– Calcein Orange Diacetate is a fluorogenic dye that is used to assess cell viability. It is hydrolyzed to the fluorescent probe Calcein Orange . Calcein Orange is retained by living cells and displays excitation/emission maxima of 525/550 nm, respectively. Calcein Orange Diacetate is an orange-emitting variant of the green fluorophore Calcein AM , which has been used to evaluate cell viability and cytotoxicity.