Sulfur‐substituted nucleobases (i.e., thiobases) are a prospective class of compounds for clinical and cosmetic topical phototherapies. Recent investigations of several thiobases have revealed the ultrafast and efficient population of reactive triplet states upon ultraviolet‐A (UVA) irradiation and the subsequent generation of singlet oxygen in high yield. In this contribution, we examine the photosensitizing activities of three of the most promising thiobase derivatives discovered to date: 2,4‐dithiothymine, 2,4‐dithiouracil, and 2,6‐dithiopurine. These derivatives are shown to decrease the proliferation of human epidermoid carcinoma cells by up to 63 % in vitro, only upon activation with a low dose of UVA radiation (5 J cm⁻²). The generation of reactive oxygen species plays a minor role in the mode of action, suggesting these dithiobases may be effective within oxygen‐deficient environments. Importantly, the photosensitized activity correlates with the magnitude of the triplet lifetime, which should guide the molecular design of next‐generation photodynamic agents.

中文翻译：

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二硫代去核糖核酸酶作为有效的抗人表皮样癌细胞的光动力剂。

硫取代的核碱基（即硫代碱）是用于临床和美容局部光疗的前瞻性化合物。最近对几种硫代碱的研究表明，在紫外线-A（UVA）辐照下，随后的高产单线态氧的生成具有超快而有效的反应性三重态态种群。在这项贡献中，我们研究了迄今为止发现的三种最有希望的硫代碱衍生物的光敏活性：2,4-二硫代胸腺嘧啶，2,4-二硫代尿嘧啶和2,6-二硫代嘌呤。这些衍生物显示出只有在低剂量的UVA辐射（5 J cm ^-2）激活后，才能在体外将人表皮样癌细胞的增殖最多降低63％。）。活性氧的生成在作用方式中起着较小的作用，表明这些二硫代碱可能在缺氧的环境中有效。重要的是，光敏活性与三重态寿命的大小有关，这将指导下一代光动力剂的分子设计。