Engineered DR/NIR dual-emission carbonized polymer dots for simultaneous tracking of lipid droplets and lysosomes

Developing near-infrared fluorescent probes for simultaneous tracking of lipid droplets (LDs) and lysosomes is highly desirable for studying cell metabolism. In this work, deep-red/near-infrared dual-emission carbonized polymer dots (DN-CPDs) were prepared for ratiometric monitoring of the intracellular polarity. Detailed structural analysis revealed that the deep-red emission and near-infrared peak of DN-CPDs originate from the molecular state and surface state, respectively. The surface-state emission was derived from the intraparticle charge-transfer (ICT) effect of the donor-bridge-acceptor (D-π-A) structure of DN-CPDs. The obtained DN-CPDs exhibited excellent dual-labeling ability, large Stokes shifts, ratiometric polarity sensitivity, high selectivity, and satisfactory photostability. Moreover, with the polarity distinction between LDs and lysosomes, DN-CPDs nanoprobes were successfully used to observe the dynamic changes of the two aforementioned organelles during starvation-induced lipophagy and drug-induced lipophagy inhibition processes. This work not only provides a useful tool for LD-lysosome related studies but is also valuable for the preparation of CPDs with long wavelength emission.