Aggregation-Induced Emission Near-Infrared (NIR)-II-Conjugated Polymers Coupled With Nonconjugated Segments for NIR-II Fluorescence Imaging–Guided NIR-II Photothermal Therapy

The development of conjugated polymer–based water-soluble nanoparticles for near-infrared-II (NIR-II) fluorescence (FL; 1000–1700 nm)-guided photothermal therapy holds promise in advancing cancer treatment. However, excessive nonradiative decay leads to almost complete quenching of conjugated polymers’ fluorescence. Therefore, a critical challenge is to suppress nonradiative decay while maintaining high-quality fluorescence imaging and excellent photothermal conversion efficiency. In this study, a series of NIR-II-conjugated polymers with aggregation-induced emission (AIE) effects are designed and synthesized using the Stille coupling reaction. The dual enhancement strategy of modulating the AIE units and introducing non-conjugated backbone into the polymer backbone resulted in BCT1 with a high αAIE value of 3.27. BCT1 nanoparticles exhibit excellent NIR-II fluorescence, a high photothermal conversion efficiency of 70.51%, and a tenfold enhancement in fluorescence compared with BT1. Both in vitro and in vivo experiments validated their good biocompatibility and outstanding performance in NIR-II fluorescence imaging for accurately determining the location of tumors. This study provides a novel strategy and method for designing and developing multifunctional conjugated polymers for NIR-II fluorescence imaging–guided photothermal therapy.