- fluorescein is formed by intracellular hydrolysis of CFDA
- carboxyfluorescein contains extra negative charges (structure) and is therefore better retained in cells
- been used in bacteria
- CFDA is moderately permeant to most cell membranes with uptake greater at pH 6.2 than at pH 7.4
- Oregon Green 488 (496/524) carboxylic acid diacetate is a more photostable version and less pH sensitive
- timing issues with how long you have to wait for the compound to be hydrolyzed ?