The luminous frontier: transformative NIR-IIa fluorescent polymer dots for deep-tissue imaging

In the realm of deep-tissue imaging, fluorescence imaging in the second near-infrared window (NIR-II, 1000–1700 nm) has proved to be an emerging tool, allowing scientists to probe biological processes with unprecedented depth. Within the NIR-II window, the NIR-IIa region (1300–1400 nm) has proved to have excellent imaging quality in the NIR-II window. Among the diverse types of NIR-II fluorophores, polymer dots (Pdots) have surfaced as a unique category of probes due to their exceptional properties including exorbitant brightness, excellent photostability, outstanding water dispersibility, and facile structural modification compared to traditional fluorescent molecules. The utilization of NIR-IIa Pdots has also addressed critical limitations in imaging by utilizing the advantages of reduced light scattering, diminished autofluorescence, and decreased light absorption by biospecies. Realizing such remarkable characteristics, this review offers insights into the design of high-performance NIR-IIa Pdots through a comprehensive interplay between chemical structures, photophysical properties, and their application in deep-tissue imaging.