Comparative analysis of nanosilver toxicity in C. elegans: influence of exposure media on accumulation, physiological and biochemical effects

Caenorhabditis elegans is widely used in nanotoxicology studies involving silver nanoparticles (AgNP). However, variations in test media composition can influence AgNP toxicity in worms, complicating cross-study comparisons. This study evaluated the effects of six commonly used media: M9 buffer, K-medium, S-basal, EPA water, Nematode Growth Medium agar (NGM), and "Biofilm" (a combination of NGM and EPA water) on biological responses in worms without the presence of AgNP and the toxicity and accumulation of citrate-coated AgNP (cit-AgNP). Our results indicate that, in the absence of AgNP, NGM and Biofilm were the least disruptive to worm size and DAF-16 translocation (p < 0.05), suggesting lower systemic stress responses. In contrast, all liquid media significantly affected at least one of these parameters. In the presence of cit-AgNP, toxicity patterns in C. elegans at 5 mg/L (administered in 1 mL of food source) varied across the tested media (EPA water, NGM, and Biofilm). Worms in EPA water exhibited the most pronounced effects on size, brood size, and GSH/GSSG levels, whereas those in NGM agar were unaffected. These differences are attributed to the media's impact on worms, observed for EPA water, and reduced Ag accumulation in worms due to increased Ag migration to agar, particularly in NGM. This study demonstrates that the treatment scenarios currently used for assessing AgNP toxicity in C. elegans produce varying outcomes due to the media's intrinsic effects on worms and differences in Ag accumulation. Our findings underscore the need for standardized media to ensure accurate and comparable toxicity assessments.