TiO2 NPs appeared to be more toxic to nematode Caenorhabditis elegans than submicron-sized TiO2. At a concentration of 1 mg/l, 7 nm particles affected its fertility and survival rate and were more toxic than 20 nm anatase particles. Similarly, Hu et al. showed that rutile particles (10–20 nm), at concentrations above 1 g/kg soil, can be bio-accumulated in earthworms, where they induce oxidative stress, inhibit the activity of cellulase and induce DNA and mitochondrial damage.
In order to contribute with experimental evidence that could help to achieve a better understanding of the field for future regulation, in the present work, the biocompatibility of commercial P25TiO2NPs (one type of TiO2NPs used in sunscreen formulations) and two novel functionalized P25TiO2NPs were evaluated under solar simulated irradiation. White light, generated by red, blue, and yellow LEDs, together with UV ones, was chosen to simulate the solar spectra. Functionalization of TiO2NPs was made with antioxidant vitamins in order to prevent the expected photo-initiated ROS production when nanoparticles are exposed to the simulated solar spectra. Vitamin B2 (riboflavin) and vitamin C were chosen to carry out the functionalization because they are water-soluble, low-cost, and are a constitutive part of biological processes. In addition, it is known that both have the potential to prevent macromolecular oxidation by ROS [23], [24], [25], [26].