Carboxyfluorescein diacetate succinimidyl ester (CFDA-SE or CFDA-NHS) is a fluorogenic, cell-permeable esterase substrate tant can be used to detect cell viability. CFDE-SE is a non-fluorescent, amine reactive fluorescein derivative that can pass through cell membrane whereupon intracellular esterase can hydrolyze diacetate group to product a bright carboxyfluorescein product. Resulted fluorescein molecules accumulate in intact cells that can be used as a marker of cell viability. Cells that do not possess an intact cell membrane or an active metabolism may not accumulate the carboxyfluorescein and therefore do not exhibit green fluorescence. Compared to fluorescein diacetate (FDA) or CFDA (carboxyfluorescein acetate) another commonly used cell viability probes, CFDA-SE retains better inside of cells because succinimidyl ester group can react with amine groups. CFDA-SE can also be conjugated to other biomolecules, such as Dextran for cellular transport study.