Fluorometric determination of the neutral lipid content of microalgal cells using Nile Red

Abstract The fluorophore Nile Red (9-diethylamino-5 H -benzo[ α ]phenoxazine-5-one) has been used to determine neutral lipid in microalgal cells. Cellular fluorescence of stained cells and gravimetrically or chromatographically determined lipid were linearly correlated when Nile Red was excited at 488 – 525 nm and the fluorescent emision measured at 570 – 600 nm. Nile Red is a vital stain which allowed flow cytometric sorting of live microalgal populations based on their lipid content.