Live-cell imaging of lipid droplets using solvatochromic coumarin derivatives

Lipid droplets (LDs), the lipid-rich intracellular organelles, serve to regulate many physiological processes and therefore attention has been attracted towards their selective detection. We report positively solvatochromic lipophilic dyes, based on the push-pull framework containing coumarin-pyridine heterocycles for selective live-cell imaging of lipid droplets (LDs) in Cos-7 and McA-RH7777 cells at ultralow concentrations (200 nM). The fluorescent probes show a remarkable increase in fluorescence intensity with time with the hydrophobic core of the lipid droplets contributing to the observed intensity enhancement. The simple structural framework, red emission, strong Stokes shift (>80 nm), and excellent biocompatibility highlight their significance as a versatile imaging tool for studying lipid droplets (LDs).