Donor-Acceptor Modulating of Ionic AIE Photosensitizers for Enhanced ROS Generation and NIR-II Emission.

Photosensitizers (PSs) with aggregation-induced emission (AIE) characteristics are competitive candidates for bioimaging and therapeutic applications. However, their short emission wavelength and nonspecific organelle targeting hinder their therapeutic effectiveness. Herein, a donor-acceptor modulation approach is reported to construct a series of ionic AIE photosensitizers with enhanced photodynamic therapy (PDT) outcomes and fluorescent emission in the second near-infrared (NIR-II) window. By employing dithieno[3,2-b:2',3'-d]pyrrole (DTP) and indolium (In) as the strong donor and acceptor, respectively, the compound DTP-In exhibits a substantial redshift in absorption and fluorescent emission reach to NIR-II region. The reduced energy gap between singlet and triplet states in DTP-In also increases the reactive oxygen species (ROS) generation rate. Further, DTP-In can self-assemble in aqueous solutions, forming positively charged nanoaggregates, which are superior to conventional encapsulated nanoparticles in cellular uptake and mitochondrial targeting. Consequently, DTP-In aggregates show efficient photodynamic ablation of 4T1 cancer cells and outstanding tumor theranostic in vivo under 660 nm laser irradiation. This work highlights the potential of molecular engineering of donor-acceptor AIE PSs with multiple functionalities, thereby facilitating the development of more effective strategies for cancer therapy.