Fluorescein dicaprylate [Fluorescein dioctanoate]

Fluorescein dicaprylate is a non-fluorescent hydrophobic fluorescein derivative that can pass through the cell membrane whereupon intracellular esterases hydrolyze the dicaprylate group producing the highly fluorescent product fluorescein. The fluorescein molecules accumulate in cells that possess intact membranes so the green fluorescence 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 fluorescent product and therefore do not exhibit green fluorescence. Fluorescein dicaprylate may be used in combination with PI staining as the non-viable cells take up the PI and stain dead cells red whereas viable cells do not take up the PI and should only stain green. Fluorescein dicaprylate may stain Samonella in green fluorescence.