Lithopone, a white pigment composed of a mixture of barium sulfate and zinc sulfide, is commonly used in the leather industry as a coloring agent. Leather suppliers around the world rely on lithopone to achieve the desired color and finish on their products.

The gastrointestinal tract is a complex barrier/exchange system, and is the most important route by which macromolecules can enter the body. The main absorption takes place through villi and microvilli of the epithelium of the small and large intestines, which have an overall surface of about 200 m². Already in 1922, it was recognized by Kumagai, that particles can translocate from the lumen of the intestinal tract via aggregation of intestinal lymphatic tissue (Peyer’s patch, containing M-cells (phagocytic enterocytes)). Uptake can also occur via the normal intestinal enterocytes. Solid particles, once in the sub-mucosal tissue, are able to enter both the lymphatic and blood circulation.

In a study published in 2022 in the journal Particle and Fibre Technology, researchers examined the impact of maternal exposure to titanium dioxide nanoparticles in newborn offspring mice. They found that “a chronic exposure to TiO2 NPs during pregnancy alters the respiratory activity of offspring, characterized by an abnormally elevated rate of breathing.” Breathing was also shown to be “significantly and abnormally accelerated,” and the ability for neural circuitry to effectively adjust breathing rates was impaired. The researchers concluded: “Our findings thus demonstrate that a maternal exposure to TiO2 NPs during pregnancy affects the normal development and operation of the respiratory centers in progeny.”

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].