Sustainable and durable color cosmetics: riboflavin phosphate-mediated photo-crosslinked casein films with tannic acid†

The cosmetics industry is increasingly focusing on developing sustainable and environmentally friendly products while maintaining high performance. In color cosmetics, achieving long-lasting durability of water-soluble dyes remains a challenge. This study presents a sustainable approach to enhance the durability of water-soluble dyes in cosmetics using biopolymer-based films. The casein films were fabricated through riboflavin phosphate (RFP)-mediated photo-crosslinking, with tannic acid (TA) incorporated to improve mechanical properties. The fabrication process, characterization, and performance evaluation of the biopolymer-based films were investigated. Fourier-transform infrared spectroscopy (FTIR) and scanning electron microscopy (SEM) analyses confirmed the successful crosslinking and formation of a porous network structure. Rheological measurements revealed that the incorporation of TA significantly enhanced the mechanical strength of the films. Cytocompatibility assessment using NIH/3T3 fibroblasts demonstrated the films’ excellent biocompatibility. The durability and color retention of a water-soluble red dye in the biopolymer-based films were evaluated on human skin. The films formed under blue light irradiation exhibited superior dye retention compared to non-irradiated films, with TA addition providing a minor improvement in durability. This study bridges the gap between cosmetic science and biomaterials research, providing a foundation for future investigations into bio-interactive materials for dermal applications. These findings highlight the potential of RFP-mediated photo-crosslinked casein films as a sustainable and effective solution for enhancing the durability of water-soluble dyes in color cosmetics.