Multicolor Lipid Droplet-Targeted Carbonized Polymer Dots with Luminescence Regulation for Bioimaging Applications

Color-tunable, lipid droplet-targeted carbonized polymer dots (CPDs) were fabricated by varying reaction precursors through one-pot solvothermal synthesis. They exhibit gradual luminescence ranging from red to blue via the separation of the reaction products by means of column chromatography. We analyzed the structures of these multicolor CPDs and discovered that their emission wavelengths are regulated by both particle size and surface state. The blueshifts of their emission wavelength from 630 to 500 nm can be attributed to the band gap change, primarily manifested by an increase in N content, a decrease in O content, and a difference in grain size. Multiple photophysical parameters reveal that the synthesized CPDs have excellent luminescent properties. Fluorescence colocalization imaging of our full-color CPDs with lipid droplet-type commercial dyes yielded satisfactory results, displaying no cross-color with commercial dyes. Also, they were feasible for full-color lipid-droplet-targeted in vivo bioimaging of zebrafish, highlighting the lipid-rich yolk sac of zebrafish embryos. In conclusion, these nanoprobes exhibit significant promise in investigating lipid droplet metabolism regulation and offer the benefits of good biocompatibility, ease of fabrication, and lipophilicity.