Dual Functional Full-Color Carbon Dot-Based Organelle Biosensor Array for Visualization of Lipid Droplet Subgroups with Varying Lipid Composition in Living Cells

In situ visualization of lipid composition diversity in lipid droplets (LDs) is essential for decoding lipid metabolism and function. However, effective probes for simultaneously localizing and reflecting the lipid composition of LDs are currently lacking. Here, we synthesized full-color bifunctional carbon dots (CDs) that can target LDs as well as respond to the nuance in internal lipid compositions with highly sensitive fluorescence signals, due to lipophilicity and surface state luminescence. Combined with microscopic imaging, uniform manifold approximation and projection, and sensor array concept, the capacity of cells to produce and maintain LD subgroups with varying lipid composition was clarified. Moreover, in oxidative stress cells, LDs with characteristic lipid compositions were deployed around mitochondria, and the proportion of LD subgroups changed, which gradually disappeared when treated with oxidative stress therapeutics. The CDs demonstrate great potential for in situ investigation of the LD subgroups and metabolic regulations.

Automated summary

In this study, bifunctional carbon dots that can target and reflect the lipid composition in lipid droplets (LDs) were synthesized. These carbon dots showed highly sensitive fluorescence signals in response to lipid composition changes in LDs. The capacity of cells to generate and maintain LD subgroups with varying lipid composition was revealed by microscopic imaging and mathematical modeling. Furthermore, LDs with characteristic lipid compositions were observed around mitochondria in oxidative stress cells, and the proportion of LD subgroups changed and gradually disappeared with oxidative stress therapeutics. These carbon dots have great potential for investigating LD subgroups and metabolic regulations in situ.