Surface coatings and eco-corona as modulators of silver nanoparticle toxicity in freshwater fish

The rapid progress of nanotechnology has inevitably led to the increasing presence of nanopollutants in aquatic environments. Silver nanoparticles (AgNP), or nanosilver, are among the most widely used nanomaterials owing to their unique biocidal properties; however, nanotoxicological concerns have risen in parallel with their expanding applications. Freshwater systems represent one of the most important final sinks for these contaminants, and fish are widely used test organisms for toxicological assessment due to their sensitivity, physiological complexity, and multiple exposure routes. This mini-review aimed to synthesize current knowledge on surface-driven AgNP toxicity in freshwater fish, focusing on the role of capping agents, eco-corona formation, and environmentally relevant transformations. A structured literature search across five databases was conducted following the reporting guidelines of the PRISMA extension for scoping reviews (PRISMA-ScR), retrieving 21 studies that met the inclusion criteria of waterborne exposure and at least one comparative ecotoxicological assessment of surface modulators. Evidence indicates that surface coating clearly influences toxicological outcomes; however, contradictions remain regarding whether toxicity is driven by the coating itself, the nanoparticle, or Ag⁺ release, with particle size and surface charge emerging as the most consistent physicochemical drivers. Humic and fulvic substances represent the most studied environmental modifiers and generally exert mitigating effects on AgNP toxicity, while also markedly influencing particle fate and bioavailability. Knowledge gaps persist regarding exposures at environmentally relevant concentrations, the ecotoxicity of green-synthesized AgNP in fish, and the underrepresentation of eco-corona studies relative to coating-focused research, reflecting the current state of the literature in this field.