Characterizing the behavior, uptake, and toxicity of NM300K silver nanoparticles in Caenorhabditis elegans

Using Caenorhabditis elegans as a model organism, this study addresses the potential linkage between toxicity of NM300K Ag nanoparticles (AgNPs), their particle size distribution and the presence of dissolved Ag in the test media. Of the three endpoints assessed (growth, fertility and reproduction), reproduction was the most sensitive, with 50% effect concentration (EC50) ranging from 0.26-0.84 mg Ag L-1 and 0.08-0.11 mg Ag L-1 for NM300K and AgNO3, respectively. Silver uptake by C. elegans was similar for both forms of Ag, while bioaccumulation was higher in AgNO3 exposure. The observed differences in toxicity between NM300K and AgNO3 did not correlate to bioaccumulated Ag, which suggests the toxicity to be a function of the type of exposing agent (AgNPs vs AgNO3) and their mode of action. Before addition of the food source, E. coli, size fractionation revealed that dissolved Ag comprised 13-90 % and 4-8 % of total Ag in the AgNO3 and NM300K treatments, respectively. No dissolved Ag was detectable in the actual test media, due to immediate Ag adsorption to bacteria. Results from the current study highlight that information on behavior and characterization of exposure conditions is essential for nanotoxicity studies.