Assessing the Cytotoxicity of TiO Nanoparticles with a Different Ti(Ti)/Ti Ratio.

Titanium dioxide (TiO) nanoparticles are promising biomedical agents characterized by good biocompatibility. In this study, we explored the cytotoxicity of TiO nanoparticles with a different Ti(Ti)/Ti ratio and analyzed the efficiency of eryptosis indices as a tool in nanotoxicology. Two types of TiO nanoparticles (NPs) were synthesized by the hydrolysis of titanium alkoxide varying the nitric acid content in the hydrolysis mixture. Transmission electron microscopy (TEM) images show that 1-TiO and 2-TiO NPs are 5 nm in size, whereas X-ray photoelectron spectroscopy (XPS) reveals different Ti (Ti)/Ti ratios in the crystal lattices of synthesized NPs. 1-TiO nanoparticles contained 54% Ti, 38% Ti, and 8% Ti, while the relative amount of Ti and Ti in the crystal lattice of 2-TiO nanoparticles was 63% and 37%, respectively. Cell viability and cell motility induced by TiO nanoparticles were investigated on primary fibroblast cultures. Eryptosis modulation by the nanoparticles along with cell death mechanisms was studied on rat erythrocytes. We report that both TiO nanoparticles do not decrease the viability of fibroblasts simultaneously stimulating cell migration. Data from in vitro studies on erythrocytes indicate that TiO nanoparticles trigger eryptosis via ROS- (1-TiO) and Ca-mediated mechanisms (both TiO nanoparticles) suggesting that evaluation of eryptosis parameters is a more sensitive nanotoxicological approach for TiO nanoparticles than cultured fibroblast assays. TiO nanoparticles are characterized by low toxicity against fibroblasts, but they induce eryptosis, which is shown to be a promising tool for nanotoxicity screening. The Ti (Ti)/Ti ratio at least partly determines the cytotoxicity mechanisms for TiO nanoparticles.