Stable Alkyne-Bridged Conjugated Polymer Nanoparticles With a High NIR-II Photothermal Conversion Efficiency of 71% for Effective Photothermal Tumor Therapy

Organic photothermal materials (PTMs) in the near-infrared (NIR) range (1000–1700 nm) are more favorable for photothermal therapy (PTT) therapeutic applications because of their greater depth of tissue penetration and better biosafety. However, the photothermal conversion efficiency (PCE) of the few NIR-II-responsive organic PTMs that have been investigated is still slightly low. Here, a stable alkyne-bridged conjugated polymer, BBT-BTE, are explored with a high PCE for tumor ablation within the NIR-II window. The BBT-BTE synthesized by the Stille coupling reaction has strong NIR-II absorption, and their nanoparticles (NPs) achieved a 71% PCE under 1064 nm laser excitation, with good photothermal stability. BBT-BTE NPs are shown to be effective in completely ablating tumors without any recurrence in both in vitro and in vivo experiments. Additionally, the biosafety of these NPs is further proven by biochemical analysis and tissue biopsy. This study developed a high-performance NIR-II PTM and offered practical and feasible insights into the design of efficient photothermal materials specifically for the NIR-II window.