Biotic and Abiotic Interactions in Aquatic Microcosms Determine Fate and Toxicity of Ag Nanoparticles: Part 2–Toxicity and Ag Speciation

Abstract

To study the effects of complex environmental media on silver nanoparticle (AgNP) toxicity, AgNPs were added to microcosms with freshwater sediments and two species of aquatic plants (Potamogeton diversifolius and Egeria densa), followed by toxicity testing with microcosm surface water. Microcosms were designed with four environmental matrices in order to determine the contribution of each environmental compartment to changes in toxicity: water only (W), water + sediment (WS), water + plants (WP), and water + plants + sediment (WPS). Silver treatments included AgNPs with two different coatings, gum arabic (GA-AgNPs) or polyvinylpyrollidone (PVP-AgNPs), as well as AgNO(3). Water samples taken from the microcosms at 24 h postdosing were used in acute toxicity tests with two standard model organisms, early life stage zebrafish (Danio rerio) and Daphnia magna. Speciation of Ag in these samples was analyzed using Ag L3-edge X-ray absorption near edge spectroscopy (XANES). Silver speciation patterns for the nanoparticle treatments varied significantly by coating type. While PVP-AgNPs were quite stable and resisted transformation across all matrices (>92.4% Ag(0)), GA-AgNP speciation patterns suggest significantly higher transformation rates, especially in treatments with plants (<69.2% and <58.8% Ag(0) in WP and WPS, respectively) and moderately increased transformation with sediments (<85.6% Ag(0)). Additionally, the presence of plants in the microcosms (with and without sediments) reduced both the concentration of Ag in the water column and toxicity for all Ag treatments. Reductions in toxicity may have been related to decreased water column concentrations as well as changes in the surface chemistry of the particles induced by organic substances released from the plants.

Perturbation of cellular mechanistic system by silver nanoparticle toxicity: Cytotoxic, genotoxic and epigenetic potentials

“…In the recent past few more realistic approaches to study transformation were explored as microcosm and mesocosm approaches. They can be applied to further widen the understanding of the possible transformation of Ag NPs in environmental media and thus the probable toxicity in in vivo model systems [213,214].…”

Detection, characterization and quantification of inorganic engineered nanomaterials: A review of techniques and methodological approaches for the analysis of complex samples

“…SP-ICP-MS has also been applied to study the fate of silver nanoparticles in in vitro human digestion [104], lake mesocosms [50] and washing solutions from commercial detergents [90], to track their dissolution [127] and agglomeration [128] in natural waters or their release from food additives [129]. [142,143] and ZnO and CuO [144], and for speciation of silver in waters and soils from microcosm [145] and mesocosms [146] experiments.…”

Characterization of Nanomaterials for NanoEHS Studies

“…AF4-ICP-MS is especially powerful in this aspect as it provides a wealth of information about each particle size in a heterogeneous mixture (Hoque et al, 2012;Gray et al, 2012). It has even been used to elucidate transformations of silver nanoparticles in environmental studies (Unrine et al, 2012;Bone et al, 2012) and has recently enabled the measurement of metallic clusters as small as 1 nm (Pettibone et al, 2013). Separation of particles by shape is also possible (Pettibone et al, 2013;Gigault et al, 2010), which is important since particle shape has been suggested to play a role in toxicological response (Schaeublin et al, 2012).…”