Melanin is a class of ubiquitous, heterogeneous, polymeric pigments. One of the most unusual features of melanin is the presence of stable persistent radicals, which has been reported to relate to ionizing radiation protection, including X-rays and gamma rays. In this work, we aimed to increase the radical content by introducing nitroxide radicals into synthetic melanin nanomaterials. Nanoparticles (NPs) were prepared by copolymerization of a stable radical modified monomer with the monomer dopamine. The radical content increased to 1 order of magnitude higher than that of the conventional melanin-like material, polydopamine. These radical NPs can enter human epidermal keratinocytes and form perinuclear caps, mimicking natural melanin synthesized by melanocytes. We demonstrated that these NPs display protective properties by scavenging reactive oxygen species, one of the most important biological effects of ionizing radiation exposure. This finding may have potential application for materials capable of mitigating side effects of clinical radiation therapy.

中文翻译：

---

富含自由基的人造黑色素

黑色素是一类普遍存在的，非均质的聚合物颜料。黑色素最不寻常的特征之一是存在稳定的持久性自由基，据报道这与电离辐射防护有关，包括X射线和伽马射线。在这项工作中，我们旨在通过将氮氧自由基引入合成黑色素纳米材料中来增加自由基含量。通过将稳定的自由基改性单体与单体多巴胺共聚制备纳米颗粒（NPs）。自由基含量比传统的黑色素样物质聚多巴胺高1个数量级。这些自由基NP可以进入人类表皮角质形成细胞并形成核周帽，模仿由黑色素细胞合成的天然黑色素。我们证明了这些NP通过清除活性氧（电离辐射暴露最重要的生物学效应之一）来显示保护性。这一发现可能对能够减轻临床放射治疗副作用的材料具有潜在的应用价值。