Advancing Melanin Structure and Function through Synthesis and Biomedical Application

McCallum, Naneki C.

doi:https://doi.org/10.21985/n2-3g4d-j381

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Advancing Melanin Structure and Function through Synthesis and Biomedical Application

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Melanin is a functional biopolymer most commonly associated with human skin pigmentation, where it serves as a radiation protection agent, shielding us from the harmful effects of UV radiation. However, melanin is also present in human ears, eyes, hair, and brains, serving a variety of functions. In fact, melanin has seemingly countless functions in the natural world, and is present in almost every type of organism on Earth. From bright colors found in bird feathers, to black fungal cell walls, melanin production has evolved as an ornamental and protective biomaterial capable of toxin adsorption, metal chelation, thermoregulation, radiation protection, and more. Inspired by the possibilities of synthetic melanin constructs as functional biomaterials, we sought to synthesize, characterize, and test artificial analogues of melanin, using new and existing chemistries, and apply them as protection and coloration agents. We created a library of analogues of eumelanin, the common type of melanin in humans, with not only spherical but also rod-like morphology, mimicking a structure found in birds. These were biocompatible with human skin cells, despite having such drastically different morphologies than the natural system. We also synthesized mimics of fungal allomelanins which are chemically distinct from human melanins and showed that these allomelanins are biocompatible with human cells and can protect them from UV radiation. In an even more unusual application, we synthesized various morphologies of allomelanin particles with intrinsic and induced porosity, applied them as fabric coatings, and showed that they can adsorb harmful toxins which can irritate the skin, adding another approach to skin protection through protective clothing. Melanin mimics was also tested to determine their use as artificial tanning and radiation protection agents, exploring monolayer cell culture, 3D reconstructed skin mimics, and intact skin. The materials minimized the harmful effects of UV radiation when applied topically to human skin, and they also showed promise for mitigating the effects of UV and chemical injury in mice. This work highlights the possibilities of artificial melanins as biocompatible, nature-inspired materials for skin protection from radiation and toxins, and paves a pathway for further investigation into melanin for a variety of applications.

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