Bioinspired Chemoenzymatic Route to Artificial Melanin for Hair Pigmentation

Abstract

Recent reports suggest that next-generation hair dyes might take inspiration from the natural pigment melanin. In humans, melanin imparts color to hair and skin and acts as a natural sunscreen and radical scavenger, thereby protecting lipids and proteins from damage. The most commonly employed synthetic mimic of melanin is polydopamine, and its successful deposition on human hair was recently reported. Herein, we describe an enzymatic approach to synthetic melanin for dyeing human hair in a process that closely mimics part of natural melanogenesis. This chemoenzymatic method avoids the addition of a base and enables the implementation of several monomers beyond dopamine, including tyrosine, tyramine, and their derivatives. Critically, the enzyme provides a milder process for producing coated hair fibers than conventional chemical hair dyeing methods. In addition to providing natural coloration, these coatings have the potential to act as protective sunscreens that prevent photodamage of the inner hair fibers during exposure to sunlight. The protocols developed herein represent a mild and efficient route to nature-inspired multifunctional coatings. Such materials are promising candidates for artificial hair pigmentation and, more generally, could find extensive application as functional fiber coatings.