OBJECTIVETo observe the effects of different sized titanium dioxide on reactive oxygen species (ROS) levels.

METHODSForty-eight healthy mice were divided into 3 groups randomly: control group (distilled water), 50 nm TiO₂ (5 g/kg) group and 120 nm TiO₂ (5 g/kg) group. The mice were exposed to distilled water or TiO₂ by a syringe via gastrointestinal tract in a minute. One week later, the mice were sacrificed and the liver, kidney and brain (cortex, hippocampus) were collected. The contents of Ti in the above tissues of mice were measured by ICP-MS. The ROS levels in the tissues were measured by flow cytometry.

RESULTSThere was no significant difference in organ coefficient between two exposure groups and control group (P > 0.05). The Ti contents in liver, kidney, cortex and hippocampus of two exposure groups were higher than those of control group (P < 0.05); The Ti contents of above four tissues in 50 nm TiO₂ group were higher than those in 120 nm group (P < 0.05). The ROS levels in liver, kidney and cortex cells of two exposure groups (273.2 ± 32.5, 160.2 ± 28.5, 74.9 ± 8.9; 159.4 ± 15.9, 64.4 ± 7.5, 41.2 ± 5.6) significantly increased, as compared with control group (74.9 ± 6.4, 24.9 ± 2.8, 32.8 ± 3.1) (P < 0.05). The ROS levels in hippocampus cells in 50 nm TiO₂ group were significantly higher than those in control group (P < 0.05). The ROS levels of above four tissues in 50 nm group were significantly higher than those in 120 nm TiO₂ group (P < 0.05).

CONCLUSIONAfter mice were exposed to 50 nm and 120 nm TiO₂ particles via gastrointestinal tract, Ti could be distributed into the liver, kidney and the brain tissues in mice, resulting in the enhanced ROS levels in liver, kidney, cortex and hippocampus cells. Moreover, the ROS levels induced by 50 nm TiO₂ particles are significantly higher than those induced by 120 nm TiO₂ particles.