Propolis inspired sunscreens for efficient UV-protection and skin barrier maintenance

The direct use of naturally occurring, small molecular ingredients in bioinspired sunscreens has raised several concerns due to the instability, photocytotoxicity, and potential blood toxicity of those ingredients. In this work, we have employed natural ultraviolet (UV)-blocking molecule caffeic acid phenethyl ester (CAPE) from propolis to prepare poly(CAPE) nanoparticles (NPs) as the main bioactive ingredient to fabricate propolis-inspired hydrogel sunscreens. Compared with small molecular CAPE, poly(CAPE) NPs exhibited better dispersion and stability in water, as well as lower physiological toxicity and skin permeability. And the resulting composite hydrogels demonstrated promising properties including water-resistant whereas can be easily erased by warm water as well as safety when interacting with skin. More importantly, the hydrogel sunscreens showed excellent UV protection properties both in vitro and in vivo, and the positive effects in maintaining skin barrier functions. This work provides new strategies towards the facile construction of nature-inspired robust sunscreens in the future.