, which is suitable for gene expression analysis using northern blot and RT-PCR techniques. | ||||||||
| 6973 | 3.20 | 11804737 | 2003.04.21 | + | + | Substratum nanotopography and the adhesion of biological cells. Are symmetry or regularity of nanotopography important? | Biophys Chem | |
| AS Curtis, B Casey, JO Gallagher, D Pasqui, MA Wood, CD Wilkinson, | ||||||||
| Animal cells live in environments where many of the features that surround them are on the nanoscale, for example detail on collagen molecules. Do cells react to objects of this size and if so, what features of the molecules are they responding to? Here we show, by fabricating nanometric features in silica and by casting reverse features in polycaprolactone and culturing vertebrate cells in culture upon them, that cells react in their adhesion to the features. With cliffs, adhesion is enhanced at the cliff edge, while pits or pillars in ordered arrays diminish adhesion. The results implicate ordered topography and possibly symmetry effects in the adhesion of cells. Parallel results were obtained in the adhesion of carboxylate-surfaced 2-microm-diameter particles to these surfaces. These results are in agreement with recent predictions from non-biological nanometric systems. | ||||||||
| 6974 | 3.20 | 15858857 | 2005.08.25 | + | + | Low molecular weight dextrans stabilize nonviral vectors during lyophilization at low osmolalities: concentrating suspensions by rehydration to reduced volumes. | J Pharm Sci | |
| TJ Anchordoquy, TK Armstrong, MC Molina, | ||||||||
| Stabilization of nonviral vectors during freezing and drying requires formulation with protective excipients such that transfection rates and physical characteristics are maintained upon reconstitution. While many studies have demonstrated the ability of disaccharides (e.g., sucrose) to effectively protect nonviral vectors during lyophilization, the sucrose/DNA weight ratios required to achieve stability result in formulations that are not osmotically compatible with the subcutaneous (SC) or intramuscular (IM) injection of a typical dose of plasmid DNA. In an effort to reduce the formulation osmolality, dextrans possessing a range of molecular weights were investigated for their ability to serve as protectants. Dextran 3000 proved to be the most effective of the dextrans tested, and offered similar protection to sucrose on a weight basis. However, the advantage of employing this excipient is that the resulting osmolality is reduced by approximately 40% as compared to an equivalent weight of sucrose. Moreover, the use of dextran allows lyophilized vector preparations to be rehydrated to reduced volumes, essentially concentrating vectors prior to administration. Utilizing a combination of dextran 3000 and sucrose, we demonstrate that complexes of polyethylenimine (PEI) and DNA lyophilized at 0.1 mg/mL can be concentrated tenfold upon rehydration, resulting in an isotonic formulation containing 1 mg/mL DNA that can provide more realistic injection volumes for animal studies, and is compatible with clinical trials involving SC and IM injection. | ||||||||
| 6975 | 3.19 | 18271547 | 2008.08.20 | + | + | Biophysical characterization of nanoparticle-endothelial model cell membrane interactions. | Mol Pharm | |
| C Peetla, V Labhasetwar, | ||||||||
| Understanding the biophysical interactions of nanoparticles (NPs) with cell membranes is critical for developing effective nanocarrier systems for drug delivery applications. We developed an endothelial model cell membrane (EMM) using a mixture of lipids and Langmuir balance to study its interaction with NPs. Polystyrene NPs of different surface chemistry and sizes were used as a model nanomaterial, and changes in the membrane's surface pressure (SP) were used as a parameter to monitor its interactions with NPs. Aminated NPs (60 nm) increased SP, plain NPs reduced it, and carboxylated NPs of the same size had no effect. However, smaller NPs (20 nm) increased SP irrespective of surface chemistry, and serum did not influence their SP effect, whereas it masked the effect of larger (>60 nm) plain and carboxylated but not that of aminated NPs. Membranes formed with a single phospholipid showed a different pattern of interactions with NPs than that with EMM, signifying the need of using a mixture of lipids representing the respective cells/tissue of interest for a model membrane. The particular effect of NP characteristics on SP, determined using atomic force microscopy and pi- A (surface pressure-area) isotherm, can be explained on the basis of whether the interaction results in condensation of phospholipids (increase in SP) or their displacement from the interface into the subphase (decrease in SP), causing destabilization of the membrane. We conclude that NP characteristics significantly influence biophysical interactions with the membrane. Further, the molecular mechanism(s) of nanoparticle interactions with model membranes can be effectively used for optimizing the characteristics of nanomaterials for particular biological applications. | ||||||||
| 6976 | 3.19 | 17323398 | 2007.07.25 | + | + | Control and selectivity of photosensitized singlet oxygen production: challenges in complex biological systems. | Chembiochem | |
| E Cló, JW Snyder, PR Ogilby, KV Gothelf, | ||||||||
| Singlet molecular oxygen is a reactive oxygen species that plays an important role in a number of biological processes, both as a signalling agent and as an intermediate involved in oxidative degradation reactions. Singlet oxygen is commonly generated by the so-called photosensitization process wherein a light-absorbing molecule, the sensitizer, transfers its energy of excitation to ground-state oxygen to make singlet oxygen. This process forms the basis of photodynamic therapy, for example, where light, a sensitizer, and oxygen are used to initiate cell death and ultimately destroy undesired tissue. Although the photosensitized production of singlet oxygen has been studied and used in biologically pertinent systems for years, the photoinitiated behaviour is often indiscriminate and difficult to control. In this Concept, we discuss new ideas and results in which spatial and temporal control of photosensitized singlet oxygen production can be implemented through the incorporation of the sensitizer into a conjugate system that selectively responds to certain triggers or stimuli. | ||||||||
| 6977 | 3.19 | 15516745 | 2005.04.21 | + | + | Influence of the homogenisation procedure on the physicochemical properties of PLGA nanoparticles. | Chem Pharm Bull (Tokyo) | |
| J Vandervoort, K Yoncheva, A Ludwig, | ||||||||
| Pilocarpine HCl-loaded PLGA nanoparticles were prepared by emulsification solvent evaporation. Three different stabilisers, polyvinylalcohol (PVA), Carbopol and Poloxamer were used, as well as mixtures thereof. The influence of the homogenisation pressure and number of cycles on the properties of nanoparticles were studied. Particle size was shown to depend on the stabiliser used. An increase of the homogenisation pressure or the number of cycles resulted in a decrease in particle size. The zeta potential value was influenced mainly by the nature of the stabiliser. Particles stabilised with poloxamer or PVA showed a slightly negative zeta potential value, while samples stabilised with carbopol possessed a more negative zeta potential, which became less negative after homogenisation. Drug encapsulation depended strongly on the stabiliser used. The higher drug entrapment of the carbopol-stabilised particles could be explained by an electrostatic interaction between the negatively charged carboxyl groups of carbopol and the positively charged, protonated pilocarpine. The drug release patterns of the particles prepared were quite similar. Differences between the release patterns of the homogenised particles could be attributed both to differences in size as well as drug encapsulation. Turbidimetric measurements suggested an interaction between mucin and PLGA nanoparticles exclusively stabilised with Carbopol. | ||||||||
| 6978 | 3.19 | 14675841 | 2004.03.17 | + | + | Screening organic micropollutants in surface waters by SPE extraction and ecotoxicological testing. | Chemosphere | |
| S Galassi, L Guzzella, V Croce, | ||||||||
| Complex mixtures of toxic substances occurring in surface waters are difficult to characterise by chemical analyses because each compound occurs at a very low concentration and requires a specific analytical method to be identified. Ecotoxicological tests on water extracts can be used as a screening tool to evaluate quickly and simply the overall quality of a water body with regard to micropollutant contamination. In this work, a pre-concentration procedure based on solid-phase extraction (SPE), suitable for both biological testing and analytical determination, is proposed. The extraction procedure is an improved version of a methodology used to evaluate the toxicity of organic micropollutants occurring in surface waters. It offers the advantage of using disposable commercial cartridges, which are easier to manage than the columns prepared with macromolecular resins. Water extracts from two representative Italian rivers, characterised by a different gradient of potential contamination and prepared according to the new concentration techniques, are used. The acute toxicity of the water extracts is tested on Daphnia magna and the bioluminescence inhibition in Vibrio fischeri. Criteria based on the concentration factor (CF) are proposed for assessing the hazard to aquatic life due to the exposure to toxic substances in surface waters. The aim of hazard ranking is to focus analytical efforts towards those samples that show the highest toxic potential. | ||||||||
| 6979 | 3.19 | 15025948 | 2004.12.10 | + | + | Effects of acute gamma-hexachlorocyclohexane intoxication in relation to the redox regulation of nuclear factor-kappaB, cytokine gene expression, and liver injury in the rat. | Antioxid Redox Signal | |
| LA Videla, G Tapia, P Varela, P Cornejo, J Guerrero, Y Israel, V Fernández, | ||||||||
| gamma-Hexachlorocyclohexane-induced hepatotoxicity is associated with oxidative stress. We tested the hypothesis that gamma-hexachlorocyclohexane triggers the redox activation of nuclear factor-kappaB (NF-kappaB), leading to proinflammatory cytokine expression. Liver NF-kappaB activation (electrophoretic mobility shift assay), tumor necrosis factor-alpha (TNF-alpha) and interleukin-1alpha (IL-1alpha) mRNA expression (reverse transcription-polymerase chain reaction), and their serum levels (enzyme-linked immunosorbent assay) were measured at different times after gamma-hexachlorocyclohexane treatment (50 mg/kg). The relationship between these and hepatic O(2) uptake, glutathione and protein carbonyl levels, and sinusoidal lactate dehydrogenase (LDH) efflux in liver perfusion studies was determined. gamma-Hexachlorocyclohexane increased liver NF-kappaB DNA binding at 14-22 h after treatment, concomitantly with significant glutathione depletion and an increase in the rate of O(2) consumption, the content of protein carbonyls, and the sinusoidal LDH efflux. In these conditions, the expression of TNF-alpha and IL-1alpha is enhanced, with maximal increases in their respective mRNA content and serum levels of the cytokines being elicited at 18 h after gamma-hexachlorocyclohexane treatment. All these changes are suppressed by the administration of alpha-tocopherol (100 mg/kg) or the Kupffer cell inactivator gadolinium chloride (10 mg/kg) prior to gamma-hexachlorocyclohexane. gamma-Hexachlorocyclohexane-induced TNF-alpha levels in serum are suppressed by pretreatment with an antisense oligonucleotide (ASO TJU-2755; daily doses of 10 mg/kg for 2 days) targeting the primary transcript for the cytokine, whereas those of IL-1alpha are not modified. It is concluded that gamma-hexachlorocyclohexane-induced liver oxidative stress triggers the DNA binding activity of NF-kappaB, with the consequent increase in the expression of NF-kappaB-dependent genes for TNF-alpha and for IL-1alpha, factors that may mediate the hepatotoxicity of the insecticide. | ||||||||
| 6980 | 3.19 | 17154473 | 2007.02.20 | + | + | Characterization of (aminoethyl)chitin/DNA nanoparticle for gene delivery. | Biomacromolecules | |
| JY Je, YS Cho, SK Kim, | ||||||||
| Nonviral gene delivery systems have been increasingly proposed as a safer alternative to viral vehicles. In the present study, we synthesized water-soluble chitin by aminoalkylating onto chitin at the C-6 position, and its transfection efficiency was investigated. Aminoethyl-chitin (AEC) was complexed with DNA, and AEC/DNA nanoparticles were characterized. AEC/DNA nanoparticles showed good DNA binding ability, high protection of DNA from nuclease and serum, and low cytotoxicity. Mean particle size decreased from 367 to 290 nm and zeta potential increased from -4.58 to 22.87 mV when the AEC/DNA charge ratio (N/P) increased from 1.15 to 18.5. The transfection efficiency of AEC/DNA nanoparticles was investigated in a human embryonic kidney cell line (HEK293), and the results showed that AEC/DNA nanoparticles were much enhanced compare with naked DNA. | ||||||||
| 6981 | 3.18 | 12799113 | 2003.08.20 | + | + | Ionoregulatory disruption as the acute toxic mechanism for lead in the rainbow trout (Oncorhynchus mykiss). | Aquat Toxicol | |
| JT Rogers, JG Richards, CM Wood, | ||||||||
| The mechanism for acute toxicity of lead (Pb) in rainbow trout (Oncorhynchus mykiss) was investigated at Pb concentrations close to the 96 h LC50 of 1.0 mg dissolved Pb l(-1) (0.8-1.4, 95% C.I.) determined in dechlorinated Hamilton city tap water (from Lake Ontario, hardness=140 mg l(-1) CaCO(3)). Tissue Pb accumulation associated with death was highest in the gill, followed by kidney and liver. Significant ionoregulatory impacts were observed in adult rainbow trout (200-300 g) fitted with indwelling dorsal aortic catheters and exposed to 1.1+/-0.04 mg dissolved Pb l(-1). Decreased plasma [Ca(2+)], [Na(+)] and [Cl(-)] occurred after 48 h of exposure through to 120 h, with increases in plasma [Mg(2+)], ammonia, and cortisol. No marked changes in PaO(2), PaCO(2), pH, glucose, or hematological parameters were evident. Branchial Na(+)/K(+) ATPase activity in juvenile trout exposed to concentrations close to the 96 h LC50 was inhibited by approximately 40% after 48 h of Pb exposure. Calcium ion flux measurements using 45Ca as a radiotracer showed 65% inhibition of Ca(2+) influx after 0, 12, 24 or 48 h exposure to the 96 h LC50 concentration of Pb. There was also significant inhibition (40-50%) of both Na(+) and Cl(-) uptake, measured with 22Na and 36Cl simultaneously. We conclude that the mechanism of acute toxicity for Pb in rainbow trout occurs by ionoregulatory disruption rather than respiratory or acid/base distress at Pb concentrations close to the 96 h LC50 in moderately hard water. | ||||||||
| 6982 | 3.18 | 11996330 | 2002.12.12 | + | + | Progress in the development and use of ferrate(VI) salt as an oxidant and coagulant for water and wastewater treatment. | Water Res | |
| JQ Jiang, B Lloyd, | ||||||||
| This paper reviews the progress in preparing and using ferrate(VI) salt as an oxidant and coagulant for water and wastewater treatment. The literature revealed that due to its unique properties (viz. strong oxidizing potential and simultaneous generation of ferric coagulating species), ferrate(VI) salt can disinfect microorganisms, partially degrade and/or oxidise the organic and inorganic impurities, and remove suspended/colloidal particulate materials in a single dosing and mixing unit process. However, these findings have not yet lead to the full-scale application of ferrate(VI) in the water industry owing to difficulties associated with the relatively low yield of ferrate(VI), the instability of the chemical depending on its method of preparation, and the lack of adequate studies that have demonstrated its capabilities and advantages over existing water and wastewater treatment methods. Fundamental study is thus required to explore the new preparation methods focusing on increasing the production yield and product's stability and avoiding using hypochlorite or chlorine as the oxidant. Also, the application of ferrate(VI) in drinking water treatment has not been studied systematically and future work in this field is recommended. | ||||||||
| 6983 | 3.18 | 16137845 | 2006.01.05 | + | + | In vitro study of the pulmonary translocation of nanoparticles: a preliminary study. | Toxicol Lett | |
| J Geys, L Coenegrachts, J Vercammen, Y Engelborghs, A Nemmar, B Nemery, PH Hoet, | ||||||||
| Recent studies indicate that inhaled ultrafine particles can pass into the circulation. To study this translocation in an in vitro model three types of pulmonary epithelial cells were examined. The integrity of the cell monolayer was verified by measuring the transepithelial electrical resistance (TEER) and passage of sodium fluorescein. TEER was too low in A549 cells. In these preliminary experiments, TEER values of 1007+/-300 and 348+/-62 Omega cm2 were reached for the Calu-3 cell line, using permeable membranes of 0.4 and 3 microm pore size, respectively. Growing primary rat type II pneumocytes on 0.4 microm pores, a TEER value of 241+/-90 Omega cm2 was reached on day 5; on 3 microm pores, no acceptable high TEER value was obtained. Translocation studies were done using 46 nm fluorescent polystyrene particles. When incubating polystyrene particles on membranes without a cellular monolayer, significant translocation was only observed using 3 microm pores: 67.5% and 52.7% for carboxyl- and amine-modified particles, respectively. Only the Calu-3 cell line was used in an initial experiment to investigate the translocation: on 0.4 microm pores no translocation was observed, on 3 microm pores approximately 6% translocation was observed both for carboxyl- and amine-modified particles. | ||||||||
| 6984 | 3.18 | 18510429 | 2008.06.27 | + | + | Design opportunities for actively targeted nanoparticle vaccines. | Nanomed | |
| TM Fahmy, SL Demento, MJ Caplan, I Mellman, WM Saltzman, | ||||||||
| Vaccines for many infectious diseases are poorly developed or simply unavailable. There are significant technological and practical design issues that contribute to this problem; thus, a solution to the vaccine problem will require a systematic approach to test the multiple variables that are required to address each of the design challenges. Nanoparticle technology is an attractive methodology for optimizing vaccine development because design variables can be tested individually or in combination. The biology of individual components that constitute an effective vaccine is often well understood and may be integrated into particle design, affording optimal immune responses to specific pathogens. Here, we review technological variables and design parameters associated with creating modular nanoparticle vaccine systems that can be used as vectors to protect against disease. Variables, such as the material and size of the core matrix, surface modification for attaching targeting ligands and routes of administration, are discussed. Optimization of these variables is important for the development of nanoparticle-based vaccine systems against infectious diseases and cancer. | ||||||||
| 6985 | 3.18 | 15293351 | 2005.03.15 | + | + | Insights into the mechanism of magnetofection using PEI-based magnetofectins for gene transfer. | J Gene Med | |
| S Huth, J Lausier, SW Gersting, C Rudolph, C Plank, U Welsch, J Rosenecker, | ||||||||
| BACKGROUND: Gene delivery by the use of magnetic forces, so-called magnetofection, has been shown to enhance transfection efficiency of viral and non-viral systems up to several-hundred-fold. For this purpose gene carriers, such as polyethylenimine (PEI), are associated with superparamagnetic nanoparticles and complexed with plasmid DNA. Gene delivery is targeted by the application of a magnetic field. METHODS: To investigate the underlying mechanism, we studied the impact of the applied magnetic field on the transfection process of PEI-coated superparamagnetic iron oxide gene vectors (magnetofectins) using various cell lines. In particular, we addressed the question whether accelerated sedimentation of magnetofectins is the driving force or if the magnetic field itself directly influences the endocytic processing of the magnetofectins. The cellular uptake mechanism of magnetofectins was studied by electron microscopy and transfection experiments in the presence of various inhibitors that operate at different steps of endocytosis. RESULTS: In this study we could show that cellular uptake of magnetofectins proceeds obviously by endocytosis. Cellular uptake of magnetofectins behaves almost analogously as compared with PEI polyplexes. Besides unspecific endocytosis, apparently clathrin-dependent as well as caveolae-mediated endocytic uptake is involved. CONCLUSIONS: The magnetic field itself does not alter the uptake mechanism of magnetofectins. Obviously, the magnetic forces lead to an accelerated sedimentation of magnetofectins on the cell surface and do not directly affect the endocytic uptake mechanism. So further improvement of magnetic field application could lead to efficient targeting of gene expression into the desired organ and tissue in vivo. | ||||||||
| 6986 | 3.17 | 16768405 | 2006.11.08 | + | + | Effect of charge and molecular weight on the functionality of gelatin carriers for corneal endothelial cell therapy. | Biomacromolecules | |
| JY Lai, PL Lu, KH Chen, Y Tabata, GH Hsiue, | ||||||||
| Cell transplantation strategies usually involve the use of supporting carrier materials because of the soft and fragile nature of these grafts. In this work, a cell-adhesive gelatin hydrogel carrier was fabricated to deliver cultivated human corneal endothelial cell (HCEC) sheets, which were harvested from thermo-responsive poly(N-isopropylacrylamide) (PNIPAAm)-grafted culture surfaces. The carrier disks, consisting of gelatins with a different isoelectric point (IEP = 5.0 and 9.0) and a molecular weight (MW) ranging from 3 to 100 kDa, were subjected to 16.6 kGy gamma irradiation for sterilization. The effect of IEP and MW of the raw gelatins (i.e., before irradiation) on the functionality of sterilized disks was studied by determinations of mechanical property, water content, dissolution degree, and cytocompatibility. Irrespective of the IEP of raw gelatin, hydrogel disks prepared with high MW (100 kDa) exhibited a greater tensile strength, lower water content, and slower dissolution rate than those made of low MW gelatin (8 and 3 kDa). From the investigation of cellular responses to the disks, the negatively charged gelatin (IEP = 5.0) groups were more cytocompatible when compared with their positively charged counterparts (IEP = 9.0) at the same MW (100 kDa). Additionally, in the negatively charged gelatin groups, only a slight increase in pro-inflammatory cytokine expression was observed with increasing MW of gelatin from 3 to 100 kDa. It is concluded that the gamma-sterilized hydrogel disks made from raw gelatins (IEP = 5.0, MW = 100 kDa) with appropriate dissolution degree and acceptable cytocompatibility are capable of providing stable mechanical support, making these carriers promising candidates for intraocular delivery of cultivated HCEC sheets. | ||||||||
| 6987 | 3.17 | 11814705 | 2002.03.07 | + | + | The effects of glutathione and vitamin E on iron toxicity in isolated rat hepatocytes. | Toxicol Lett | |
| LM Milchak, J Douglas Bricker, | ||||||||
| This study examined the acute toxicity of ferrous sulfate on rat hepatocyte suspensions, the correlation between lipid peroxidation and cell death, and the roles of glutathione and vitamin E in protecting against iron toxicity. Incubation with ferrous sulfate for 2 h produced lipid peroxidation, but did not decrease cell viability in the hepatocytes. When diethyl maleate (DEM) was added to deplete cellular glutathione concentrations, ferrous sulfate treatment (2.0-5.0 mM) did cause cell death and lipid peroxidation developed more extensively, suggesting that iron-mediated hepatotoxicity is influenced by glutathione content. Reduced glutathione (GSH), N-acetylcysteine (NAC) and alpha-tocopherol (vitamin E), alone and in combination, were added to hepatocyte suspensions in an attempt to protect cells against iron-induced damage. In iron-DEM-treated cells, GSH and NAC treatment increased viability by 43 and 36%, respectively, but only the combination of the two agents reduced lipid peroxidation (53% decrease). Vitamin E treatment reduced lipid peroxidation by 39% and also increased cell viability by 12%. The greatest protection against iron-induced lipid peroxidation occurred with the combination of GSH, NAC and vitamin E, which reduced lipid peroxidation by 94% in iron-treated cells, and by 98% in iron-DEM-treated cells. However, this combination did not prevent iron-induced cell death, although it did increase viability by 18%. These results suggest that iron-induced cell death may not be dependent upon lipid peroxidation, at least in short-term exposures. The results also suggest an interaction between GSH and vitamin E in protecting against lipid peroxidation. | ||||||||
| 6988 | 3.17 | 17257668 | 2007.05.22 | + | + | Preparation, characterization and in vitro cytotoxicity of paclitaxel-loaded sterically stabilized solid lipid nanoparticles. | Biomaterials | |
| MK Lee, SJ Lim, CK Kim, | ||||||||
| In an effort to develop an alternative formulation of paclitaxel suitable for parenteral administration, paclitaxel-loaded sterically stabilized solid lipid nanoparticles (SLNs) were prepared, characterized and examined for in vitro cytotoxicity. The SLNs, comprising trimyristin (TM) as a solid lipid core and egg phosphatidylcholine and pegylated phospholipid as stabilizers, were prepared using a hot homogenization method. Regardless of paclitaxel loading, the particle sizes and zeta potentials of the prepared SLNs were around 200nm and -38mV, respectively, suggesting that they would be suitable as a parenteral formulation. Cryo-scanning electron microscopy showed that the SLNs were homogeneous and spherical in shape, while differential scanning calorimetry measurement of the melting peak revealed that the TM exists as a solid in our formulation. Paclitaxel was loaded to the solid cores at a w/w ratio of 6%. Gel column chromatography showed that paclitaxel co-eluted with the phospholipids, indicating that paclitaxel was incorporated in the SLNs. An in vitro drug release study showed that paclitaxel was released from the SLNs in a slow but time-dependent manner. Furthermore, treatment of the OVCAR-3 human ovarian cancer cell line and the MCF-7 breast cancer cell line with paclitaxel-loaded SLNs yielded cytotoxicities comparable to those of a commercially available Cremophor EL-based paclitaxel formulation. These results collectively suggest that our optimized SLN formulation may have a potential as alternative delivery system for parenteral administration of paclitaxel. | ||||||||
| 6989 | 3.16 | 12387753 | 2002.11.05 | + | + | Assessment of bioaccumulation, neuropathology, and neurobehavior following subchronic (90 days) inhalation in Sprague-Dawley rats exposed to manganese phosphate. | Toxicol Appl Pharmacol | |
| L Normandin, G Carrier, PF Gardiner, G Kennedy, AS Hazell, D Mergler, RF Butterworth, S Philippe, J Zayed, | ||||||||
| Methylcyclopentadienyl manganese tricarbonyl (MMT) is an organic manganese (Mn) compound added to unleaded gasoline. It has been suggested that the combustion products of MMT containing Mn, such as manganese phosphate, could cause neurological symptoms similar to Parkinson's disease in humans. The aim of this work was to investigate the exposure-response relationship of bioaccumulation, neuropathology, and neurobehavior following a subchronic inhalation exposure to manganese phosphate in Sprague-Dawley male rats. Rats were exposed 6 h/day, 5 days/week for 13 consecutive weeks at 30, 300, or 3000 microg/m(3) Mn phosphate and compared to controls. Some rats were implanted with chronic EMG electrodes in the gastrocnemius muscle of the hind limb to assess tremor at the end of Mn exposure. Spontaneous motor activity was measured for 36 h using a computerized autotrack system. Rats were then sacrificed by exsanguination and Mn level in different brain tissues and other organs was determined by instrumental neutron activation analysis. Neuronal cell counts were obtained by assessing the sum of five grid areas for the caudate/putamen and the sum of two adjacent areas for the globus pallidus. Increased manganese concentrations were observed in all tissues of the brain and was dose-dependent in olfactory bulb and caudate/putamen. In fact, beginning with the highest level of exposure (3000 microg/m(3)) and ending with the control group, Mn concentrations in the olfactory bulb were 2.47 vs 1.28 vs 0.77 vs 0.64 ppm (P < 0.05) while for the caudate/putamen, Mn concentrations were 1.06 vs 0.73 vs 0.62 vs 0.47 ppm (P < 0.05). The Mn concentrations in lung were also dose-dependent (10.30 vs 1.40 vs 0.42 vs 0.17 ppm; P < 0.05). No statistical difference was observed for loss of neurons in caudate/putamen and globus pallidus. Locomotor activity assessment and tremor assessment did not reveal in neurobehavioral changes between the groups. Our results reinforce the hypothesis that the olfactory bulb and caudate/putamen are the main brain tissues for Mn accumulation after subchronic inhalation exposure. | ||||||||
| 6990 | 3.16 | 17125367 | 2007.01.16 | + | + | Gold films deposited over regular arrays of polystyrene nanospheres as highly effective SERS substrates from visible to NIR. | J Phys Chem B | |
| L Baia, M Baia, J Popp, S Astilean, | ||||||||
| Gold nanostructured films of various thicknesses (15, 30, and 60 nm) are deposited over regular arrays of polystyrene nanospheres in an attempt to evaluate their potential as SERS-active substrates. Atomic force microscopy is used to topographically characterize the substrates as well as to ensure the thickness of the deposited gold films. The optical response of the prepared substrates recommends their use in SERS experiments with multiple laser lines from visible and NIR spectral domains. The assessment of the substrates' SERS activity is performed by using the 532, 633, and 830 nm excitation lines and different average enhancement factor (EF) values are obtained depending on the film thickness and employed laser line. The 60 nm gold nanostructured film generates the greatest local electromagnetic field confinement under NIR excitation and consequently gives rise to maximum SERS enhancement. The large tunability of surface plasmon excitation combined with the advantage of relatively high exhibited average EF values obtained under NIR excitation recommends these substrates as outstanding candidates for upcoming investigations of biological relevant molecules. | ||||||||
| 6991 | 3.16 | 12914033 | 2003.09.16 | + | + | Layer-by-layer growth of CdSe-based nanocrystal light-emitting diodes. | J Nanosci Nanotechnol | |
| J Lee, M Mathai, F Jain, F Papadimitrakopoulos, | ||||||||
| The partial exchange of surface-passivating trioctylphosphine oxide (TOPO) on CdSe and ZnS-clad CdSe (CdSe/ZnS) nanocrystals with primary amines was utilized to grow ultra-thin films of these nanocrystals under nonaqueous conditions. This growth was achieved using 1,12-diaminododecane in a layer-by-layer assembly format, where one of the amino groups binds with the nanocrystal surface and the other regenerates the interface for further binding of nanocrystals. The nature of the growth is dependent on the relative surface affinity between the TOPO and the primary amine toward the zinc or cadmium sites on the nanocrystals. Using this technique, high-quality luminescent films of these nanocrystals can be built with well-defined thicknesses. Electroluminescent devices have been fabricated using this methodology. | ||||||||
| 6992 | 3.16 | 17134180 | 2007.01.05 | + | + | Controllable synthesis and enhanced electrochemical properties of multifunctional Au(core)Co(3)O(4shell) nanocubes. | J Phys Chem B | |
| J Hu, Z Wen, Q Wang, X Yao, Q Zhang, J Zhou, J Li, | ||||||||
| Multifunctional Au(core)Co(3)O(4shell) nanocubes were synthesized through the introduction of chloroauric acid (HAuCl(4)) into a typical hydrothermal system after a solvothermal process was completed to form metastable Co(3)O(4) hollow nanospheres in the presence of sodium dodecyl benzenesulfonate (SDBS), which served as the surfactant. The strategy suggested that HAuCl(4) played a vital role in the shape transformation and core/shell structure formation, and the sizes of the nanocubes can be tunable through control of the acid concentration. The core/shell structure of the nanocubes was demonstrated by X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), and element analysis (EA) measurements. Moreover, Li ion battery measurement indicated that trace Au intercalation altered not only the size and shape of the Co(3)O(4) nanoparticles but also greatly increased their electrochemical properties. These multifunctional nanocubes will be not only helpful to study physical chemistry properties of magnetic nanocrystals but also are expected to find use in many fields such as biomolecular detection and analysis, sensor, electrochemistry, and Li ion batteries. | ||||||||
| 6993 | 3.15 | 12141487 | 2003.01.08 | + | + | Oxidation of amino groups by hydroxyl radicals in relation to the oxidation degree of the alpha-carbon. | Environ Sci Technol | |
| NK Leitner, P Berger, B Legube, | ||||||||
| Nitrogen organic compounds constitute a large class of aqueous pollutants. These compounds include not only azoic structures, nitrogen heterocycles, and nitrous groups but also amides and amines. This work consisted in studying the OH* induced oxidation of simple primary amines in dilute aqueous solution with special attention to mineralization of the nitrogen group as a function of the nature of the alpha-carbon. H2O2/UV and gamma-irradiation processes were used for the production of OH* radicals, and the molecules studied were one alpha-amino acid i.e., glycine (HOOCCH2NH2), and two primary amides i.e., acetamide (CH3CONH2) and oxamic acid (HOOCCONH2). It was shown that the oxidation of glycine leads to the formation of ammonia, whereas the acetamide molecule is first oxidized into oxamic acid ending in complete mineralization with production of nitrates. Reaction mechanisms are proposed which account for the observed inorganic nitrogen end product depending on the oxidation degree of the carbon atoms of the molecules. It follows that the present study will allow for prediction of the fate of nitrogen resulting from the oxidation of primary amino groups by OH* radicals. | ||||||||
| 6994 | 3.15 | 15104119 | 2004.05.04 | + | + | Protective effect of saponins derived from roots of Platycodon grandiflorum on tert-butyl hydroperoxide-induced oxidative hepatotoxicity. | Toxicol Lett | |
| KJ Lee, CY Choi, YC Chung, YS Kim, SY Ryu, SH Roh, HG Jeong, | ||||||||
| There is increasing evidence that oxidative stress is implicated in the pathogenesis of various diseases, including alcoholic liver injury. In the present work, we investigate the protective effects of the saponins isolated from the roots of Platycodon grandiflorum A. DC (Campanulaceae), Changkil saponins (CKS), on the tert-butyl hydroperoxide (t-BHP)-induced oxidative injury (hepatotoxicity) in cultured rat primary hepatocytes and in rat livers. CKS significantly reduced t-BHP-induced oxidative injuries in cultured rat hepatocytes, as determined by cell cytotoxicity, intracellular glutathione (GSH) content and lipid peroxidation in a dose-dependent manner. CKS provided good protection from the t-BHP-induced production of intracellular reactive oxygen species and DNA damage. In addition, CKS was able to quench 1,1-diphenyl-2-picrylhydrazyl (DPPH) free radicals and the superoxide radical. The in vivo study showed that the pretreatment with CKS prior to the administration of t-BHP significantly prevented the increase in the serum levels of hepatic enzyme markers (alanine aminotransferase and aspartate aminotransferase) and reduced oxidative stress, such as GSH content and lipid peroxidation, in the liver in a dose-dependent manner. These results support the anti-oxidative role of CKS, and demonstrate that CKS can scavenge oxygen free radicals and protect cells from oxidative stress. | ||||||||
| 6995 | 3.15 | 16714047 | 2007.04.10 | + | + | Quantitative structure-activity-activity and quantitative structure-activity investigations of human and rodent toxicity. | Chemosphere | |
| I Lessigiarska, AP Worth, TI Netzeva, JC Dearden, MT Cronin, | ||||||||
| Acute toxicity in different biological systems, including humans and rodents in vivo, and human and rodent cell lines in vitro, was investigated. The data were taken from the MEIC (Multicentre Evaluation of In Vitro Cytotoxicity) programme. Quantitative structure-activity-activity relationship (QSAAR) models were developed for the in vivo human and rodent toxicity including a combination of toxicity endpoint and structural descriptors as predictor variables. The human peak blood/serum LC(50) concentrations were most strongly related to human liver cell toxicity, while the in vivo oral human lethal doses were most closely related to the in vivo rodent LD(50) values. The QSAARs included structural descriptors encoding electronic/reactivity properties, presence of H-bond donors, compound aromaticity, and size/shape properties. Quantitative structure-activity relationships (QSARs) were derived by using structural descriptors accounting for molecular hydrophobicity, size and shape, and electronic properties. These models have the potential to provide useful insights in the development of non-animal (in vitro and in silico) methods for predicting human and mammalian toxicity. | ||||||||
| 6996 | 3.15 | 8304684 | 1994.03.07 | + | + | Relevance of occupational skin exposure. | Ann Occup Hyg | |
| V Fiserova-Bergerova, | ||||||||
| Dermal exposure gains in significance by the same token as permissible occupational inhalation exposures are lowered. The contribution of dermal absorption to the total dose absorbed during occupational exposure is apparent when dermal and pulmonary uptake rates are compared. Development of an experimental data base for evaluation and control of dermal exposure is hindered by: lack of suitable methods for measurement of dermal absorption in humans; interspecies differences in skin permeability; regional differences in absorption rates due to non-homogeneity of skin composition and perfusion rates over the body; possible skin damage induced by the chemical or dispersant; and exposure conditions in the workplace. In the absence of sufficient human data, theoretical models can provide satisfactory information on dermal absorption. It is advocated that the current practice of using acute dermal toxicity (LD50) as a criterion for warning on the potential of significant dermal absorption be replaced by a criterion based on comparison of the dermal penetration rate with the pulmonary uptake rate at inhalation exposures permissible in the workplace. | ||||||||
| 6997 | 3.15 | 15010134 | 2004.08.03 | + | + | All-trans-retinoic acid release from core-shell type nanoparticles of poly(epsilon-caprolactone)/poly(ethylene glycol) diblock copolymer. | Int J Pharm | |
| YI Jeong, MK Kang, HS Sun, SS Kang, HW Kim, KS Moon, KJ Lee, SH Kim, S Jung, | ||||||||
| Poly(epsilon-caprolactone)/poly(ethylene glycol) (abbreviated as CE) diblock copolymers were synthesized to make core-shell type nanoparticles for all-trans-retinoic acid (atRA). Fluorescence spectroscopy showed that critical association concentration (CAC) value decreased at higher MW of CE diblock copolymer. Drug loading characteristics were studied under various experimental conditions. Drug contents and loading efficiency increased as the MW of poly(epsilon-caprolactone) (PCL) block of CE and initial drug feeding amount increased. Solvent used and preparation method also affected drug contents and loading efficiency. According to 1H NMR using CDCl3 and D2O, specific peaks of the PCL block and drug appearing in CDCl3, disappeared at D2O, suggesting hydrophobic core with hydrophilic shell formed in water. atRA release was faster at smaller MW of copolymer and lower drug contents. Nanoparticles prepared in DMF showed faster release rate compared with those prepared in THF or acetone. Cytotoxicity of atRA against U87MG, U251MG and U343MG cell lines were increased by nanoencapsulation while empty nanoparticles of CE diblock copolymer were not significantly affected. | ||||||||
| 6998 | 3.15 | 9054638 | 1997.03.24 | + | + | Effects of particle exposure and particle-elicited inflammatory cells on mutation in rat alveolar epithelial cells. | Carcinogenesis | |
| KE Driscoll, LC Deyo, JM Carter, BW Howard, DG Hassenbein, TA Bertram, | ||||||||
| To investigate mechanisms underlying development of lung adenomas and carcinomas in rats exposed to poorly soluble particles the relationships between particle exposure, inflammation and mutagenesis in rat alveolar type II cells were characterized. Rats were exposed to saline or saline suspensions of 10 and 100 mg/kg of alpha-quartz, carbon black or titanium dioxide by intratracheal instillation. Fifteen months after exposure, bronchoalveolar lavage (BAL) cells were characterized as to number and type and lung histopathology performed. The alveolar type II cells were isolated and cultured in 6 thioguanine (6TG) containing media to select for mutation in the hprt gene. The potential contribution of lung inflammatory cells to in vivo mutagenic responses, were evaluated by co-culturing BAL cells with the rat alveolar epithelial cell line, RLE-6TN for 24 h and the RLE-6TN cells selected for 6TG resistance. Neutrophilic inflammation was detected in all rats exposed to 10 and 100 mg/kg of alpha-quartz and carbon black and 100 mg/kg titanium dioxide; epithelial hyperplasia was observed in rats exposed to 10 and 100 mg/kg of alpha-quartz and 100 mg/kg carbon black. Hprt mutation frequency was increased in alveolar type II cells from rats exposed to 10 and 100 mg/kg of alpha-quartz, 100 mg/kg carbon black and 100 mg/kg titanium dioxide. In vitro exposure of RLE-6TN cells to BAL cells from rats treated with 10 and 100 mg/kg of alpha-quartz or 100 mg/kg carbon black increased hprt mutant frequency. Both macrophage and neutrophil enriched BAL cell populations were mutagenic to RLE-6TN cells, however, the mutagenic activity appeared greatest for neutrophils. Addition of catalase to BAL cell:RLE-6TN co-cultures inhibited the increase in hprt mutation frequency. These studies demonstrate exposure of rats to doses of particles producing significant neutrophilic inflammation is associated with increased mutation in rat alveolar type II cells. The ability of particle-elicited macrophages and neutrophils to exert a mutagenic effect on epithelial cells in vitro supports a role for these inflammatory cells in the in vivo mutagenic effects of particle exposure. The inhibition of BAL cell-induced mutations by catalase implies a role for cell-derived oxidants in this response. | ||||||||
| 6999 | 3.15 | 15756696 | 2005.09.14 | + | + | Smart polyion complex micelles for targeted intracellular delivery of PEGylated antisense oligonucleotides containing acid-labile linkages. | Chembiochem | |
| M Oishi, F Nagatsugi, S Sasaki, Y Nagasaki, K Kataoka, | ||||||||
| A novel pH-sensitive and targetable antisense ODN delivery system based on multimolecular assembly into polyion complex (PIC) micelles of poly(L-lysine) (PLL) and a lactosylated poly(ethylene glycol)-antisense ODN conjugate (Lac-PEG-ODN) containing an acid-labile linkage (beta-propionate) between the PEG and ODN segments has been developed. The PIC micelles thus prepared had clustered lactose moieties on their peripheries and achieved a significant antisense effect against luciferase gene expression in HuH-7 cells (hepatoma cells), far more efficiently than that produced by the nonmicelle systems (ODN and Lac-PEG-ODN) alone, as well as by the lactose-free PIC micelle. In line with this pronounced antisense effect, the lactosylated PIC micelles showed better uptake than the lactose-free PIC micelles into HuH-7 cells; this suggested the involvement of an asialoglycoprotein (ASGP) receptor-mediated endocytosis process. Furthermore, a significant decrease in the antisense effect (27 % inhibition) was observed for a lactosylated PIC micelle without an acid-labile linkage (thiomaleimide linkage); this suggested the release of the active (free) antisense ODN molecules into the cellular interior in response to the pH decrease in the endosomal compartment is a key process in the antisense effect. Use of branched poly(ethylenimine) (B-PEI) instead of the PLL for PIC micellization led to a substantial decrease in the antisense effect, probably due to the buffer effect of the B-PEI in the endosome compartment, preventing the cleavage of the acid-labile linkage in the conjugate. The approach reported here is expected to be useful for the construction of smart intracellular delivery systems for antisense ODNs with therapeutic value. | ||||||||
| 7000 | 3.15 | 18587517 | 2008.11.17 | + | + | PM2.5 and associated polycyclic aromatic hydrocarbon and mutagenicity emissions from motorcycles. | Bull Environ Contam Toxicol | |
| HH Yang, SA Lee, DP Hsieh, MR Chao, CY Tung, | ||||||||
| In this study, PM(2.5) in diluted exhausts of motorcycles are collected and emission characteristics of PM(2.5)-associated polycyclic aromatic hydrocarbons (PAHs) and mutagenicities are investigated. The measured mutagenicity emission factors with metabolic activation for new fuel injection, used fuel injection, new carburetor and used carburetor motorcycles are 7.77 x 10(4), 1.18 x 10(5), 1.32 x 10(5) and 1.15 x 10(5) rev/km, respectively. The mutagenicity emission factors with metabolic activation are higher than the corresponding values without metabolic activation. The average PAH emission factors are 12.3, 16.3, 25.5 and 26.5 microg/km for new and used fuel-injection motorcycles, and new and used carburetor-operated motorcycles, respectively. The correlation coefficients between PAHs and mutagenicity emission factors are higher with metabolic activation (0.59) than that without metabolic activation (0.31). | ||||||||