Hazard and environmental behavior of encapsulated mycogenic silver nanoparticles in aquatic environments

Silver nanoparticles (AgNPs) synthesized from Aspergillus niger IBCLP20 exhibit strong antimicrobial properties; however, strategies to mitigate their environmental risks remain insufficiently validated across contrasting aquatic systems. Here, we assessed calcium alginate encapsulation (AgNPs IBCLP20/CA ) as a safe-by-design approach, integrating silver release dynamics with short-term ecotoxicity in freshwater and marine species. In this context, safe-by-design refers to the use of calcium alginate microcapsules to modulate the release of dissolved silver from mycogenic AgNPs intended for water disinfection, thereby reducing and delaying peak exposure without altering the intrinsic toxicity of silver. Silver concentrations were quantified using ICP-MS and energy-dispersive X-ray fluorescence spectroscopy. Leachate-based assays revealed higher sensitivity in marine taxa, with Paracentrotus lividus (LOEC = 1%) and Daphnia magna (LOEC = 0.781%) were the most responsive species, while freshwater Danio rerio embryos and Raphidocelis subcapitata were unaffected. Silver release strongly depended on medium ionic strength, decreasing from 19.3 μg⋅L −1 in ultrapure water to 0.83 μg⋅L −1 in hard water. Hazard assessment yielded lower predicted no-effect concentration (PNEC) values for AgNPs IBCLP20/CA in freshwater than in seawater, indicating ecosystem-specific mitigation performance. These findings demonstrate that the ionic composition governs nanoencapsulation efficiency and that risk reduction strategies for biogenic AgNPs cannot be generalized across aquatic environments. Our results provide quantitative support for integrating encapsulation performance into environmental risk assessment frameworks for antimicrobial nanomaterials. Because the degradation of the alginate matrix may remobilize additional silver over time, encapsulation should be viewed as a hazard mitigation and exposure modulation strategy rather than a permanent elimination of silver-related risks.