Gel Based Sunscreen Containing Surface Modified TiO₂Obtained by Sol-Gel Process: Proposal for a Transparent UV Inorganic Filter

Inorganic UV filters, as titanium dioxide (TiO 2 ), have become attractive because of their role in protecting the skin against the damage caused by the continuous exposure to the sun. However, their high refractive index, responsible for a white residue when applied on the skin, has led to the development of alternative inorganic materials, such as TiO 2 nanoparticles. Thus, the aim of this study was the development of transparent and stable gel formulations containing surface modified TiO 2 nanoparticles for application in sunscreens. Also, the physical and chemical properties of formulations containing TiO 2 nanoparticles were evaluated. The UV absorption spectroscopy analyses indicated that the formulations containing TiO 2 nanoparticles had a broad protection spectrum. The diffuse reflectance spectroscopy revealed that the use of PTSH surface modified TiO 2 nanoparticles improved the transparency of the sunscreen formulations compared to that containing commercial ones. The rheology analyses showed that the amount of nanoparticles incorporated in the formulations influences the gel-like or liquid-like behavior. The results showed that the surface modified TiO 2 nanoparticles are a promising innovative UV filter and the formulations containing these nanoparticles are interesting candidates for being used as sunscreen.