Tetramic Acid-Derived Blue-Emitting Fluorescent Probe for Selective Lipid Droplet Imaging in Live Cells and Zebrafish

Lipid droplets (LDs) are dynamic intracellular organelles involved in lipid storage and metabolism, and their imaging is essential for studying metabolic processes in health and disease. Here, we describe four novel fluorescent tetramic acid derivatives as potential LD markers for live imaging in cellular and whole-organism systems, and designate the compound with the most favorable properties, 1a, for further characterization. The probe 1a was evaluated in multiple cell lines, where it enabled clear visualization of intracellular LDs and showed strong colocalization with established lipid markers such as Nile Red and BODIPY 493/503. Photophysical characterization revealed photostability and signal-to-noise characteristics enabling fluorescence imaging applications. In addition, cytotoxicity assays indicated minimal acute and delayed effects at imaging concentrations. Importantly, 1a was successfully applied in a zebrafish model, enabling visualization of lipid-rich structures in a whole-organism context. Together, these findings identify 1a as a useful LD fluorescent marker for live imaging applications both in vitro and in vivo.