Calcein stains (green fluorescence) cells that retain intact membrane structure, but it does not label dead cells and is rapidly lost under conditions that cause cell lyses

Copyright information:Taken from "Alternating current electrical stimulation enhanced chemotherapy: a novel strategy to bypass multidrug resistance in tumor cells"BMC Cancer 2006;6():72-72.Published online 17 Mar 2006PMCID:PMC1435916.Copyright © 2006 Janigro et al; licensee BioMed Central Ltd. Doxorubicin (in red) is normally extruded by drug resistant mechanisms and thus enters untreated cells reluctantly. Note that exposure to either MDR blocker or electrical stimulation achieved a greater uptake of red fluorescent doxorubicin and dramatically decreased the number of viable cells (in green). : In viable cells, hydrolysis of Calcein-AM by intracellular esterases produces fluorescent calcein that is retained in the cell cytoplasm. Exposure to AC stimulation increases doxorubicin cytotoxicity thus compromising cell viability and esterases activity.