Cell Viability

Cell viability often corresponds with cell health and the ability of a cell population to survive and function successfully. Measurements for cell viability can be used to correlate cell behavior with the number of viable cells in a population, optimize the growth conditions of cell populations maintained in culture, test toxicology, or assess the efficacy of potential drug candidates. The parameters which define cell viability can be diverse, ranging from the integrity of cell membranes or the activity of intracellular enzymes to the membrane potential of mitochondria or the redox potential of a cell population (Table 1).

Our cell viability indicators and assays are designed to measure the different characteristics of cell viability and produce visual readouts of cell health using a microplate reader, fluorescence microscope or flow cytometer. Individually, each reagent provides a different snapshot of cell health. When combined with complimentary cell-based assays measuring cell proliferation and apoptosis, a more absolute assessment of cell health can be determined.

Methods For Determining Cell Viability

Dye Exclusion Assays

Differentiate live and dead cells using cell-impermeant dyes. Compromised membranes of dead cells permit the influx of cell-impermeant dyes and become stained, whereas viable cells do not. Use trypan blue or other cell-impermeant DNA-binding dyes to determine the number of viable cells in your population.

Dye Reduction Assays

Oxidation-reduction viability indicators are designed to correlate cellular metabolism with the percentage of viable cells in a population. Use chromogenic and fluorogenic indicators, WST-8 and resazurin, to monitor cell metabolic activity. The low cytotoxicity of WST-8 and resazurin are convenient for assays requiring longer incubation.

Fluorescent Esterase Substrates

Cell-permeant esterase substrates determine cell viability by measuring cellular enzyme activity and membrane integrity. Upon diffusion into viable cells, intracellular esterases hydrolyze said substrates into fluorescent compounds that are well-retained within the cell. The  intensity of the signal generated is directly proportional to the number of viable cells and can be monitored with a fluorescence instrument.

Mitochondrial Membrane Potential

Loss of mitochondrial membrane potential (ΔΨm), which is characteristic of the early stages of apoptosis, can be monitored using potentiometric probes to indirectly measure cell viability. These cationic probes readily sequester and stain active mitochondria via the ΔΨm to identify viable cells.

Table 1. Common parameters and methods for assessing cell viability and cytotoxicity

Parameters to monitor Method Examples of Reagents
Cell Membrane Integrity Uses cell-imperment dyes to assess membrane integrity. Dead cells with compromised membranes, easily take up these dyes and become stained
Intracellular Enzyme Activity Uses cell-permeable dyes that are fluorescently activated via intracellular esterase activity in viable cells
Mitochondrial Membrane Potential (ΔΨm) Uses cell-permeable dyes that accumulate in the mitochondria via the ΔΨm to identify viable cells. Loss of ΔΨm is characteristic of apoptosis and dead cells
Cellular Metabolism Monitors cellular metabolic activity using cell-impermeant tetrazolium salts
Monitors the cellular redox potential of entire cell populations
Uses bioluminescent detection to measure ATP and ADP. Changes in the ADP/ATP ratio have been used to differentiate different modes of cell death and viability


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