Differential Cytotoxicity of Metallic Oxide Nanoparticles in Mammalian Cells

Because the putative cytotoxic effects of metal oxide nanoparticles on human cell types have not been fully elucidated, we investigated the hypothesis that titanium oxide, magnesium oxide, and zinc oxide nanoparticles exert differential cytotoxic effects on human astrocytoma (U87) cells and human fibroblasts (HFF-1 cells). Treatment with 5 mu g/mL of titanium oxide (but not magnesium or zinc oxide) nanoparticles induced significant decreases in survival of U87 but not that of HFF-1 cells. However, treatment with zinc oxide nanoparticles at higher concentrations exerted greater decreases in survival of U87 cells more so than in HFF-1 cells, compared to the corresponding effects of titanium and magnesium oxide nanoparticles. By contrast, treatment of both cell types with magnesium oxide nanoparticles did not lower cell survival below 50% even at higher concentrations. Thus, these results are consistent with our hypothesis and may have implications in health risks involved with exposure to metal oxide nanoparticles.