Effects of coating materials and size of titanium dioxide particles on their cytotoxicity and penetration into the cellular membrane

Abstract

In order to estimate the effects of the size and surface treatment (coating or non-coating) of titanium dioxide particles on their cytotoxicity and penetration into the cellular membrane, two types of non-treated titanium dioxide (TiO₂)  particles of 20 nm (LU175) and 250 nm (LU205) were exposed to CHO cells, RBL-2H3 cells, A431 cells, B16 melanoma, NHEK(F), and NHSF, and six types of surface-treated or non-treated TiO₂ particles of 35 nm were exposed to RBL-2H3 cells and NHSF. The order of half-maximal inhibitory concentrations (IC50s) of LU175 was NHSF < CHO, RBL-2H3 < A431 < B16 melanoma, NHEK(F). On the other hand, LU205 showed no cytotoxicity against any cells. Surface-treated TiO₂ showed much less cytotoxicity against RBL-2H3 cells than non-treated TiO₂. Then, between 0.5 and 10 mg of LU175 or LU205 was exposed to CHO cells. After 24 hr, the amount of LU175 in cellular cytosol increased dose-dependently. On the other hand, the amount of LU205 in cellular cytosol was much less than that of LU175. The proportion of surface-treated TiO₂ in the cellular cytosol of RBL-2H3 cells differed for each coating material. These results suggested that TiO₂ has different cytotoxicities among cell lines, and that of surface-treated TiO₂ was weaker than that of non-treated TiO₂. TiO₂ located in cytosol might be the main cause of cytotoxicity.