Development of small-molecule NIR-II photothermal agents for image-guided tumor therapy

Small-molecule photothermal agents (PTAs) working in second near-infrared (NIR-II) region exhibited a great potential of cancer treatment and diagnosis for the advantages of minimal side effect , deeper penetration ability of tissue, and easily adjustable of structure. Various small-molecule PTA that integrate NIR-II fluorescence/photoacoustic (PA) imaging and thermal effect can visualize tumor locations and thermally irradiate tumor in real time, holding significant potential for early diagnosis and precision treatment of cancer. In this review, we summarize various strategies to improve the photothermal therapy (PTT) effects of small-molecule PTAs for NIR-II imaging-guided cancer treatment, including the enhancement of photothermal conversion efficiency (PCE) and photostability, the improvement of biocompatibility and specificity, and the facilitation of PTT by synergistic therapy . The perspectives and obstacles associated with NIR-II small-molecule PTAs for application are also discussed. In this review, we summarized recent advancements in NIR-II small molecule photothermal agents for imaging-guided tumor therapy, focusing on various strategies affecting and improving PTT, as well as potential challenges and future prospects. • Advances in NIR-II organic small-molecule as PTAs for imaging guided PTT. • Introduced different strategies for the improvement of photothermal conversion efficiency of PTAs. • Summarized the different strategies for facilitating PTT of NIR-II organic small-molecule PTAs. • Discussed challenges and future prospects for NIR-II organic small-molecule PTAs.