Cellular toxicity of TiO2 nanoparticles in anatase and rutile crystal phase.

Titanium dioxide nanoparticles are massively produced and widely used in daily life, which has posed potential risk to human health. However, the molecular mechanism of TiO(2) nanoparticles (NPs) with different crystal phases is not clear. In this study, the characterization of two crystalline phases of TiO(2) NPs is evaluated by transmission electron microscopy and X-ray absorption fine structure spectrum; an interaction of these TiO(2) NPs with HaCaT cells is studied in vitro using transmission electron microscopy, chemical precipitation method, and X-ray absorption fine structure spectrometry. The coordination and surface properties indicate that only the anatase-TiO(2) NPs allow spontaneous reactive oxygen species (ROS) generation, but rutile-TiO(2) NPs do not after dispersion. The interaction between TiO(2) NPs and cellular components might also generate ROS for both anatase-TiO(2) NPs and rutile-TiO(2) NPs. The ROS generation could lead to cellular toxicity if the level of ROS production overwhelms the antioxidant defense of the cell or induces the mitochondrial apoptotic mechanisms. Furthermore, Ti had a direct combination with some protein or DNA after NPs enter the cell, which could also lead to cellular toxicity.