Multifunctional TiO2/SBA-15 mesoporous silica hybrids loaded with organic sunscreens for skin application: The role in photoprotection and pollutant adsorption with reduced sunscreen permeation.

TiO2 acts as an inorganic sunscreen and photocatalyst to protect humans from environmental pollutants. We incorporated TiO2 into mesoporous silica (SBA-15) for skin application to prevent environmental stresses including UVA irradiation and pollutant invasion. Organic ultraviolet (UV)A filters such as avobenzone and oxybenzone were then loaded into mesoporous support for synergistic sunscreen efficiency. The as-prepared formulations with different TiO2 amounts (10 %-50 %) were fabricated. The pore size decreased from 4.72 to 4.00 nm following the increase in TiO2 percentage. TiO2/SBA-15 captured about 60 % fluoranthene and 80 % furfural within 3 h with no significant difference due to different TiO2 content. The in vitro photoprotection assessed by UVA/UVB ratio exhibited the increase in Boots star rating from 2 to 3 to 5 by entrapment of avobenzone into TiO2/SBA-15. Thirty-percent TiO2/SBA-15 in hydrogel decreased avobenzone and oxybenzone deposition by 70 % and 80 % compared to free form, respectively. Avobenzone and TiO2 supplementation to SBA-15 significantly alleviated skin cell death and neutrophil recruitment in the photoaged mouse skin compared to the SBA-15 application alone. Compared to the UVA-irradiated skin, 30 % TiO2/SBA-15 showed a 2.5- and 3.1-fold decline in IL-1β and IL-6 levels, respectively. The TiO2/SBA-15 hybrid was considered non-irritant based on results of cytotoxicity assay, skin histology, and cutaneous barrier function. Our data indicate that the versatile mesoporous silica is an effective system for topical use in sunscreen and skin protection.