Nanoparticles (NPs) with reactive oxygen species (ROS)-regulating ability have recently attracted great attention as promising agents for nanomedicine. In the present study, we have analyzed the effects of TiO2 defect structure related to the presence of stoichiometric (Ti4+) and non-stoichiometric (Ti3+ and Ti2+) titanium ions in the crystal lattice and TiO2 NPs aggregation ability on H2O2- and tBOOH-induced ROS production in L929 cells. Synthesized TiO2-A, TiO2-B, and TiO2-C NPs with varying Ti3+(Ti2+) content were characterized by XRD, TEM, SAXS, XPS, and optical spectroscopy methods. Given the role of ROS-mediated toxicity for metal oxide NPs, L929 cell viability and changes in the intracellular ROS levels in H2O2- and tBOOH-treated L929 cells incubated with TiO2 NPs have been evaluated. Our research shows that both the amount of non-stoichiometric Ti3+ and Ti2+ ions in the crystal lattice of TiO2 NPs and NPs aggregative behavior affect their catalytic activity, in particular, H2O2 decomposition and, consequently, the efficiency of aggravating H2O2- and tBOOH-induced oxidative damage to L929 cells. TiO2-A NPs reveal the strongest H2O2 decomposition activity aligning with their less pronounced additional effects on H2O2-treated L929 cells due to the highest amount of Ti3+(Ti2+) ions. TiO2-C NPs with smaller amounts of Ti3+ ions and a tendency to aggregate in water solutions show lower antioxidant activity and, consequently, some elevation of the level of ROS in H2O2/tBOOH-treated L929 cells. Our findings suggest that synthesized TiO2 NPs capable of enhancing ROS generation at concentrations non-toxic for normal cells, which should be further investigated to assess their possible application in nanomedicine as ROS-regulating pharmaceutical agents.
