Fluorescein Diacetate (FDA)

Fluorescein diacetate (FDA) is a cell-permeant esterase substrate that can serve as a viability probe that measures both enzymatic activity, which is require to activate its fluorescence, and cell-membrane integrity, which is required for intracellular retention of their fluorescent product. Upon hydrolysis by intracellular esterases, this AM ester yields fluorescein.