Abstract  The widespread use of silver nanoparticles (Ag-NPs) in commercial products, especially textiles, will likely result in an unknown spread of Ag into the environment. The quantification and characterization of the Ag released from nano-Ag-products is an important parameter needed to predict the effect of Ag-NPs on the environment. The aim of this study was to determine the amount and the form of Ag released during washing from nine fabrics with different ways of silver incorporation into or onto the fibers. The effect of pH, surfactants, and oxidizing agents was evaluated. The results show that little dissolution of Ag-NPs occurs under conditions relevant to washing (pH 10) with dissolved concentrations 10 times lower than at pH 7. However, bleaching agents such as hydrogen peroxide or peracetic acid (formed by the perborate/TAED system) can greatly accelerate the dissolution of Ag. The amount and form of Ag released from the fabrics as ionic and particulate Ag depended on the type of Ag-incorporation into the textile. The percentage of the total silver emitted during one washing of the textiles varied considerably among products (from less than 1 to 45%). In the washing machine the majority of the Ag (at least 50% but mostly >75%) was released in the size fraction >450 nm, indicating the dominant role of mechanical stress. A conventional silver textile did not show any significant difference in the size distribution of the released silver compared to many of the textiles containing nano-Ag. These results have important implications for the risk assessment of Ag-textiles and also for environmental fate studies of nano-Ag, because they show that under conditions relevant to washing, primarily coarse Ag-containing particles are released.

Abstract  Research has demonstrated that metallic nanoparticles produce toxicity in aquatic organisms that is due largely to effects of particulates as opposed to release of dissolved ions. The present research examined the interplay of nanoparticle composition and dissolution on response of the zebrafish gill following exposure to toxic (nanocopper or nanosilver) or nontoxic (nano-TiO2) nanometals. Female zebrafish were exposed to 48-h no observable effects concentration of nanocopper and nanosilver or to soluble Cu and Ag that matched the concentration of dissolved metals released during nanoparticle exposure. Both nanocopper and nanosilver exposures increased metal content associated with gill tissue, though silver concentrations were much higher following nanosilver exposures suggesting that intact silver nanoparticles are associated with the gill. Morphological and transcriptional responses of the gills differed among various nanomaterials and between nanoparticulate and soluble species. Nanocopper increased mean gill filament width by three to fourfold between 24 and 48 h, whereas nanosilver did not alter gill filament width at either time point. Global gene expression analysis demonstrates that the exposure to each nanometal or soluble metal produces a distinct gene expression profile at both 24 and 48 h, suggesting that each exposure is producing biological response by a different mechanism. The differences in responses among the exposures indicates that each particle is having a distinct biological effect that does not appear to be driven solely by release of soluble metal ions into the water column. Based on these results, care should be taken when inferring toxicity of nanomaterials from data on a different material.

Abstract  Exposure to elevated waterborne silver as AgNO3 (4.07 µM=448 µg l-1) in seawater resulted in osmoregulatory disturbance in the lemon sole (Parophrys vetulus). The main effects were increased plasma Na+ and Cl- concentrations which translated into increased plasma osmolality. Plasma Mg2+ levels were also slightly increased after 96 h exposure. Using radio-isotopic flux measurements, a 50% reduction in branchial unidirectional Na+ extrusion was observed after 48 h silver exposure. By applying an intestinal perfusion approach, we were able to separate and thus quantify the intestinal contribution to the observed silver-induced physiological disturbance and internal silver accumulation. This analysis revealed that the intestinal contribution to silver-induced ionoregulatory toxicity was as high as 50-60%. In marked contrast, internal silver accumulation (in liver and kidney) was found to be derived exclusively from uptake across the gills. Drinking of silver-contaminated seawater resulted in substantial silver accumulation in the intestinal tissue (but apparently not silver uptake across the intestine), which probably explains the intestinal contribution to silver-induced physiological disturbance.

Abstract  Nanosilver has well-known antibacterial properties, and is widely used in daily life as various medical and general products. In comparison with silver ion, there is serious lacking of information concerning the biological effects of nanoAg. In this study, we observed the cytotoxic effect of nanoAg in HeLa cells. The nanoAg-induced cytotoxicity was lower than that of AgNO3, used as a silver ion source. Apoptosis evaluated by flowcytometric analysis was associated with this cell death. Further, the expressions of ho-1 and mt-2A, well-known oxidative stress-related genes, were up-regulated by nanoAg treatment. Our results showed that nanoAg possesses the potential for cytotoxicity, therefore, in the case of exposure at high concentrations, we should consider to protect from nanoAg-induced toxicity.

Abstract  We examined the influence of speciation on the kinetics of silver uptake and depuration in the gills of two freshwater fish, the rainbow trout (Oncorhynchus mykiss) which has high branchial Na+ and Cl− uptake rates and is relatively sensitive to silver, and the European eel (Anguilla anguilla, yellow stage) which has low ion uptake rates and is relatively resistant to silver. Fish previously acclimated to the appropriate chloride level were exposed to 110mAgNO3 (1.3 μg l−1, sublethal) for 24 h in synthetic softwater with either low (10 μM) or high (1200 μM) chloride concentration, and then followed over a subsequent 67-day post-exposure period in silver-free water of the same chloride content. The exposures were therefore mainly to the free ion, Ag+ in the low chloride water versus mainly to the neutral aqueous complex, AgClaq in the high chloride water. In trout, but not in eel, water chloride is known to protect against physiological disturbances and toxicity caused by Ag+. In both fish species, at both chloride levels, silver uptake exhibited complex kinetics. Gill silver loading occurred slowly until 6 h, then rose greatly to a peak at 12 h, followed by significant net depuration thereafter during continued exposure. By 24 h, net gill loading was three- to fivefold greater from AgClaq than from Ag+ exposure in both species, and threefold greater in trout than in eel under both conditions, with trout holding a lower fraction of the whole body burden in their gills. During the post-exposure period, depuration of silver from the gills occurred rapidly in trout, but very slowly in eel, such that gill silver burdens were greater in eel throughout the 67-day period on both an absolute and relative basis (e.g. 35% of whole body burden in eel versus <3% in trout at day 8). The kinetics of depuration were described by two phase exponential models, with break points between the fast and slow phases at 1 and 15 days for trout and eel, respectively. We conclude that speciation affects not only uptake rates but also the kinetics of depuration. When silver is loaded from AgClaq it is clearly more labile than from Ag+ exposures, with 1.6–1.8-fold greater loss rates during the fast phases in both species. Differences in branchial silver uptake between eel and trout correlate well with differences in acute toxicity, but are not as large as differences in ion uptake rates. The complex time-dependent patterns of gill loading, and the higher loading from AgClaq than from Ag+, mean that gill total silver burden is not an appropriate endpoint for biotic ligand modelling.

Abstract  To fully assess the impact of pollutant releases into the environment, it is necessary to determine both the concentration of chemicals accumulating in biota and the biological effects they give rise to. Owing to time, expertise, and cost constraints, this is, however, rarely achieved. Here, quick, simple to perform, and inexpensive biomarkers and chemical immunoassays were combined in a rapid assessment approach to measure exposure to and effects of organic and metal pollutants on the ribbed mussel (Geukensia demmissa) from New Bedford Harbor, MA. Significant differences in polychlorinated biphenyl (PCB) and polyaromatic hydrocarbon (PAH) tissue residue concentrations were detected among sites using RaPID immunoassay. Selected analyses were verified using GC/MS. No significant differences were observed in metal concentrations (Cu, Cd, Pb, As, Hg, Ni) throughout the area. While causality cannot be attributed, multivariate canonical correlation analysis indicated that PCB and PAH concentrations were strongly associated with the induction of biomarkers of genotoxicity (micronucleus formation), immunotoxicity (spontaneous cytotoxicity), and physiological impairment (heart rate). It is concluded thatthe incorporation of chemical immunoassays with biological monitoring tools into routine management procedures is clearly viable and valuable as a means of identifying toxic impacts of pollutants on biota in situ.

Abstract  Unique electronic and chemical properties of metal nanoparticles have drawn the attention of chemists, physicists, biologists, and engineers who wish to use them for the development of new generation nanodevices. Metal nanoparticles such as gold and silver show noticeable photoactivity under UV-visible irradiation as is evident from the photoinduced fusion and fragmentation processes. Binding a photoactive molecule (e.g., pyrene) to metal nanoparticle enhances the photochemical activity and renders the organic-inorganic hybrid nanoassemblies suitable for light-harvesting and optoelectronic alications. The nature of charge-transfer interaction of fluorophore with gold surface dictates the pathways with which the excited-state deactivates. Obtaining insight into energy and electron-transfer processes is important to improve the charge separation efficiencies in metal-fluorophore nanoassemblies and photocatalytic activity of metal-semiconductor composites.

Abstract  This paper describes a general approach that generates nanoscale hollow structures of metals by reacting solutions of appropriate salt solutions with solid templates of a more reactive metal. Typical examples include Au3+, Pt2+, and Pd2+ salts and nanoparticles or nanowires of silver. The morphology, void space, and wall thickness of these hollow structures are all determined by the solid templates, which are completely converted into soluble species during the replacement reaction. Both electron microscopy and diffraction studies indicate that single crystalline hollow structures of metals can also be obtained when the templates are single crystals. These metallic hollow structures, having well-controlled sizes and shapes, are expected to find use in a number of applications that involve nanoscale encapsulation, drug delivery, plasmon photonics, and calorimetric sensing.

Abstract  Background: Studies in monkeys with intranasally instilled gold ultrafine particles (UFPs; < 100 nm) and in rats with inhaled carbon UFPs suggested that solid UFPs deposited in the nose travel along the olfactory nerve to the olfactory bulb. Methods: To determine if olfactory translocation occurs for other solid metal UFPs and assess potential health effects, we exposed groups of rats to manganese (Mn) oxide UFPs (30 nm; ~ 500 μg/m3) with either both nostrils patent or the right nostril occluded. We analyzed Mn in lung, liver, olfactory bulb, and other brain regions, and we performed gene and protein analyses. Results: After 12 days of exposure with both nostrils patent, Mn concentrations in the olfactory bulb increased 3.5-fold, whereas lung Mn concentrations doubled; there were also increases in striatum, frontal cortex, and cerebellum. Lung lavage analysis showed no indications of lung inflammation, whereas increases in olfactory bulb tumor necrosis factor-α mRNA (~ 8-fold) and protein (~ 30-fold) were found after 11 days of exposure and, to a lesser degree, in other brain regions with increased Mn levels. Macrophage inflammatory protein-2, glial fibrillary acidic protein, and neuronal cell adhesion molecule mRNA were also increased in olfactory bulb. With the right nostril occluded for a 2-day exposure, Mn accumulated only in the left olfactory bulb. Solubilization of the Mn oxide UFPs was < 1.5% per day. Conclusions: We conclude that the olfactory neuronal pathway is efficient for translocating inhaled Mn oxide as solid UFPs to the central nervous system and that this can result in inflammatory changes. We suggest that despite differences between human and rodent olfactory systems, this pathway is relevant in humans.

Abstract  Nanotechnology may yield a plethora of beneficial applications, but it can also be expected to present risks. The challenge is to anticipate and reduce environmental and health risks or, at a minimum, identify and deal with such threats once they begin to become evident. Past experience, particularly with the fuel additive MTBE(methyl tertiary butyl ether), provides valuable guidance on how to assess the potential risks of nanotechnology using a comprehensive environmental assessment approach, which combines a product life-cycle perspective with the risk assessment paradigm. This systematic approach can serve not only to guide the development of a research strategy for assessing the risks of nanotechnology but possibly even help avert unintended consequences of nanotechnology.

Abstract  This draft document presents two case studies of nanoscale titanium dioxide (nano-TiO2) used (1) to remove arsenic from drinking water and (2) as an active ingredient in topical sunscreen. The draft case studies are organized around a comprehensive environmental assessment approach that combines a product life cycle framework with the risk assessment paradigm. The document does not draw conclusions about potential risks. Rather, the case studies are intended to help identify what needs to be known in order to conduct a comprehensive environmental assessment of the potential risks related to nano-TiO2. This draft document is part of a process that will inform the development of EPA?s research strategy to support nanomaterial risk assessments.

Abstract  1. Isolated, non-identified neurons were voltage clamped using the internal perfusion technique. 2. Ions of Ag+ (1-100-mu-M) introduced into the bathing solution activated a steady-state inward current (I(Ag)) in the soma. The effect of Ag+ was reversible when the concentration of Ag+ was less than 75-mu-M or the time of alication was shorter than 10 min. 3. I(Ag) was observed both in the presence and absence of Na+ ions in the extracellular saline. It could also be activated when Cs+ ions were substituted for Na+ ions. 4. The current-voltage characteristics were linear in the voltage range - 100 to 0 mV. The revrsal potential in control saline was an average of 1.19 +/- 5.1 mV. 5. The application of Ag+ ions induces an elevation of intracellular free Ca2+ concentration by 10-20 times in both Ca2+-containing and Ca2+-free extracellular salines, as revealed by Fura-2 measurements. 6. Agents that increase the intracellular free Ca2+ concentration ([Ca2+]i), like thymol, caffeine and dinitrophenol, increased the amplitude of I(Ag). The effect was additive. Ruthenium Red, which blocks the release of Ca2+ from intracellular stores, decreased the Ag+ effect. 7. It is concluded that extracellularly applied Ag+ ions increase the cytoplasmic free Ca2+ concentration, which in turn activates non-specific cationic channels. 8. Ag+ ions in 1-10-mu-M concentration were able to decrease the voltage-activated Ca2+ current amplitude. This decrease, however, was due to the increase of [Ca2+]i which caused Ca2+-dependent inactivation.

Abstract  A novel biological method for the synthesis of silver nanoparticles using the fungus Verticillium is reported. Exposure of the fungal biomass to aqueous Ag+ ions resulted in the intracellular reduction of the metal ions and formation of silver nanoparticles of dimensions 25 ± 12 nm. Electron microscopy analysis of thin sections of the fungal cells indicated that the silver particles were formed below the cell wall surface, possibly due to reduction of the metal ions by enzymes present in the cell wall membrane. The metal ions were not toxic to the fungal cells and the cells continued to multiply after biosynthesis of the silver nanoparticles.

Abstract  A key element of any nanomaterial toxicity screening strategy is a detailed and comprehensive physicochemical characterization of the test material being studied. This is a critical factor for correlating the nanoparticle surface characteristics with any measured biological/toxicological responses, as well as to provide an adequate reference point for comparing toxicity results with the hazard-based findings of other investigators. Moreover, when hazard or risk-based evaluations are made on a particular nanomaterial (based on a variety of studies), it is important to ensure that the nanoparticle-types are identical or very similar in composition. This can only be accomplished if rigorous characterization is conducted. In the absence of an adequate assessment of the physical characteristics, it is easy to draw general conclusions on nanoparticle-types which may have similar chemical compositions but, in fact, have different sizes, shapes, crystal structures, surface coatings, and surface reactivity characteristics. The determination of nanomaterial physicochemical properties is vitally important to nanomedicinal applications in that the fate, accumulation, and transport of nanomaterials through the body over time may be predicted based on specific surface characteristics.

Abstract  Rarely observed nanoparticle dissolution rate data have been collected and explained for an environmentally and industrially relevant nanomaterial (PbS, the mineral galena) as a function of its particle size and aggregation state using high-resolution transmission electron microscopy (HRTEM) and solution analysis. Under identical anoxic acidic conditions (pH 3 HCl), it has been determined that the dissolution rate of PbS galena varies by at least 1 order of magnitude simply as a function of particle size, and also due to the aggregation state of the particles (dissolution rates measured are 4.4 x 10(-9) mol m(-2) s(-1) for dispersed 14 nm nanocrystals; 7.7 x 10(-10) mol m(-2) s(-1) for dispersed 3.1 microm microcrystals; and 4.7 x 10(-10) mol m(-2) s(-1) for aggregated 14 nm nanocrystals). The dissolution rate difference between galena microparticles and nanoparticles is due to differences in nanotopography and the crystallographic faces present. Aggregate vs. dispersed dissolution rates are related to transport inhibition in the observed highly confined spaces between densely packed, aggregated nanocrystals, where self-diffusion coefficients of water and ions decrease dramatically. This study shows that factors at the nanometer scale significantly influence the release rate of aqueous, highly toxic and bioavailable Pb in natural or industrial environments during galena dissolution.

Abstract  To investigate the effect of pH on nanoparticle aggregation and transport in porous media, we quantified nanoparticle transport in two-dimensional structures. Titania was used as a model compound to explore the effects of surface potential on particle mobility in the subsurface. Results show that pH, and therefore, surface potential and aggregate size, dominate nanoparticle interactions with each other and surfaces. In each solution, nanoparticle aggregate size distributions were bimodal or trimodal, and aggregate sizes increased as the pH approached the pH of the point of zero charge (pHzpc). Over 80% of suspended particles and aggregates were mobile over the pH range of 1-12, except close to the pHzpc of the surfaces, where the particles are highly aggregated. The effect of pH on transport is not symmetric around the pHzpc of the particles due to charging of the channel surfaces. However, transport speed of nanoparticle aggregates did not vary with pH. The surface element integration technique, which takes into account the effect of curvature of particles on interaction energy, was used to evaluate the ability of theory to predict nanoparticle transport.

Abstract  This paper describes the issues relating to the measurement of nanoparticle size, shape and dispersion when evaluating the toxicity of nanoparticles. Complete characterization of these materials includes much more than size, size distribution and shape; nonetheless, these attributes are usually the essential foundation. The measurement of particle size, particularly at scales of 100 nm or less, can be challenging under the best of conditions. Measurements that are routine in the laboratory setting become even more difficult when made under the physiological conditions relevant to toxicity studies, where the environment of the particles can be quite complex. Passive and active cellular responses, as well as the presence of a variety of nano-scale biological structures, often complicate the collection and interpretation of size and shape data. In this paper, we highlight several of the common issues faced when characterizing nanoparticles for toxicity testing and suggest general protocols to address these problems.

Abstract  Little is known about the impact manufactured nanoparticles will have on aquatic organisms. Previously, we demonstrated that toxicity differs with nanoparticle type and preparation and observed behavioral changes upon exposure to the more lethal nanoparticle suspensions. In this experiment, we quantified these behavioral and physiological responses of Daphnia magna at sublethal nanoparticle concentrations. Titanium dioxide (TiO2) and fullerenes (nano-C60) were chosen for their potential use in technology. Other studies suggest that addition of functional groups to particles can affect their toxicity to cell cultures, but it is unknown if the same is true at the whole organism level. Therefore, a fullerene derivative, C60HxC70Hx, was also used to examine how functional groups affect Daphnia response. Using a high-speed camera, we quantified several behavior and physiological parameters including hopping frequency, feeding appendage and postabdominal curling movement, and heart rate. Nano-C60 was the only suspension to cause a significant change in heart rate. Exposure to both nano-C60 and C60HxC70Hx suspensions caused hopping frequency and appendage movement to increase. These results are associated with increased risk of predation and reproductive decline. They indicate that certain nanoparticle types may have impacts on population and food web dynamics in aquatic systems.

Abstract  We have adapted an "in vitro" toxicity test using zebrafish embryos for a toxicogenomics approach. Our goal is to develop a rapid toxicity assay for nanoparticles to be used in food and other applications. We incubated fertilized fish eggs for 48 h in the presence of a solution of purified MWCNT (1 ppb to 10 ppm) or with nanosilver solutions (1 ppb to 5 ppm). We could not detect effects on development or timing. We have used quantitative RT-PCR to analyze the expression patterns of Cyp1A1, Ahr2, Cpt1, iNOS, Ncf1, NudT1, c/EBP- and MafT. These genes are involved in detoxification patterns, in the protection against oxidative stress or code for regulatory factors involved in the immune response. At these concentrations, nanosilver had clear effects on the expression of most of the genes in a dose dependant manner. Induction was maximum in the case of regulatory factors. On the contrary, changes in gene expression induced by MWCNTs were much lower, suggesting a reduced toxicity at the tested concentrations.

Abstract  This report consists of charts of toxic pollutants with the recommended water quality criteria listed for such things as freshwater, saltwater, human consumption, etc.