Photodynamic therapy (PDT) through the generation of singlet oxygen utilizing photosensitizers (PSs) is significantly limited under hypoxic conditions in solid tumors. So it is meaningful to develop effective PSs which can maintain excellent therapeutic effects under hypoxia. Here we reported a coumarin-modified cyclometalated Ru(II) photosensitizer (Ru2), which exhibits lower oxidation potential and stronger absorption in the visible region than the coumarin-free counterpart. The evaluation of the PDT effect was performed under both normoxia and hypoxia. The results showed that Ru2 has a better therapeutic effect than the coumarin-free counterpart in in vitro experiments. Especially under hypoxia, Ru2 still retained an excellent PDT effect, which can be attributed to the direct charge transfer between the excited PS and an adjacent substrate through a type I photochemical process, forming highly-oxidative hydroxyl radicals to damage tumor cells. The anti-tumor activity of Ru2 was further proven to be effective in tumor-bearing mice, and tumor growth was inhibited remarkably under PDT treatment.

中文翻译：

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通过I型光化学过程使用环金属化Ru（II）光敏剂在常氧和低氧条件下实现有效的光动力疗法

在实体肿瘤中，在低氧条件下，通过利用光敏剂（PSs）产生单线态氧的光动力疗法（PDT）受到显着限制。因此，开发在缺氧条件下保持优异治疗效果的有效PSs具有重要意义。在这里，我们报道了一种香豆素修饰的环金属化Ru（II）光敏剂（Ru2），与不含香豆素的对应物相比，在可见光区域具有更低的氧化电位和更强的吸收能力。在常氧和低氧下均进行了PDT效果的评估。结果表明，在体外实验中，Ru2的治疗效果优于无香豆素的治疗效果。尤其是在缺氧的情况下，Ru2仍然保留了优异的PDT效果，这可以归因于激发的PS和相邻底物之间通过I型光化学过程进行的直接电荷转移，形成了高度氧化性的羟基自由基，从而损害了肿瘤细胞。进一步证明Ru2的抗肿瘤活性在荷瘤小鼠中是有效的，并且在PDT处理下显着抑制了肿瘤的生长。