Silver nanowires kinetics and real-time imaging of in situ Ag ion dissolution in Daphnia magna

Abstract

Silver nanowires (AgNWs) as high-aspect-ratio nanomaterials are extensively employed in industrial products, and may pose potential risks of exposure to humans and other living organisms. Nevertheless, little is known about their potential environmental fates and toxicological characteristic. Herein, the uptake and depuration kinetics of AgNWs in Daphnia magna at various exposure concentrations were comprehensively evaluated for the first time. Further, the distribution pattern of released Ag+ in the gut of D. magna as well as the total amount of Ag+ were qualitatively and quantitatively investigated. Rapid accumulation of AgNWs in D. magna was observed, and the steady-state concentration was obtained within 24-h. Depuration of AgNWs was limited, with 30–40% of accumulated AgNWs being eliminated within 24-h. The released Ag+ from AgNWs in D. magna was monitored by real-time in situ imaging with the application of aggregation-induced emission luminogen. At equilibrium state of depuration, the released Ag+ reached 26.9 μg/g, equivalent to 5.4% of the total accumulated AgNWs in D. magna exposed to 500 μg/L AgNWs for 12-h. Such in vivo dissolution of AgNWs was significantly higher than that in D. magna culture medium in vitro (2.6%). Compared with other Ag nanoparticles, Ag+ release from AgNWs in D. magna contributed much less to the observed AgNWs toxicity, and was able to transport to inner sides of daphnids, including gills and hemolymph. The slow depurations of both AgNWs and Ag+ in D. magna may thus contribute to their joined chronic toxic effects.