In recent years, titanium dioxide (TiO2) has gained immense popularity across various industries due to its excellent properties, such as high opacity, brightness, and ultraviolet light absorption. As a result, the demand for titanium dioxide has increased significantly, prompting a surge in the number of manufacturers hoping to capitalize on this booming market. While quality remains a priority, cost-effectiveness has emerged as a crucial factor for consumers, leading to a growing interest in cheap titanium dioxide manufacturers.

Both P25TiO₂NPs (with or without vitamin B2) were not found beyond the epidermis in 99% of the analyzed TEM images (Fig. 8). This is coherent with previous findings showing that nanoparticles greater than 50 nm can not penetrate the skin, even in vivo models with movement, stretching, and friction [54]. However, in one of the zones, a few nanoparticles were observed inside a hair follicle. This could be due to the follicle exposure after the localized rupture of this physical barrier when rats were shaved in order to clean the area for cream topical administration. This finding suggests that nanoparticle-based sunscreen should not be applied on recently shaved or harmed skin, in order to avoid nanoparticle skin penetration.