Realizing Near-Infrared (NIR)-Triggered Type-I PDT and PTT by Maximizing the Electronic Exchange Energy of Perylene Diimide-Based Photosensitizers

Development of near-infrared (NIR) Type-I photosensitizers is attracting tremendous attention to overcome the limitation of traditional O2-dependent Type-II photosensitizers, but huge challenges remain. Herein, a promising concept was put forward by lowering the energy of the lowest triplet excited state (T1) of the photosensitizer below the threshold for oxygen sensitization via maximizing the electronic exchange energy. By taking advantage of the low energy intramolecular charge transfer (ICT) state, pyrrolidine as an electron donor is conjugated at the bay position of perylenediimide (PDI) to produce PDIPy that acts as a novel photosensitizer with NIR absorbance and low T1 energy level. With the application of PDIPy, Type-I PDT is realized via effective generation of O2• –. Supramolecular nanoparticles (NanoPDIPy) assembling from PDIPy showed excellent in vitro and in vivo phototherapeutic efficacy against cancer in either normoxia or hypoxia upon 730 nm laser irradiation.