Thermosensitive ZnO-PMMA/PEG microgels: A smart sunscreen with adapting SPF to ambient temperature fluctuations

Abstract

Increasing awareness of the importance of ultraviolet protection has led to the development and utilization of sunscreen products. The sun protection factor (SPF) value of traditional sunscreens is fixed and cannot be flexibly adapted to changing environmental requirements. Herein, we fabricate a series of thermosensitive ZnO-poly (methyl methacrylate)/nonlinear poly(ethylene glycol) (PMMA/PEG) core-shell microgel with different monomer ratios. The PMMA core particle is designed to immobilize ZnO nanoparticles for achieving high loading capacity, and the hydrophilic nonlinear PEG gel shell possesses good biocompatibility and provides adjustable SPF value in response to different environmental conditions. The prepared microgels are monodisperse spherical with a well-defined core-shell morphology. The shell thickness of the microgels can be easily controlled by changing the feeding ratios of shell precursors. The optimized ZnO-PMMA/PEG microgels display significant sun protection properties at a concentration of 10 wt% (SPF 45 ± 5.9, 20 °C) and enhanced UV resistance performance as the temperature increases (SPF 53.1 ± 1.1, 37 °C). Both cell and mouse experiments confirmed the limited skin penetration potential of the microgels and their good compatibility with biological systems. This developed ZnO-PMMA/PEG microgels exhibit promising application potential in intelligent sunscreen technology.