Photoprotection: extending lessons learned from studying natural sunscreens to the design of artificial sunscreen constituents

Abstract

Evolution has ensured that plants and animals have developed effective protection mechanisms against the potentially harmful effects of incident ultraviolet radiation (UVR). Tanning is one such mechanism in humans, but tanning only occurs post-exposure to UVR. Hence, there is ever growing use of commercial sunscreens to pre-empt overexposure to UVR. Key requirements for any chemical filter molecule used in such a photoprotective capacity include a large absorption cross-section in the UV-A and UV-B spectral regions and the availability of one or more mechanisms whereby the absorbed photon energy can be dissipated without loss of the molecular integrity of the chemical filter. Here we summarise recent experimental (mostly ultrafast pump-probe spectroscopy studies) and computational progress towards unravelling various excited state decay mechanisms that afford the necessary photostability in chemical filters found in nature and those used in commercial sunscreens. We also outline ways in which a better understanding of the photophysics and photochemistry of sunscreen molecules selected by nature could aid the design of new and improved commercial sunscreen formulations.

Study of the colloidal stability and optical properties of sunscreen creams

“…The excessive sun exposure causes cellular damage and immune system function modifications 1,2 . These damaging biological effects are caused by ultraviolet radiation (UV), which is responsible for the photochemical reactions in the human organism.…”

Exploring Norrish type I and type II reactions: an ab initio mechanistic study highlighting singlet-state mediated chemistry

“…Such a process would commonly be termed photostability, and is a desirable photophysical outcome in many bio-organic molecules. 9,[61][62][63] Outcomes such as those exemplified by products (1) . All three profiles exhibit potential barriers.…”

The synthesis of a DHAD/ZnAlTi-LDH composite with advanced UV blocking and antibacterial activity for skin protection

“…Antibacterial photocatalytic therapy (APCT), an alternative solution to traditional antibiotics, has been reported in recent years. 8 Different from traditional antibiotics, APCT employs photocatalysts to split water and oxygen to generate a myriad of reactive oxygen species (ROS), such as hydroxyl radicals (cOH) and singlet oxygen ( 1 O 2 ), which can react with the protein, lipid, polysaccharide of bacteria membrane and lead to bacterial perforation and death. 9 Previous works commonly utilized metal-based photocatalysts, such as CdS/TiO 2 , WO 3 /TiO 2 , BiVO 4 /WO 3 , 10,11 however, heavy metal species in the photocatalysts would induce the risk of toxicity, which limited their further application.…”