Sulfidation of silver nanoparticle reduces its toxicity in zebrafish.

Chemical transformations of metal nanoparticles can be an important way to mitigate nanoparticle toxicity. Sulfidation of silver nanoparticle (AgNPs) is a natural process shown to occur in environment. Very few studies, employing microbes and embryonic stages of zebrafish, have shown reduction in AgNPs toxicity as a direct result of sulfidation. However the feasibility of reducing nanoparticle toxicity by sulfidation of AgNPs has never been studied in adult vertebrates. In this study, we have used adult zebrafish as a model to study the efficacy of sulfidation of AgNPs in reducing nanoparticle toxicity by employing a battery of biomarkers in liver and brain. While AgNPs enhanced liver oxidative stress, altered detoxification enzymes and affected brain acetylcholinesterase activity, sulfidation of AgNPs resulted in significant alleviation of changes in these parameters. Histopathological analyses of liver and sulphydryl levels also support the significance of sulfidated AgNPs in controlling the toxicity of AgNPs. Our study provides the first biochemical data on the importance of sulfidation of AgNPs in reducing biological toxicity in adult vertebrates.