Organic Molecules: Desirable Candidates for NIR-II Window Bioimaging

The second near infrared (NIR-II) window in optical wavelength of 1000–1700 nm have become a hot topic in bioimaging, especially in vivo imaging. Compared to the first near infrared (NIR-I) window (700-900 nm), NIR-II fluorescence imaging has advantages including low auto-fluorescence, high signal-to-background ratio, deep penetration, and high resolution. Among many fluorescence imaging constracting agents, organic probe has benefits of low toxicity, easy structure tunability, high excretion rate, and good biocompatibility. Meanwhile, conjugated polymer nanoparticles can also be used in photoacoustic imaging. This review focuses on recent progress in development of NIR-II probe in optical imaging and photoacoustic imaging. (paper)