Sulfidation of silver nanoparticles: natural antidote to their toxicity.
15 Nov 2013-Environmental Science & Technology (American Chemical Society)-Vol. 47, Iss: 23, pp 13440-13448
TL;DR: It is suggested that even partial sulfidation of AgNP will decrease the toxicity of AgNPs relative to their pristine counterparts, and the presence of chloride in the exposure media strongly affects the toxicity results by affecting Ag speciation.
Abstract: Nanomaterials are highly dynamic in biological and environmental media. A critical need for advancing environmental health and safety research for nanomaterials is to identify physical and chemical transformations that affect the nanomaterial properties and their toxicity. Silver nanoparticles, one of the most toxic and well-studied nanomaterials, readily react with sulfide to form Ag(0)/Ag2S core–shell particles. Here, we show that sulfidation decreased silver nanoparticle toxicity to four diverse types of aquatic and terrestrial eukaryotic organisms (Danio rerio (zebrafish), Fundulus heteroclitus (killifish), Caenorhabditis elegans (nematode worm), and the aquatic plant Lemna minuta (least duckweed)). Toxicity reduction, which was dramatic in killifish and duckweed even for low extents of sulfidation (about 2 mol % S), is primarily associated with a decrease in Ag+ concentration after sulfidation due to the lower solubility of Ag2S relative to elemental Ag (Ag0). These results suggest that even partial ...
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Cites background from "Sulfidation of silver nanoparticles..."
...found that even a very low degree of sulfidation of AgNPs can result in a significant decrease in their toxicity because of the lower solubility of silver sulfide [37]....
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University of South Carolina1, Commonwealth Scientific and Industrial Research Organisation2, Rice University3, United States Geological Survey4, University of Plymouth5, University of Adelaide6, University of Florida7, ETH Zurich8, École Polytechnique Fédérale de Lausanne9, Swiss Federal Institute of Aquatic Science and Technology10
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References
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TL;DR: A series of stages for development of the embryo of the zebrafish, Danio (Brachydanio) rerio is described, providing for flexibility and continued evolution of the staging series as the authors learn more about development in this species.
Abstract: We describe a series of stages for development of the embryo of the zebrafish, Danio (Brachydanio) rerio. We define seven broad periods of embryogenesis--the zygote, cleavage, blastula, gastrula, segmentation, pharyngula, and hatching periods. These divisions highlight the changing spectrum of major developmental processes that occur during the first 3 days after fertilization, and we review some of what is known about morphogenesis and other significant events that occur during each of the periods. Stages subdivide the periods. Stages are named, not numbered as in most other series, providing for flexibility and continued evolution of the staging series as we learn more about development in this species. The stages, and their names, are based on morphological features, generally readily identified by examination of the live embryo with the dissecting stereomicroscope. The descriptions also fully utilize the optical transparancy of the live embryo, which provides for visibility of even very deep structures when the embryo is examined with the compound microscope and Nomarski interference contrast illumination. Photomicrographs and composite camera lucida line drawings characterize the stages pictorially. Other figures chart the development of distinctive characters used as staging aid signposts.
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TL;DR: 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.
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TL;DR: The 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.
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TL;DR: The results of this study indicate that risks to aquatic organisms may currently emanate from nano- Ag, nano-TiO(2), and nano-ZnO in sewage treatment effluents for all considered regions and for nano-Ag in surface waters.
Abstract: Engineered nanomaterials (ENM) are already used in many products and consequently released into environmental compartments. In this study, we calculated predicted environmental concentrations (PEC) based on a probabilistic material flow analysis from a life-cycle perspective of ENM-containing products. We modeled nano-TiO2, nano-ZnO, nano-Ag, carbon nanotubes (CNT), and fullerenes for the U.S., Europe and Switzerland. The environmental concentrations were calculated as probabilistic density functions and were compared to data from ecotoxicological studies. The simulated modes (most frequent values) range from 0.003 ng L−1 (fullerenes) to 21 ng L−1 (nano-TiO2) for surface waters and from 4 ng L−1 (fullerenes) to 4 μg L−1 (nano-TiO2) for sewage treatment effluents. For Europe and the U.S., the annual increase of ENMs on sludge-treated soil ranges from 1 ng kg−1 for fullerenes to 89 μg kg−1 for nano-TiO2. The results of this study indicate that risks to aquatic organisms may currently emanate from nano-Ag, n...
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TL;DR: This work suggests that AgNP morphological properties known to affect antimicrobial activity are indirect effectors that primarily influence Ag(+) release, and antibacterial activity could be controlled by modulating Ag(+ release, possibly through manipulation of oxygen availability, particle size, shape, and/or type of coating.
Abstract: For nearly a decade, researchers have debated the mechanisms by which AgNPs exert toxicity to bacteria and other organisms. The most elusive question has been whether the AgNPs exert direct “particle-specific” effects beyond the known antimicrobial activity of released silver ions (Ag+). Here, we infer that Ag+ is the definitive molecular toxicant. We rule out direct particle-specific biological effects by showing the lack of toxicity of AgNPs when synthesized and tested under strictly anaerobic conditions that preclude Ag(0) oxidation and Ag+ release. Furthermore, we demonstrate that the toxicity of various AgNPs (PEG- or PVP- coated, of three different sizes each) accurately follows the dose–response pattern of E. coli exposed to Ag+ (added as AgNO3). Surprisingly, E. coli survival was stimulated by relatively low (sublethal) concentration of all tested AgNPs and AgNO3 (at 3–8 μg/L Ag+, or 12–31% of the minimum lethal concentration (MLC)), suggesting a hormetic response that would be counterproductive t...
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"Sulfidation of silver nanoparticles..." refers methods in this paper
...Supernatant silver ion concentrations were measured using inductively coupled plasma−atomic emission spectrometry (ICP-AES; TJA IRIS Advantage/1000 Radial ICAP Spectrometer; detection limit, 10 ppb) after acid digestion with concentrated HNO3. Duplicates of each sample were measured, with ion concentrations normalized by initial particle concentrations. Organisms and Media. Four model organisms were selected for this study: two species of fish, Danio rerio (zebrafish) and Fundulus heteroclitus (killifish); the nematode worm Caenorhabditis elegans; and the aquatic plant Lemna minuta (least duckweed). These organisms were selected to provide a diverse set of organisms and uptake pathways for AgNPs and Ag ions. Six common exposure media and DI water were used. All media were prepared using high purity chemicals and deionized water, with the exception of the salt blend, Instant Ocean (IO, Foster & Smith, Rhinelander, WI, U.S.A.), which was diluted to 10 parts per 1000 (10 ‰ on a mass per mass basis) with deionized water. Table 1 lists the organisms and six exposure media types used, and compares their chloride concentration, ionic strength, pH, and conductivity. The exact composition of 10 ‰ IO was estimated from an elemental composition analysis performed by ICP-AES.(51) Artificial seawater (ASW) was prepared according to Kester et al. (1967).(52) Toxicology....
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