Exposure, Cytotoxicity and Cellular Uptake of Silver (Ag) and Gold (Au) Nanoparticles in Human Bronchial Epithelial Cells During Nanoparticle Synthesis

Abstract

Silver (Ag) and gold (Au) nanoparticles (NPs) are widely used in biomedicine, electronics, and catalysis, but their potential toxicity raises occupational health concerns. This study assessed the cytotoxicity and cellular interactions of Ag and Au NPs in human bronchial epithelial cells (BEAS-2B) using a standardized OECD three-tiered approach, alongside characterization of lung-deposited surface area (LDSA) concentrations during NP synthesis, which remained within ranges typically reported in occupational environments. Transmission electron microscopy revealed that AgNPs formed irregular clusters (~8.7 nm primary size, >30 nm aggregates), whereas AuNPs remained spherical (~13.4 nm). Real-time cytotoxicity analysis (xCELLigence) showed acute toxicity of AgNPs at 5 μg/cm2, while AuNPs exhibited no cytotoxic effects. Dark-field and 3D hyperspectral imaging demonstrated that some AgNPs were internalized by BEAS-2B cells, whereas AuNPs remained mostly on the cell surface, indicating that uptake alone does not determine cytotoxicity. The greater dissolution potential of AgNPs and possible release of Ag+ ions may contribute to the enhanced cytotoxic effects observed in comparison to AuNPs, as suggested in previous studies. Although oxidative stress, mitochondrial dysfunction, and related cellular mechanisms were not directly assessed in the present study, the findings demonstrate differential cellular responses following nanoparticle exposure under realistic occupational exposure conditions. These results contribute to understanding nanoparticle–cell interactions and support the need for further mechanistic investigations to inform safer nanomaterial use.