Orange/red dual-emissive boron- and nitrogen-codoped carbon dots for wash-free and selective staining of lipid droplets in live cells

Lipid droplet (LD) is an organelle that stores lipids and plays crucial roles in many metabolic processes and diseases. However, developing a method for long-term tracing of LDs and monitoring LD movement remains a challenge. Here, by using a solvent-free carbonization method, we prepare a kind of boron- and nitrogen-codoped carbon dots (BNCDs) from 3-aminophenylboronic acid. The as-synthesized BNCDs have an average size of ∼6.9 nm, long-wavelength fluorescence emission, and excitation wavelength-independent fluorescence emission, and can realize wash-free LD imaging without the introduction of LD-targeting ligands. Besides, the BNCDs have the characteristics of good biocompatibility, simple preparation, and low cost. More importantly, the BNCDs can effectively track the dynamic changes of LDs (including lipophagy) in live animal cells. This work shows that the developed BNCDs can be used as an ideal probe for nondestructively visualizing LDs, which may have implications for the future studies on LDs-related metabolism and diseases.