TiO2 nanoparticle-embedded starch-tannin biocomposites with efficient UV-shielding and ROS elimination as Pickering emulsifier for bio-safe sunscreen

Inorganic nanoparticles with excellent anti-ultraviolet ability such as titanium dioxide (TiO 2 ) are extensively utilized in sunscreens to protect against UV-induced skin photodamage and carcinogenesis. However, conventional TiO 2 nanoparticles exhibit inherent photocatalytic activity that generates harmful reactive oxygen species (ROS), which limits their applications as sunscreen. In this work, we firstly apply polysaccharide-polyphenol interaction to the sunscreen application of inorganic UV filters (named TiO 2 -TA-CS). Because of the synergistic effect of corn starch (CS) in enhancing TiO 2 nanoparticles dispersion and blocking ROS, TiO 2 -TA-CS exhibit the enhanced UV absorption and leverages tannic acid (TA) to achieve complete eradication of hydroxyl radicals and superoxide radicals generated by TiO 2 nanoparticles, which superiors to the previous reports of bio-safe sunscreen. Furthermore, the UV absorption capacity of TiO 2 -TA-CS Pickering emulsions is increased by a factor of 2.5 and there is no obvious cytotoxicity in the UV evaluation. Compared with commercial sunscreens, it has lower UV penetration rate and higher SPF value. In vitro studies and cell viability assays collectively confirm the excellent efficacy of the formulated sunscreen in mitigating photoaging and protecting skin cells against UV-induced damage. Therefore, the TiO 2 -TA-CS Pickering emulsions exhibit favorable biocompatibility, high UV protection, and human skin safety, providing a new strategy for sun protection and other medical applications.