Photodynamic therapy (PDT), as an efficient treatment method, has the advantages of low toxicity, non-invasiveness and controllability, which has been widely used in the treatment of proliferative skin diseases and tumors. However, the reported PDT photosensitizers still face many challenges in practical biological applications, such as the efficacy of PDT is significantly reduced by the tumor hypoxic environment; the poor targeting of photosensitizers can easily cause damage to normal tissues. In order to solve the above problems, researchers have proposed many effective strategies to improve the therapeutic efficacy of organic photosensitizers. Herein, the structure and property regulation strategies of organic photosensitizers are reviewed. In addition, the practical applications of photosensitizers in antitumor, antibacterial therapy, and afterglow imaging are introduced. In the end, the design strategies of organic small molecule photosensitizers are summarized and prospected in order to promote the development of this field. Keywords photosensitizers; organic dyes; photodynamic therapy; theranostics; imaging 1 引言 在过去几十年中, 由于光动力疗法(Photodynamic Therapy, PDT)较其他治疗方式具有创伤性小、低毒性、 不易引起耐药性等优点, 在肿瘤、细菌感染等多种疾病 治疗上发挥重要作用 [1][2][3] . 一般来说, 光动力疗法由光 源、 氧气和光敏剂三要素组成 [4] . 其中, 光敏剂是最主要 的元素, 在 PDT 过程中起决定性作用, 光敏剂本身没有 毒性, 但在光和氧分子存在的情况下, 它可以产生活性 氧(Reactive Oxygen Species, ROS), 对核酸、细胞膜和细 胞器等造成损伤, 从而对病灶起到杀伤效果 [5][6][7] . 根据光 敏剂与氧气的作用机理的不同, PDT 疗法可以分为两种 类型 [8] (I 型和 II 型, 图 1). 对于 I 型 PDT 疗法, 基态光 敏剂(S 0 )可以吸收光子, 使电子跃迁至激发单重态(S 1 ), 并通过系间窜越(ISC)跃迁到长寿命的激发三重态(T 1 ), 将电子或质子转移到细胞内底物, 形成阳离子或阴离子 自由基, 随后与分子氧(O 2 )反应生成具有细胞毒性的
