Inhibition of the ROS-mediated cytotoxicity and genotoxicity of nano-TiO2 toward human keratinocyte cells by iron doping

Nano-TiO2 powders are widely used in sunscreen lotions as UV filters in combination with other substances. The activation of TiO2 by UV rays leads to the release of reactive oxygen species (ROS, e.g., hydroxyl radicals and singlet oxygen) which are potentially harmful. For this reason the TiO2 particles are generally coated with inert materials (e.g., silica or alumina) that inhibit such reactivity. Alternatively, the release of ROS may be inhibited by introducing in the TiO2 lattice doping elements. In the present study we report a new modification consisting in a wet impregnation of TiO2 with iron salts followed by a thermal treatment that results in an inhibition of the surface reactivity. The insertion of iron ions also gradually reduces the ability of photo-activated TiO2 to cleave DNA and proteins. At the same time, a clear inhibition of cyto- and geno-toxicity toward human (HaCaT) keratinocytes was observed. The data presented herein suggest the insertion of Fe3+ ions at the surface of nano-TiO2 as a promising strategy to reduce the photo-induced toxicity of nano-TiO2 powders.