Development of an Antioxidant and UV-Shielding Composite Hydrogel Using Mussel-Inspired Cellulose Nanocrystals, Polydopamine, and Poly(vinyl alcohol) for Application in Sunscreens

Sunscreens can help protect the skin from solar ultraviolet (UV) radiation, which is harmful to human health. However, traditional sunscreens can penetrate the skin, raising concerns about their safety. Therefore, fabrication of a sunscreen with biocompatible, UV-shielding, and antioxidant properties is pertinent. Herein, a simple method involving the self-polymerization of dopamine to polydopamine (PDA) was proposed for the surface modification of poly(vinyl alcohol) (PVA) and cellulose nanocrystals (CNCs) to fabricate cellulose nanocrystal/polydopamine/poly(vinyl alcohol) (CNC/PDA/PVA) hydrogels. Compression tests revealed that the CNC/PDA/PVA hydrogel had a compression strength of 5.0 MPa. After UV exposure for 2400 h, the compression strength of the PVA hydrogel decreased markedly from 3.5 to 1.5 MPa, whereas that of the CNC/PDA/PVA hydrogel decreased slightly from 5.0 to 4.8 MPa. Mouse embryonic fibroblast (NIH-3T3) cell experiments showed that the CNC/PDA/PVA hydrogel exhibited excellent biocompatibility. A decrease in the residual 1,1-diphenyl-2-picrylhydrazyl (DPPH) content from 100.0% to 4.0% implied a strong antioxidant capacity of the CNC/PDA/PVA hydrogel. Notably, UV–vis spectroscopy analysis and in vivo mouse experiments demonstrated that the CNC/PDA/PVA hydrogel blocked approximately 99.0% of UV light and prevented UV-induced tissue injury, respectively. These results indicate the potential applications of the prepared CNC/PDA/PVA hydrogel as a UV absorber in next-generation antioxidative and UV-shielding materials.