Genotoxicity of polyvinylpyrrolidone-coated silver nanoparticles in BEAS 2B cells

Abstract

Silver nanoparticles (AgNPs) are widely utilized in various consumer products and medical devices, especially due to their antimicrobial properties. However, several studies have associated these particles with toxic effects, such as inflammation and oxidative stress in vivo and cytotoxic and genotoxic effects in vitro. Here, we assessed the genotoxic effects of AgNPs coated with polyvinylpyrrolidone (PVP) (average diameter 42.5±14.5nm) on human bronchial epithelial BEAS 2B cells in vitro. AgNPs were dispersed in bronchial epithelial growth medium (BEGM) with 0.6mg/ml bovine serum albumin (BSA). The AgNP were partially well-dispersed in the medium and only limited amounts (ca. 0.02μgAg+ ion/l) could be dissolved after 24h. The zeta-potential of the AgNPs was found to be highly negative in pure water but was at least partially neutralized in BEGM with 0.6mg BSA/ml. Cytotoxicity was measured by cell number count utilizing Trypan Blue exclusion and by an ATP-based luminescence cell viability assay. Genotoxicity was assessed by the alkaline single cell gel electrophoresis (comet) assay, the cytokinesis-block micronucleus (MN) assay, and the chromosomal aberration (CA) assay. The cells were exposed to various doses (0.5–48μg/cm2 corresponding to 2.5–240μg/ml) of AgNPs for 4 and 24h in the comet assay, for 48h in the MN assay, and for 24 and 48h in the CA assay. DNA damage measured by the percent of DNA in comet tail was induced in a dose-dependent manner after both the 4-h and the 24-h exposures to AgNPs, with a statistically significant increase starting at 16μg/cm2 (corresponding to 60.8μg/ml) and doubling of the percentage of DNA in tail at 48μg/cm2. However, no induction of MN or CAs was observed at any of the doses or time points. The lack of induction of chromosome damage by the PVP-coated AgNPs is possibly due to the coating which may protect the cells from direct interaction with the AgNPs, either by reducing ion leaching from the particles or by causing extensive agglomeration of the nanoparticles, with a possible reduction of the cellular uptake.