Imprinting Synthetic Polyphenols on Hair and Their Progressive Oxidative Browning

The astringent tastes of wine or green tea and the spiciness of capsaicin persist on the tongue due to their strong binding to mucosal proteins, making them difficult to remove by rinsing. Polyphenols in those plants, in general, robustly bind with proteins exhibiting non-washable and water-resistant coating properties. In this study, we introduce a imprintably strong, non-washable synthetic polyphenols for hair browning through in situ spontaneous polyphenol oxidation under washable conditions. Specifically, a synthetic polyphenol, dimeric 1,2,4-benzenetriol (diBTO), demonstrates an immediate and rapid adherence to hair keratin, forming a non-washable polyphenol layer resistant against detergent washing. The nearly imprinted polyphenols on the hair surface can undergo progressive further oxidation, resulting in gradual color development, which is similar browning phenomenon shown in apples and bananas. Moreover, Cu(II) ions serve as crucial and responsive coordinating linkers between diBTO ligands, significantly increasing the amount of diBTO adhesion and resulting in a rich brown polyphenolic color. Cysteine on the hair surface also acts as an extra ligand to facilitate rapid adhesion between the hair surface and the polyphenol ligand. This study reduces the long exposure time required for dyeing in professional settings, a routine aspect of traditional hair dyeing methods, and demonstrates that gray hair care can be effectively managed through Cu(II)-dependent polyphenol browning in everyday life. Furthermore, this innovative polyphenol implantation holds significant potential for future applications, including immediate use in 3D scaffolds for controlling the wettability of porous surfaces and introducing responsive polymers, underscoring its versatility and broad applicability across various fields.