Genotoxic evaluation of titanium dioxide nanoparticles in vivo and in vitro

With the extensive application of titanium dioxide (TiO₂) nanoparticles (NPs) in food industry, there is a rising debate concerning the possible risk associated with exposure to TiO₂ NPs. The purpose of this study is to evaluate the genotoxicity of TiO₂ NPs using in vivo and in vitro test systems. In vivo study, the adult male Sprague-Dawley rats were exposed to anatase TiO₂ NPs (75 ± 15 nm) through intragastric administration at 0, 10, 50 and 200 mg/kg body weight every day for 30 days. The γ-H₂AX assay showed TiO₂ NPs could induce DNA double strand breaks in bone marrow cells after oral administration. However, the micronucleus test revealed that the oral-exposed TiO₂ NPs did not cause damage to chromosomes or mitotic apparatus observably in rat bone marrow cells. In vitro study, Chinese hamster lung fibroblasts (V79 cells) were exposed to TiO₂ NPs at the dose of 0, 5, 10, 20, 50 and 100 μg/mL. Significant decreases in cell viability were detected in all the treated groups after 24 h and 48 h exposure. Significant DNA damage was only observed at the concentration of 100 μg/mL after 24 h treatment using the comet assay. The obvious gene mutation was observed at the concentration of 20 and 100 μg/mL after 2 h treatment using hypoxanthine-guanine phosphoribosyl transferase (HPRT) gene mutation assay. This study presented a comprehensive genotoxic evaluation of TiO₂ NPs, and TiO₂ NPs were shown to be genotoxic both in vivo and in vitro tests. The gene mutation and DNA strand breaks seem to be more sensitive genetic endpoints for the detection of TiO₂ NPs induced genotoxic effects.