Biological Response of Silver Nanoparticles Covered With <scp> <i>Ilex paraguariensis</i> </scp> Extract or Polyvinylpyrrolidone: A Nanotoxicological Study

The development of nanomaterials and the search for alternatives that reduce adverse effects have become a central focus in the scientific community. However, this progress has not been accompanied by exhaustive nanotoxicological studies, often leading to the assumption that the addition of natural or inert components minimizes the harmful effects of nanostructures. Silver nanoparticles (AgNPs), widely used for their antimicrobial properties, are known to be cytotoxic and potentially harmful to the environment and human health. To mitigate these risks, in this study core-shell nanoparticles were synthesized using coatings of either natural ilex paraguariensis (yerba mate [YM]) extract or synthetic polyvinylpyrrolidone (PVP) to evaluate whether additives confer a safer alternative. Both formulations were fully characterized for dynamic light scattering, zeta potential, and spectroscopy UV-visible. Then, these formulations were evaluated for cytotoxicity in vitro using human skin and liver cell lines and assessed in vivo using the zebrafish model to determine general and organ-specific toxicity. Results showed that AgNPs-YM induced toxicity across all tested concentrations in both in vitro and in vivo systems, with the highest concentration causing mortality, organ damage, and increased production of reactive oxygen species (ROS). In contrast, AgNPs-PVP exhibited significantly lower toxicity under the same conditions. These findings demonstrate that natural-origin coatings do not guarantee safety, and highlight the need for the implementation of exhaustive toxicological screening prior to the validation of new nanomaterials.