Conjugated Polymer Coupled with Nonconjugated Segments for NIR-II Fluorescence/NIR-II Photoacoustic Imaging-Guided NIR-II Photothermal Therapy

Development of conjugated polymer-based water-soluble nanoparticles (NPs) for second near-infrared fluorescence (NIR-II FL, 1000–1700 nm) and NIR-II photoacoustic (PA) imaging-guided NIR-II photothermal therapy (PTT) is expected to gain favor in clinical anticancer applications. However, integrating these imaging and therapeutic functions into a single NIR-II absorption conjugated polymer BTC12 is a major challenge to accurately balance the nonradiative and radiative decay pathways. Herein, an NIR-II absorption conjugated polymer was designed and synthesized by coupling flexible nonconjugated segments into a polymer backbone to simultaneously achieve NIR-II FL, NIR-II PA imaging, and NIR-II PTT. The developed conjugated polymer-based water-soluble NPs (BTC12 NPs) showed satisfactory functionality with a promising photothermal conversion efficiency of 46.8%. An in vivo study demonstrated that BTC12 NPs can accurately acquire the tumor location and size via NIR-II FL/NIR-II PA imaging. Furthermore, BTC12 NPs showed marked antitumor efficacy by NIR-II PTT upon 1064 nm laser irradiation. This work provides a perspective for the design of multifunction conjugated polymers for NIR-II FL/NIR-II PA imaging-guided NIR-II PTT applications.