Small Molecular NIR-II Fluorophores for Cancer Phototheranostics

Phototheranostics integrates deep-tissue imaging with phototherapy (containing photothermal therapy and photodynamic therapy), holding great promise in early diagnosis and precision treatment of cancers. Recently, second near-infrared (NIR-II) fluorescence imaging exhibits the merits of high accuracy and specificity, as well as real-time detection. Among the NIR-II fluorophores, organic small molecular fluorophores have shown superior properties in the biocompatibility, variable structure, and tunable emission wavelength than the inorganic NIR-II materials. What's more, some small molecular fluorophores also display excellent cytotoxicity when illuminated with the NIR laser. This review summarizes the progress of small molecular NIR-II fluorophores with different central cores for cancer phototheranostics in the past few years, focusing on the molecular structures and phototheranostic performances. Furthermore, challenges and prospects of future development toward clinical translation are discussed.