Construction of a Dicyanomethylene-4 H -pyran− N , N ′-Diphenyl-dihydrodibenzo[ a , c ]phenazine Conjugate for the Ratiometric Imaging of Lipid Droplets

The aberrant accumulation of lipid droplets (LDs) is a hallmark of a variety of human diseases including the metabolic dysfunction-associated steatotic liver disease. Here, we constructed a new fluorescent probe (DCM-DPAC-OMe) based on the conjugation between dicyanomethylene-4H-pyran (DCM) and an N,N′-diphenyl-dihydrodibenzo[a,c]phenazine (DPAC) derivative as a single-molecule ratiometric imaging agent for LDs. Interestingly, the introduction of the electron-withdrawing DCM group completely reverses the dual-emission pattern of DPAC. This mechanistic reversal was studied by theoretical and fluorescence-based analyses. The probe was used for the imaging of LDs in live cells exhibiting a ratiometric red-to-blue fluorescence emission shift when dissolved by in situ generated intracellular LDs.