Silver nanoparticle-specific mitotoxicity inDaphnia magna

Abstract

Silver nanoparticles (Ag NPs) are gaining popularity as bactericidal agents in commercial products; however, the mechanisms of toxicity (MOT) of Ag NPs to other organisms are not fully understood. It is the goal of this research to determine differences in MOT induced by ionic Ag(+) and Ag NPs in Daphnia magna, by incorporating a battery of traditional and novel methods. Daphnia embryos were exposed to sublethal concentrations of AgNO3 and Ag NPs (130-650 ng/L), with uptake of the latter confirmed by confocal reflectance microscopy. Mitochondrial function was non-invasively monitored by measuring proton flux using self-referencing microsensors. Proton flux measurements revealed that while both forms of silver significantly affected proton efflux, the change induced by Ag NPs was greater than that of Ag(+). This could be correlated with the effects of Ag NPs on mitochondrial dysfunction, as determined by confocal fluorescence microscopy and JC-1, an indicator of mitochondrial permeability. However, Ag(+) was more efficient than Ag NPs at displacing Na(+) within embryonic Daphnia, based on inductively coupled plasma-mass spectroscopy (ICP-MS) analysis. The abnormalities in mitochondrial activity for Ag NP-exposed organisms suggest a nanoparticle-specific MOT, distinct from that induced by Ag ions. We propose that the MOT of each form of silver are complementary, and can act in synergy to produce a greater toxic response overall.

Response of biochemical biomarkers in the aquatic crustacean Daphnia magna exposed to silver nanoparticles

“…These changes could be attributed to increased mitochondrial damage by AgNPs. Sublethal treatment with Ag + did not show an identical response which is consistent with Stensberg et al (2014) who observed different mechanisms of toxicity for Ag + and AgNPs in D. magna. As Ag + may dissolve from AgNPs, these two types of Ag act complimentary and could produce a greater toxic response together.…”

“…Several studies reported that AgNPs induced toxicity, uptake, and accumulation in D. magna (Bondarenko et al 2013;Gaiser et al 2011;Stensberg et al 2014;Asghari et al 2012;Hoheisel et al 2012;Zou et al 2014). In this study, the immobilization and subsequent mortality of D. magna was dependent on exposure concentrations and time.…”

“…The AgNP and Ag + exposure concentrations were prepared in the range 0.1-25 and 0.01-25 μg Ag/L, respectively, by diluting the AgNP and AgNO 3 stock suspensions, respectively, in SCM immediately prior to use in the experiments. These concentrations were selected on the basis of previously published studies on toxicity effects of AgNPs on D. magna (Bondarenko et al 2013;Gaiser et al 2011;Stensberg et al 2014;Asghari et al 2012;Hoheisel et al 2012;Zou et al 2014). The AgNPs stock suspension was prepared by diluting purified synthesized AgNPs in sterile UPW at the final concentration of 25 mg Ag/L.…”

Assessment of silver nanoparticle toxicity for common carp (Cyprinus carpio) fish embryos using a novel method controlling the agglomeration in the aquatic media

“…In contrast, toxicities of NPs of other metals compared in the same study (CuO, ZnO) were primarily caused by the dissolved fractions exclusively (Seo et al 2014). Correspondingly, (Stensberg et al 2014) revealed that silver nanoparticles had greater impacts on mitochondrial functions in D. magna (in comparison with the effects of dissolved Ag + ), which could mechanistically explain the observed higher toxicities of Ag nanoparticles.…”

Sunlight-driven reduction of silver ion to silver nanoparticle by organic matter mitigates the acute toxicity of silver to Daphnia magna

“…Truncated triangular silver nanoplates with a lattice plane as the basal plane displayed stronger biocidal action to gram-negative bacterium Escherichia coli than Ag + (Pal et al, 2007). Sublethal concentrations of Ag + and AgNPs exposure to Daphnia embryos also revealed that there is an AgNP-specific mitotoxicity to Daphnia magna (Stensberg et al, 2014). AgNP-exposed common grass, Lolium multiflorum, failed to develop root hairs, had highly vacuolated and collapsed cortical cells, which was not observed for Ag + -exposed group (Yin et al, 2011).…”