Bioinspired Design of seco ‐Chlorin Photosensitizers to Overcome Phototoxic Effects in Photodynamic Therapy

Photodynamic therapy (PDT) is a non‐invasive treatment modality against a range of cancers and nonmalignant diseases, however one must be aware of the risk of causing phototoxic reactions after treatment. We herein report a bioinspired design of next‐generation photosensitizers (PSs) that not only effectively produce ROS but undergo fast metabolism after treatment to overcome undesirable side effects. We constructed a series of β‐pyrrolic ring‐opening seco ‐chlorins, termed beidaphyrin ( BP ), beidapholactone ( BPL ), and their zinc(II) derivatives ( ZnBP and ZnBPL ), featuring intense near‐infrared absorption and effective O 2 photosensitization. Irradiation of ZnBPL led to a non‐cytotoxic, metabolizable beidaphodiacetamide ( ZnBPD ) via in situ generated O 2 .− but not 1 O 2 , as revealed by mechanistic studies including time‐resolved absorption, kinetics, and isotope labeling. Furthermore, water‐soluble ZnBPL showed an effective therapeutic outcome, fast metabolism, and negligible phototoxic reactions.