Could Iron-Nitrogen Doping Modulate the Cytotoxicity of TiO₂ Nanoparticles?

Titanium dioxide nanoparticles (TiO₂ NPs) are found in several products on the market that include paints, smart textiles, cosmetics and food products. Besides these, TiO₂ NPs are intensively researched for their use in biomedicine, agriculture or installations to produce energy. Taking into account that several risks have been associated with the use of TiO₂ NPs, our aim was to provide TiO₂ NPs with improved qualities and lower toxicity to humans and the environment. Pure TiO₂ P25 NPs and the same NPs co-doped with iron (1%) and nitrogen atoms (P25-Fe(1%)-N NPs) by hydrothermal treatment to increase the photocatalytic activity in the visible light spectrum were in vitro evaluated in the presence of human lung cells. After 24 and 72 h of incubation, the oxidative stress was initiated in a time- and dose-dependent manner with major differences between pure P25 and P25-Fe(1%)-N NPs as revealed by malondialdehyde and reactive oxygen species levels. Additionally, a lower dynamic of autophagic vacuoles formation was observed in cells exposed to Fe-N-doped P25 NPs compared to the pure ones. Therefore, our results suggest that Fe-N doping of TiO₂ NPs can represent a valuable alternative to the conventional P25 Degussa particles in industrial and medical applications.