Titanium dioxide is typically micronized and coated for use in cosmetics products. The micronizing makes this somewhat heavy-feeling ingredient easier to spread on skin, plus a bit more cosmetically elegant. Micronized titanium dioxide is much more stable and can provide better sun protection than non-micronized titanium dioxide.

The vitaminC@P25TiO₂NPs, on the other side, did not have any effect on cell protection against ROS. This might be due to the fact that vitamin C, a well-known scavenger of ROS, could behave as prooxidant and even promote ROS and lipid peroxidation [39]. It was recently described that at small concentrations of vitamin C, the prooxidant effects dominate; while in large concentrations the antioxidant ones predominate [40]. The effect also depends on the cell state and the interaction of vitamin C with light. In this case, ascorbic acid may act as an antenna to harvest visible light when conjugated to P25TiO₂NPs. Indeed, it was previously found that this combination (in some ratios) could have an improved photocatalytic activity, possibly due to a red shift in its light absorbance [41]. Further studies on vitaminC@P25TiO₂NPs were not conducted, because of the poor antioxidant capacity [42].

Titanium dioxide nanoparticles are commonly found in a wide-range of consumer goods, including cosmetics, sunscreens, paints and colorings, ceramics, glass, textiles, construction materials, medicine, food, food packaging, and more. In Europe, cosmetic companies are required to label products that contain nanoparticles. In the U.S., companies are not.