Research Highlight: Gianneschi
Synthetic Melanin Hair Dye
Human hair is naturally colored by melanin pigments, which aﬀord myriad colors from black, to brown, to red depending on the chemical structures and speciﬁc blends. Reduction or disappearance of melanins from hair ﬁbers is the phenomenon that leads to color loss and subsequent hair greying and eventual whitening. Despite recent studies reporting the potential carcinogenicity of certain conventional hair dye components, frequent development of allergies in clients and colorists, and dye-induced hair damage, the use of small molecule-based dyes continues.
In recent decades, synthetic eﬀorts to develop mimics of natural melanin have centered on dopamine oxidation to polydopamine. To date, only a few attempts at polydopamine deposition on human hair have been reported, and their translation to widespread usage and potential commercialization is hampered by the conditions employed. In this work, we developed conditions for depositing synthetic melanin on hair and we demonstrated that we could substitute mild heat and a small amount of base for the heavy metals and strong oxidants used in prior methods. This approach allowed access to colors from brown/black to red/gold shades. Overall, the conditions were similar or milder than those used for commercially available, permanent hair dyes. The synthetic melanin was designed to deposit on the hair surface, which is less likely to cause damage of the inner cortex. Such colored coatings persisted for at least 18 washes, competing well with current, permanent hair dyes.
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