UV and dark-triggered repetitive release and encapsulation of benzophenone-3 from biocompatible ZnO nanoparticles potential for skin protection.

The present study reports a UV and dark-triggered highly intelligent drug delivery system for skin protection. ZnO nanoparticles (NPs), a UV filter, were synthesized and characterized to be the carrier for benzophenone-3 (Bp-3), a UV-absorption medicine, by varying the molar ratio of ZnO NPs to Bp-3 ranging from 300 : 1 to 20 : 1. The drug release under three cycles of UV and dark stimulation (each for two hours) and its cytotoxicity to human keratinocyte cells and skin fibroblasts were investigated. SEM studies showed the diameter of ZnO was around 30 to 40 nm, which assembled into loose and large NPs ranging from 500 to 1400 nm. Contact angle tests showed ZnO NPs switched to a more hydrophilic and back to a more hydrophobic state under two hours of UV and dark exposure. The optimized encapsulation efficiency and loading capacity of Bp-3 were 53.68 ± 0.13% and 133.61 ± 0.20% when the molar ratio of ZnO NPs to Bp-3 was 150 : 1 and 80 : 1. The Bp-3 was almost completely released from ZnO NPs under 2 hours of UV radiation and was mostly encapsulated in after 2 hours of dark stay in three cycles of UV and dark exposure. The Bp-3 loaded ZnO NPs showed low cytotoxicity to human keratinocyte cells and human skin fibroblasts. Overall, a UV and dark-triggered repetitively on-demand drug delivery system biocompatible to skin cells and potential for skin protection from UV radiation was developed.