Recent advances in the design and applications of near-infrared II responsive small molecule phototherapeutic agents

NIR-II phototherapeutic agents possess the advantages of NIR-II optical imaging and phototherapy, which include high signal-to-noise ratio imaging and non-invasive treatment mode. These features have attracted widespread attention to the use of phototherapeutic agents in the treatment of various diseases. Recent studies have demonstrated the effectiveness of various NIR-II fluorophores derived from traditional dyes, including cyanine dyes, rhodamines, boron dipyrromethene (BODIPY) and BBTD-based dyes, for imaging-guided photodynamic, photothermal and combined/synergistic therapies. This review contains descriptions of typical small molecule NIR-II dyes that have been developed for use as phototherapeutic agents, along with principles for their design and their applications in biomedicine. Strategies devised to enhance the phototherapeutic performances of these agents are elaborated, and challenges facing and prospects for the clinical translation of NIR-II dyes are also discussed. We hope that this review will serve as both a reference source for studies conducted thus far and an inspiration for designing new high-performance multifunctional NIR-II dyes, and promoting their clinical translation.