Excreted metabolite nanocoronas impact metabolic and toxicity responses of daphnids to silver nanoink

The rapid advancements of the modern world led to the creation of new materials and products at an unprecedented rate. Among these, nanoparticles have found extensive applications and frequently enter freshwater ecosystems. Daphnia magna is a widely used bioindicator species for the assessment of aquatic pollution. This study explores the impact of excreted metabolites on the toxicity mechanisms of silver nanoparticle ink using D. magna metabolite conditioned media. Two different life stages of daphnids were used to condition aqueous media and form metabolite-based nanocoronas with different compositions. The primary objective was to examine how these metabolite nanocoronas affect the observed impact of exposure on several physiological markers in daphnids including mortality, key enzyme activities and core metabolism. Conditioned media was also characterised to compare similarities in composition to assess the impact of silver nanoink. The response profiles to acute exposure varied among the tested media groups, with unfunctionalized nanoparticles exerting noticeably different responses on the investigated markers of physiology. Lethality was significantly reduced by the presence of excreted metabolites compared to unconditioned exposure to the silver nanoink, while the presence of metabolites had a more significant effect on key enzyme activities and metabolism of daphnids.