Genotoxicity evaluation of titanium dioxide nanoparticles using the Ames test and Comet assay

ABSTRACT Titanium dioxide nanoparticles (TiO 2 ‐NPs) are being used increasingly for various industrial and consumer products, including cosmetics and sunscreens because of their photoactive properties. Therefore, the toxicity of TiO 2 ‐NPs needs to be thoroughly understood. In the present study, the genotoxicity of 10nm uncoated sphere TiO 2 ‐NPs with an anatase crystalline structure, which has been well characterized in a previous study, was assessed using the Salmonella reverse mutation assay (Ames test) and the single‐cell gel electrophoresis (Comet) assay. For the Ames test, Salmonella strains TA102, TA100, TA1537, TA98 and TA1535 were preincubated with eight different concentrations of the TiO 2 ‐NPs for 4 h at 37 °C, ranging from 0 to 4915.2 µg per plate. No mutation induction was found. Analyses with transmission electron microscopy (TEM) and energy‐dispersive X‐ray spectroscopy (EDS) showed that the TiO 2 ‐NPs were not able to enter the bacterial cell. For the Comet assay, TK6 cells were treated with 0–200 µg ml –1 TiO 2 ‐NPs for 24 h at 37 °C to detect DNA damage. Although the TK6 cells did take up TiO 2 ‐NPs, no significant induction of DNA breakage or oxidative DNA damage was observed in the treated cells using the standard alkaline Comet assay and the endonuclease III ( Endo III) and human 8‐hydroxyguanine DNA‐glycosylase (hOGG1)‐modified Comet assay, respectively. These results suggest that TiO 2 ‐NPs are not genotoxic under the conditions of the Ames test and Comet assay. Published 2012. This article is a US Government work and is in the public domain in the USA.