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].

It is a national high-tech enterprise, a national top 500 chemical enterprise, and the largest titanium dioxide exporter in China. The main products are TiO2, zirconium products, sulfuric acid and sulfate. Among them, titanium dioxide has reached 120,000 tons, and its export volume has ranked first in the country for three consecutive years. The annual production capacity of the main titanium dioxide is 600,000 tons, ranking first in Asia and fourth in the world.