A straightforward strategy to modulate ROS generation of AIE photosensitizers for type-I PDT

Type-I photodynamic therapy (PDT), valued for its reduced oxygen requirement, generates highly cytotoxic •OH radicals. However, conventional strategies for developing type-I photosensitizers (PSs) are complex and involve intricate organic synthesis. Herein, we present a novel strategy to alter the generation of reactive oxygen species (ROS) by simply manipulating the twisting degree of donor–acceptor (D−A) type aggregation-induced emission (AIE) PSs. Specifically, natural saturated fatty acids are employed to modulate the twisting state of AIE PSs, with higher doping ratios yielding more twisted structures and increased type-I ROS generation. In contrast, fatty acids with higher crystallinity promote planar structures and type-II ROS generation. Theoretical calculations suggest that AIE PSs with highly twisted structures lead to a prominent reduction in Δ E ST and effective separation of electron−hole pairs, thereby favoring efficient intersystem crossing and charge transfer. The PDT system primarily driven by type-I ROS exhibits efficient bactericidal activity against clinically drug-resistant bacteria, which remarkably accelerates the recovery of bacteria-infected wounds in mice. This study demonstrates the first example of modulating ROS generation type by manipulating the twisting degree of D−A type AIE PSs, eliminating the need for intricate molecular design and organic synthesis. The proposed strategy opens up new avenues for advancing PDT applications.