Modulating\nthe γ‑ray Protection Properties\nof Melanin via a Highly Conjugated Catechol Structure

Melanin is a dark pigment found in many organisms that\ninteracts\nwith various forms of electromagnetic radiation, such as X-rays, γ-rays,\nand Ultraviolet visible light, providing protection against radiation\ndamage to the host. The mechanism by which melanin protects against\nionizing radiation involves dissipating energy around the cell nucleus\nto form a perinuclear cap. Additionally, melanin reacts with the free\nradicals produced by the radiolysis of water, quenching reactive oxygen\nspecies. In this study, we introduced a conjugated monomer, hexahydroxytriphenylene\n(HHTP), which has a rigid planar structure, into selenomelanin. The\naim was to increase the physical shielding ability of selenomelanin\nwhile increasing its free radical content. Our findings indicated\nthat incorporating HHTP molecules into selenomelanin effectively increased\nthe unpaired electron content of selenomelanin and protected immortalized\nhuman keratinocyte (HaCaT) cells from 10 Gy γ-rays exposure.\nAdditionally, eumelanin supplemented with HHTP molecules demonstrated\nexcellent biocompatibility and offered similar protection to HaCaT\ncells exposed to 10 Gy γ-rays at high concentrations. This study\nis important for optimizing the functionality of melanin through the\nmodulation of its conjugated structure.