The vitaminC@P25TiO2NPs, on the other hand, were obtained through an optimized method based on Mallakpour et al. [27]. Initially, 0.02 g of P25TiO2NPs were dispersed in 1 mL of ultrapure water and stirred in a Vortex. Next, 100 μL of HCl (0.01 M) were added (pH 2) to 100 uL of P25TiO2NPs to avoid gel formation. Then, 100 μL of vitamin C dissolved in ultra-pure water (5.0 × 10−3 M) solution were added to the mixture and was ultrasonicated for 30 min. Finally, vitamin C was added in excess to gain a beige-orange color suspension, and the ultrasonication continued for another 30 min. The pellet obtained after centrifuging the suspension for 10 min at 4500 rpm was resuspended in ultrapure water, centrifuged again, and then lyophilized.
During times of economic growth, demand for consumer goods that use titanium dioxide, such as paint and plastics, tends to increase, leading to higher prices During times of economic growth, demand for consumer goods that use titanium dioxide, such as paint and plastics, tends to increase, leading to higher pricestitanium dioxide price per ton. Conversely, during economic downturns, demand may decrease, resulting in lower prices.In the application of lithopone in ink industry, lithopone has fine particles, loose structure, good fineness and good paint adhesion, so it can be well combined with other colors in the composition of ink.
As mentioned above, these oxide NPs are harmful in part because both anatase and rutile forms are semiconductors and produce ROS. Particularly, P25 kind has band-gap energies estimated of 3.2 and 3.0 eV, equivalent to radiation wavelengths of approximately 388 and 414 nm, respectively. Irradiation at these wavelengths or below produces a separation of charge, resulting in a hole in the valence band and a free electron in the conduction band, due to the electron movement from the valence to conduction bands. These hole–electron pairs generate ROS when they interact with H2O or O2 [43,44]. It was described that they can cause an increase in ROS levels after exposure to UV-visible light [45]. The NBT assay in the studied samples showed that bare P25TiO2NPs produce a large amount of ROS, which is drastically reduced by functionalization with vitamin B2 (Fig. 5). This vitamin, also known as riboflavin, was discovered in 1872 as a yellow fluorescent pigment, [46] but its function as an essential vitamin for humans was established more than sixty years later, and its antioxidant capacity was not studied until the end of the XX century [47,48]. This antioxidant role in cells is partially explained because the glutathione reductase enzyme (GR) requires it for good functionality. This enzyme is the one in charge of the conversion of oxidized glutathione to its reduced form which acts as a powerful inner antioxidant and can quench the ROS [49,50]. The cost of this action is that the glutathione is converted to the oxidized form and needs to be recovered by the GR. Consequently, the cells need more vitamin B2. Another glutathione action is the protection against hydroperoxide. This activity is also mediated by riboflavin. Therefore, local delivery of this vitamin seems to significantly help the cells in their fight to keep the oxidative balance, once they are exposed to high levels of ROS.
Although the evidence for general toxic effects was not conclusive, on the basis of the new data and strengthened methods we could not rule out a concern for genotoxicity and consequently we could not establish a safe level for daily intake of the food additive, commented Matthew Wright, member of the EFSA's Food Additives and Flavourings Panel in a press statement.