Recent Advances in Development of NIR-II Fluorescent Agents

In the past decade, biological imaging in the second near infrared (NIR-II) window has emerged as a promising imaging method to visualize deep-tissue anatomical structures and profile internal physiological status. Owing to advantages in reduced light absorption, suppressed photon scattering, and minimized interference from tissue autofluorescence, NIR-II imaging presents advantages on improved penetration depth and high spatial resolution, opening up wide opportunities to unmask the underlying mechanisms of various physiological processes. An ideal NIR-II fluorophore for in vivo fluorescence imaging should have high quantum yields, red-shifted emission wavelengths as well as favorable pharmacokinetic properties in order to afford high imaging quality, monitor dynamic physiological process in real time, and mitigate safety concerns. Here, in this chapter, we summarize recent advances in rational design and optimization of NIR-II fluorescence imaging agents with superior properties as mentioned above, present their applications, and offer our opinions on the unique potentials of these imaging agents for future clinical translation.