Genotoxic effects of zinc oxide and titanium dioxide nanoparticles on root meristem cells of Allium cepa by comet assay

Nanogenotoxicity is an emergent field, relevant for estimating the potential genotoxic risk of nanomaterials. In this study we investigated the genotoxic potential of zinc oxide (ZnO, <35 and 50 nm) and titanium dioxide (TiO2, 21 and 50 nm) nanoparticles (NPs) in the nuclei of Allium cepa root meristem cells by using a modified alkaline comet assay. ZnO and TiO2 NPs were supplied to cells treated in vitro at 3 different concentrations (10, 100, and 1000 mu g/mL). For the comet assay, our results indicate a dose-dependent increment in DNA damage in cells exposed to 100 and 1000 mu g/mL of ZnO NPs (<= 35 and 50 nm) for percentage of DNA tail (%DNA tail). On the other hand, the results from TiO2 NPs indicated that the DNA damage in the cells exposed to only the highest concentration (1000 mu g/mL) of TiO2 NPs (21 nm) is statistically significant in comparison to the control cells, while all concentrations of TiO2 NPs (50 nm) are stat