Extracellular polymeric substances reprogram the environmental behavior and impact of silver nanoparticles on...

Engineered nanoparticles, and silver nanoparticles (nAg) among them, can be released into aquatic environments, where interactions with natural biomolecules can significantly alter their environmental behaviour and toxicity. Recognizing the growing need to integrate ecocorona processes into nanoparticle risk assessment, this study investigates extracellular polymeric substances (EPS) from green alga Chlamydomonas reinhardtii as key environmental modulators of nAg transformations and biological effects. The behaviour of citrate-coated (Cit-nAg) and lipoic acid-coated (Lip-nAg) nanoparticles in the presence and absence of environmentally relevant concentrations of algal EPS was evaluated through combined physicochemical characterization and ecotoxicological assays to assess EPS-driven changes in aggregation dynamics, dissolution behaviour, and toxicity toward freshwater phytoplankton. EPS adsorption markedly reshaped nAg behaviour in a coating-dependent manner: while EPS enhanced colloidal stability for both materials, it reduced Ag⁺ release and toxicity for Cit-nAg, but promoted dissolution and amplified biological effects for Lip-nAg, showing the potential dual role of phytoplankton EPS in shaping nAg identity in freshwater. These results reveal that EPS-driven ecocorona formation can either mitigate or enhance nAg toxicity depending on the underlying surface chemistry. By demonstrating how environmentally derived biomolecules regulate the coupling between nanoparticle transformations and toxicological responses, this study supports the critical role of ecocorona formation as a central component in environmentally realistic assessments of nanomaterial fate and risk.