In vitro evaluation of cytotoxicity of engineered metal oxide nanoparticles

The recent advances in nanotechnology and the corresponding popular usage of nanomaterials have resulted in uncertainties regarding their environmental impacts. In this study, we used a systematic approach to study and compare the in vitro cytotoxicity of selected engineered metal oxide nanoparticles to the test organisms — E. coli. Among the seven test nano-sized metal oxides, ZnO, CuO, Al₂O_3, La₂O_3, Fe₂O_3, SnO₂ and TiO_2, ZnO showed the lowest LD₅₀ of 21.1 mg/L and TiO₂ had the highest LD₅₀ of 1104.8 mg/L. Data of ¹⁴C-glucose mineralization test paralleled the results of bacteria viability test. After regression calculation, the cytotoxicity was found to be correlated with cation charges (R² = 0.9785). The higher the cation charge is, the lower the cytotoxicity of the nano-sized metal oxide becomes. To the best of our knowledge, this finding is the first report in nanotoxicology.