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.

CNNC Huayuan Titanium Dioxide Co., Ltd. (hereinafter referred to as the company or CNNC TiO2 is a famous titanium dioxide manufacturer in China and a listed company on the Shenzhen Stock Exchange. Its main products are high-grade rutile titanium dioxide, which are widely used in coatings, plastics, rubber, In ink, paper and other fields, it is known as “industrial monosodium glutamate”, and its application prospects are very broad.

Titanium dioxide prices climbed significantly in the European region during Q2 2021, owing to strong demand from the downstream sector. Major global suppliers indicated that they have seen a surge in its demand for primarily from Europe and Asia, despite a global supply constraint. Furthermore, a global player raised titanium dioxide costs in Europe by 200 USD /MT this quarter, effective Q3 2021.