Abstract  The purpose of this study was to investigate the effect of surface coating on the toxicity of silver nanoparticles (Ag NPs) soil. Earthworms (Eisenia fetida) were exposed to AgNO(3) and Ag NPs with similar size ranges coated with either polyvinylpyrrolidone (hydrophilic) or oleic acid (amphiphilic) during a standard sub-chronic reproduction toxicity test. No significant effects on growth or mortality were observed within any of the test treatments. Significant decreases in reproduction were seen in earthworms exposed to AgNO3, (94.21 mg kg(-1)) as well as earthworms exposed to Ag NPs with either coating (727.6 mg kg(-1) for oleic acid and 773.3 mg kg(-1) for polyvinylpyrrolidone). The concentrations of Ag NPs at which effects were observed are much higher than predicted concentrations of Ag NPs in sewage sludge amended soils; however, the concentrations at which adverse effects of AgNO(3) were observed are similar to the highest concentrations of Ag presently observed in sewage sludge in the United States. Earthworms accumulated Ag in a concentration-dependent manner from all Ag sources, with more Ag accumulating in tissues from AgNO(3) compared to earthorms exposed to equivalent concentrations of Ag NPs. No differences were observed in Ag accumulation or toxicity between earthworms exposed to Ag NPs with polyvinylpyrrolidone or oleic acid coatings.

Abstract  Two control and eight field-contaminated, metal-polluted soils were inoculated with Eisenia fetida (Savigny, 1826). Three, 7, 14, 21, 28 and 42 days after inoculation, earthworm survival, body weight, cocoon production and hatching rate were measured. Seventeen metals were analysed in E.fetida tissue, bulk soil and soil solution. Soil organic carbon content, texture, pH and cation exchange capacity were also measured. Cocoon production and hatching rate were more sensitive to adverse conditions than survival or weight change. Soil properties other than metal concentration impacted toxicity. The most toxic soils were organic-poor (1-10 g C kg(-1)), sandy soils (c. 74% sand), with intermediate metal concentrations (e.g. 7150-13, 100 mg Ph kg(-1), 2970-53,400 mg Zn kg(-1)). Significant relationships between soil properties and the life cycle parameters were determined. The best coefficients of correlation were generally found for texture, pH, Ag, Cd, Mg, Pb, Tl, and Zn both singularly and in multivariate regressions. Studies that use metal-amended artificial soils are not useful to predict toxicity of field multi-contaminated soils. (c) 2007 Elsevier Ltd. All rights reserved.

Abstract  The Models Knowledge Base is an inventory of the computational models that are developed, used or supported by EPA's offices. For each model, the Models Knowledge Base provides information on: its development; its conceptual basis, scientific detail and evaluation; technical requirements and how to use it; information on the its inputs and outputs; and directions for downloading it and links to further information.

Abstract  The Nanoparticle Occupational Safety and Health (NOSH) consortium of international industrial, academic, government and non-governmental organizations has focused research since the beginning of 2006 upon obtaining information on occupational safety and health associated with aerosol nanoparticles and workplace exposure monitoring and protocols. The three main technical goals of the consortium are 1) the development of a method to generate a well-characterized aerosol of solid nanoparticles and to measure aerosol behavior as a function of time; 2) the development of an air sampling method that can be used on a day-to-day basis toconduct worker exposure assessments in workplace settings; and 3) the ability to measure barrier efficiency of filter media with respect to specific engineered aerosol nanoparticles. Since one stated objective of the NOSH consortium is the wide dissemination of all findings, including nanoparticle synthesis methods, behavior of aerosol nanoparticles as a function of time, and barrier efficiency of commercially available filter media to aerosol nanoparticles, this talk will serve as one method to present data and findings from the consortium. This consortium continues work towards developing knowledge of workplace exposure monitoring capabilities and strategies through the design and development of portable aerosol monitoring instrumentation for conducting assessments of worker exposure to airborne engineered nanoparticles. Additionally the consortium continues to conduct studies to obtain knowledge of the barrier performance characteristics of commercially available filter media to aerosol nanoparticles. To accomplish these objectives, multiple aerosol synthesis and characterization systems have been designed and optimized to generate well-characterized aerosol nanoparticles of various chemistries in the 3 – 100 nm size range. These aerosol nanoparticles are transported to one of three enclosed aerosol test chambers in which the concentration and particle size distribution of the incoming aerosol nanoparticles are controlled to examine aerosol behavior as a function of time, including rate of dispersion, aggregation, and particle loss for both charged and uncharged aerosol nanoparticles. These well-controlled and well-characterized aerosol nanoparticle studies form the basis for the development of a portable nanoparticleaerosol monitoring instrument which will be field tested in a wide variety of workplace environments. Good handling techniques, which isolate the potential hazard at the source, and effective containment and control measures includingengineering controls, respiratory protective devices and protective clothing fabricsare generally considered to provide adequate protection for exposures to fine-sized particulates. However, prior to the consortium inception, the available methodologies utilized in industrial hygiene practices to measure particle exposures were typically not sufficiently sensitive to measure occupational or ambient nanoparticle aerosol concentrations, whether in terms of particle mass, particle numbers, or surface area. Through this effort, the consortium has developed the instrumentation and protocols required to assess the barrier effectiveness of filter media to charged and uncharged aerosol nanoparticles as a function of particle chemistry, particle size distributions, and number concentration. The consortium continues to focus on identifying appropriate filter media that can be used as effective barriers for aerosol nanoparticles and establishing a knowledge baseon determining specificationsfor using those filter media given a set of known properties about a specific nanoparticle aerosol.

Abstract  Silver nanoparticles (Ag NPs) have recently received much attention for their possible applications in biotechnology and life sciences. Ag NPs are of interest to defense and engineering programs for new material applications as well as for commercial purposes as an antimicrobial. However, little is known about the genotoxicity of Ag NPs following exposure to mammalian cells. This study was undertaken to examine the DNA damage response to polysaccharide surface functionalized (coated) and non-functionalized (uncoated) Ag NPs in two types of mammalian cells; mouse embryonic stem (mES) cells and mouse embryonic fibroblasts (MEF). Both types of Ag NPs up-regulated the cell cycle checkpoint protein p53 and DNA damage repair proteins Rad51 and phosphorylated-H2AX expression. Furthermore both of them induced cell death as measured by the annexin V protein expression and MTT assay. Our observations also suggested that the different surface chemistry of Ag NPs induce different DNA damage response: coated Ag NPs exhibited more severe damage than uncoated Ag NPs. The results suggest that polysaccharide coated particles are more individually distributed while agglomeration of the uncoated particles limits the surface area availability and access to membrane bound organelles.

Abstract  Primary cells are ideal for in vitro toxicity studies since they closely resemble tissue environment. Here, we report a detailed study on the in vitro interactions of 7-20 nm spherical silver nanoparticles (SNP) with primary fibroblasts and primary liver cells isolated from Swiss albino mice. The intended use of silver nanoparticles is in the form of a topical antimicrobial gel formulation for the treatment of burns and wounds. Upon exposure to SNP for 24 h, morphology of primary fibroblasts and primary liver cells remained unaltered up to 25 microg/mL and 100 microg/mL SNP, respectively, although with minor decrease in confluence. IC(50) values for primary fibroblasts and primary liver cells as revealed by XTT assay were 61 microg/mL and 449 microg/mL, respectively. Ultra-thin sections of primary cells exposed to 1/2 IC(50) SNP for 24 h, visualized under Transmission electron microscope showed the presence of dark, electron dense, spherical aggregates inside the mitochondria, and cytoplasm, probably representing the intracellular SNP. When the cells were challenged with approximately 1/2 IC(50) concentration of SNP (i.e. 30 microg/mL and 225 microg/mL for primary fibroblasts and primary liver cells, respectively), enhancement of GSH (approximately 1.2 fold) and depletion of lipid peroxidation (approximately 1.4 fold) were seen in primary fibroblasts which probably protect the cells from functional damage. In case of primary liver cells; increased levels of SOD ( approximately 1.4 fold) and GSH ( approximately 1.1 fold) as compared to unexposed cells were observed. Caspase-3 activity assay indicated that the SNP concentrations required for the onset of apoptosis were found to be much lower (3.12 microg/mL in primary fibroblasts, 12.5 microg/mL in primary liver cells) than the necrotic concentration (100 microg/mL in primary fibroblasts, 500 microg/mL in primary liver cells). These observations were confirmed by CLSM studies by exposure of cells to 1/2 IC(50) SNP (resulting in apoptosis) and 2 x IC(50)) cells (resulting in necrosis). These results clearly suggest that although silver nanoparticles seem to enter the eukaryotic cells, cellular antioxidant mechanisms protect the cells from possible oxidative damage. This property, in conjunction with the finding that primary cells possess much higher SNP tolerance than the concentration in the gel (approximately 20 microg/g), indicates preliminary safety of the formulation and warrants further study for possible human application.

Abstract  The environmental genotoxic behavior of silver nanoparticles (nanoAg) combined with the detergent cetylpyridine bromide (CPB) was examined in vitro. The experimental results showed that the genotoxicity of nanoAg itself is weak, but nanoAg shows obvious genotoxicity after combined with CPB. The combined materials have a strong coeffect on calf thymus DNA (ctDNA) at a concentration of 3.3 × 10−6 g mL−1 nanoAg and 6.0 × 10−6 mol L−1 CPB. After the addition of ctDNA to the nanoAg–CPB system, the particles are scattered and the diameter decreases, which indirectly reveal that nanoAg–CPB has genotoxicity.

Abstract  Ecological and toxicological aspects of silver (Ag) and silver salts in the environment are briefly summarized with an emphasis on natural resources. Elevated silver concentrations in biota occur in the vicinities of sewage outfalls, electroplating plants, mine waste sites, and silver-iodide seeded areas; in the United States, the photography industry is the major source of anthropogenic silver discharges into the biosphere. Silver and its compounds are not known to be mutagenic, teratogenic, or carcinogenic. Under normal routes of exposure, silver does not pose serious environmental health problems to humans at less than 50 ug total Ag/L drinking water or 10 ug total Ag/m3 air. Free silver ion, however, was lethal to representative species of sensitive aquatic plants, invertebrates, and teleosts at nominal water concentrations of 1.2 to 4.9 ug/L; sublethal effects were significant between 0.17 and 0.6 ug/L. Silver was harmful to poultry at concentrations as low as 1.8 mg total Ag/kg whole egg fresh weight by way of injection, 100 mg total Ag/L in drinking water, or 200 mg total Ag/kg in diets; sensitive mammals were adversely affected at total silver concentrations as low as 250 ug/L in drinking water, 6 mg/kg in diets, or 13.9 mg/kg whole body.

Abstract  Silver nanoparticles (nano-Ag) are potent and broad-spectrum antimicrobial agents. In this study, spherical nano-Ag (average diameter = 9.3 nm) particles were synthesized using a borohydride reduction method and the mode of their antibacterial action against E. coli was investigated by proteomic approaches (2-DE and MS identification), conducted in parallel to analyses involving solutions of Ag(+) ions. The proteomic data revealed that a short exposure of E. coli cells to antibacterial concentrations of nano-Ag resulted in an accumulation of envelope protein precursors, indicative of the dissipation of proton motive force. Consistent with these proteomic findings, nano-Ag were shown to destabilize the outer membrane, collapse the plasma membrane potential and deplete the levels of intracellular ATP. The mode of action of nano-Ag was also found to be similar to that of Ag(+) ions (e.g., Dibrov, P. et al, Antimicrob. Agents Chemother. 2002, 46, 2668-2670); however, the effective concentrations of nano-Ag and Ag(+) ions were at nanomolar and micromolar levels, respectively. Nano-Ag appear to be an efficient physicochemical system conferring antimicrobial silver activities.

Abstract  Nanotechnology is expected to open new avenues to fight and prevent disease using atomic scale tailoring of materials. Among the most promising nanomaterials with antibacterial properties are metallic nanoparticles, which exhibit increased chemical activity due to their large surface to volume ratios and crystallographic surface structure. The study of bactericidal nanomaterials is particularly timely considering the recent increase of new resistant strains of bacteria to the most potent antibiotics. This has promoted research in the well known activity of silver ions and silver-based compounds, including silver nanoparticles. The present work studies the effect of silver nanoparticles in the range of 1-100 nm on Gram-negative bacteria using high angle annular dark field (HAADF) scanning transmission electron microscopy (STEM). Our results indicate that the bactericidal properties of the nanoparticles are size dependent, since the only nanoparticles that present a direct interaction with the bacteria preferentially have a diameter of [?]1-10 nm.

Abstract  In this work we investigated the antibacterial properties of differently shaped silver nanoparticles against the gram-negative bacterium Escherichia coli, both in liquid systems and on agar plates. Energy-filtering transmission electron microscopy images revealed considerable changes in the cell membranes upon treatment, resulting in cell death. Truncated triangular silver nanoplates with a {111} lattice plane as the basal plane displayed the strongest biocidal action, compared with spherical and rod-shaped nanoparticles and with Ag+ (in the form of AgNO3). It is proposed that nanoscale size and the presence of a {111} plane combine to promote this biocidal property. To our knowledge, this is the first comparative study on the bactericidal properties of silver nanoparticles of different shapes, and our results demonstrate that silver nanoparticles undergo a shape-dependent interaction with the gram-negative organism E. coli.

Abstract  The antimicrobial activity of silver nanoparticles against E. coli was investigated as a model for Gram-negative bacteria. Bacteriological tests were performed in Luria?Bertani (LB) medium on solid agar plates and in liquid systems supplemented with different concentrations of nanosized silver particles. These particles were shown to be an effective bactericide. Scanning and transmission electron microscopy (SEM and TEM) were used to study the biocidal action of this nanoscale material. The results confirmed that the treated E. coli cells were damaged, showing formation of ?pits? in the cell wall of the bacteria, while the silver nanoparticles were found to accumulate in the bacterial membrane. A membrane with such a morphology exhibits a significant increase in permeability, resulting in death of the cell. These nontoxic nanomaterials, which can be prepared in a simple and cost-effective manner, may be suitable for the formulation of new types of bactericidal materials.

Abstract  The ATSDR toxicological profile succinctly characterizes the toxicologic and adverse health effects information for the hazardous substance described here. Each peer-reviewed profile identifies and reviews the key literature that describes a hazardous substance's toxicologic properties. Other pertinent literature is also presented, but is described in less detail than the key studies.

Abstract  Due to their small size, nanoparticles have distinct properties compared with the bulk form of the same materials. These properties are rapidly revolutionizing many areas of medicine and technology. Despite the remarkable speed of development of nanoscience, relatively little is known about the interaction of nanoscale objects with living systems. In a biological fluid, proteins associate with nanoparticles, and the amount and presentation of the proteins on the surface of the particles leads to an in vivo response. Proteins compete for the nanoparticle "surface," leading to a protein "corona" that largely defines the biological identity of the particle. Thus, knowledge of rates, affinities, and stoichiometries of protein association with, and dissociation from, nanoparticles is important for understanding the nature of the particle surface seen by the functional machinery of cells. Here we develop approaches to study these parameters and apply them to plasma and simple model systems, albumin and fibrinogen. A series of copolymer nanoparticles are used with variation of size and composition (hydrophobicity). We show that isothermal titration calorimetry is suitable for studying the affinity and stoichiometry of protein binding to nanoparticles. We determine the rates of protein association and dissociation using surface plasmon resonance technology with nanoparticles that are thiol-linked to gold, and through size exclusion chromatography of protein-nanoparticle mixtures. This method is less perturbing than centrifugation, and is developed into a systematic methodology to isolate nanoparticle-associated proteins. The kinetic and equilibrium binding properties depend on protein identity as well as particle surface characteristics and size.

Abstract  The antimicrobial effects of silver (Ag) ion or salts are well known, but the effects of Ag nanoparticles on microorganisms and antimicrobial mechanism have not been revealed clearly. Stable Ag nanoparticles were prepared and their shape and size distribution characterized by particle characterizer and transmission electron microscopic study. The antimicrobial activity of Ag nanoparticles was investigated against yeast, Escherichia coli, and Staphylococcus aureus. In these tests, Muller Hinton agar plates were used and Ag nanoparticles of various concentrations were supplemented in liquid systems. As results, yeast and E. coli were inhibited at the low concentration of Ag nanoparticles, whereas the growth-inhibitory effects on S. aureus were mild. The free-radical generation effect of Ag nanoparticles on microbial growth inhibition was investigated by electron spin resonance spectroscopy. These results suggest that Ag nanoparticles can be used as effective growth inhibitors in various microorganisms, making them applicable to diverse medical devices and antimicrobial control systems.

Abstract  This model calculates the deposition and clearance of monodisperse and polydisperse aerosols in the respiratory tract of rats, human adults and children (deposition only) for particles ranging from ultrafine (0.01 microns) to coarse (20 microns) sizes. The models are based upon single-path and multiple-path methods for tracking air flow and calculating aerosol deposition in the lung. The single-path method calculates deposition in a typical path per airway generation, while the multiple-path method calculates particle deposition in all airways of the lung and provides lobar-specific and airway-specific information. Within each airway, deposition is calculated using theoretically derived efficiencies for deposition by diffusion, sedimentation and impaction within the airway or airway bifurcation. Filtration of aerosols by the head (nose and mouth) is determined using empirical efficiency functions.

Abstract  A sensitive and rapid technique for directly measuring silver in blood, using electrothermal atomization atomic absorption spectrophotometry (ETAAS) is described. The method can be used to analyse precisely up to 40 blood samples a day in duplicate. Well-mixed, whole blood samples, collected in EDTA, were diluted 1 + 4 with a diluent containing 40 g l.-1 ammonium dihydrogen orthophosphate and 0.5 ml l.-1 Triton X-100. Aliquots of diluted blood were then analysed by ETAAS using wall atomization with a pyrolytically coated tube. The coefficient of variation for within-run precision was 4.55% at 10 micrograms 1.-1 and 5% at 25 micrograms 1.-1 Between-run variation, it was 4.1% at 25 micrograms l.-1 The analytical recovery for the method was 98% +/- 3% at both 8 and 30 micrograms 1. -1 The detection limit of the method was 0.1 microgram 1. -1, which was sufficiently sensitive to distinguish exposed from non-exposed individuals. Blood silver levels in unexposed subjects were found to be between < 0.1 and 0.2 micrograms 1. -1. Blood silver levels were determined in 98 occupationally exposed workers involved in bullion production, cutlery manufacture, chemical manufacture, jewelery production and silver reclamation. Blood silver levels ranged from 0.1 to 23 micrograms 1.-1, with some of the highest levels found in silver reclaimers.

Abstract  The rapid advancement of nanotechnology has created a vast array of engineered nanomaterials (ENMs) which have unique physical (size, shape, crystallinity, surface charge) and chemical (surface coating, elemental composition and solubility) attributes. These physicochemical properties of ENMs can produce chemical conditions to induce a pro-oxidant environment in the cells, causing an imbalanced cellular energy system dependent on redox potential and thereby leading to adverse biological consequences, ranging from the initiation of inflammatory pathways through to cell death. The present study was designed to evaluate size-dependent cellular interactions of known biologically active silver nanoparticles (NPs, Ag-15 nm, Ag-30 nm, and Ag-55 nm). Alveolar macrophages provide the first defense and were studied for their potential role in initiating oxidative stress. Cell exposure produced morphologically abnormal sizes and adherence characteristics with significant NP uptake at high doses after 24 h. Toxicity evaluations using mitochondrial and cell membrane viability along with reactive oxygen species (ROS) were performed. After 24 h of exposure, viability metrics significantly decreased with increasing dose (10-75 microg/mL) of Ag-15 nm and Ag-30 nm NPs. A more than 10-fold increase of ROS levels in cells exposed to 50 microg/mL Ag-15 nm suggests that the cytotoxicity of Ag-15 nm is likely to be mediated through oxidative stress. In addition, activation of the release of traditional inflammatory mediators were examined by measuring levels of cytokines/chemokines, including tumor necrosis factor (TNF-alpha), macrophage inhibitory protein (MIP-2), and interleukin-6 (IL-6), released into the culture media. After 24 h of exposure to Ag-15 nm nanoparticles, a significant inflammatory response was observed by the release of TNF-alpha, MIP-2, and IL-1beta. However, there was no detectable level of IL-6 upon exposure to silver nanoparticles. In summary, a size-dependent toxicity was produced by silver nanoparticles, and one predominant mechanism of toxicity was found to be largely mediated through oxidative stress.

Abstract  Mice were fed either 13 nm silver nanoparticles or 2–3.5 μm silver microparticles. The livers were then obtained after 3 days and subjected to a histopathological analysis. The nanoparticle-fed and microparticle-fed livers both exhibited lymphocyte infiltration in the histopathological analysis, suggesting the induction of inflammation. In vitro, a human hepatoma cell line (Huh-7) was treated with the same silver nanoparticles and microparticles. The mitochondrial activity and glutathione production were hardly affected. However, the DNA contents decreased 15% in the nanoparticle-treated cells and 10% in the microparticle-treated cell, suggesting a more potent induction of apoptosis by the nanoparticles. From a microarray analysis of the RNA from the livers of the nano- and micro-particle-fed mice, the expression of genes related to apoptosis and inflammation was found to be altered. These gene expression changes in the nanoparticle-treated livers lead to phenotypical changes, reflecting increased apoptosis and inflammation. The changes in the gene expression were confirmed by using a semi-quantitative RT-PCR.