Zinc oxide nanoparticles-induced DNA damage in human lymphocytes

Abstract

Zinc oxide (ZnO) nanoparticles (<20 nm) were synthesised by sol-gel method and characterised by X-ray diffraction (XRD). Extensive use of ZnO in sunscreens and cosmetics, and their reported photoclastogenicity has prompted us to investigate its genotoxic potential. We have assessed the ZnO-induced DNA damage, intracellular ROS generation and change in mitochondrial membrane potential (ΔΨm), employing alkaline single cell gel electrophoresis (comet assay), flow cytometry and spectrofluorometric analysis. Significant increase in the Olive tail moment (OTM-62.72) in treated lymphocytes vis-a-vis untreated control (OTM-0.78), clearly indicated the formation of ZnO nanoparticles-induced single strand breaks. Exposure of human lymphocytes to ZnO nanoparticles also resulted in significant reduction in membrane potential (ΔΨm). Enhancement in fluorescence intensity of intracellular probe 2′,7′-dichlorofluorescein (DCF), in treated cells suggested the ZnO-induced oxidative stress. Overall, the data revealed the genotoxic potential of ZnO nanoparticles and their ability to perturb the mitochondrial membrane potential, possibly through oxidative mechanism.