Cell viability and cytotoxicity assays measure cellular or metabolic changes associated with viable or nonviable cells. These assays can detect structural changes such as loss of membrane integrity upon cell death or physiological and biochemical activities indicative of living cells.
The gold standard, and the most sensitive cell viability assay, is the CellTiter-Glo® Luminescent Cell Viability Assay, which measures intracellular ATP. ATP assays quickly lyse the cell, provide ATPase inhibitors and supply luciferase reaction components. Light production is proportional to the number of viable cells.
Promega also offers colorimetric, fluorescence- and bioluminescence-based viability assays based on reducing potential of a viable cell. These include colorimetric (CellTiter 96® AQueous One Solution), fluorescent (CellTiter-Blue® Viability Assay) and bioluminescent (RealTime-Glo® MT Cell Viability Assay) assay options. The RealTime-Glo® MT Cell Viability Assay is a nonlytic assay that s continually monitors cell viability over time based on the reducing potential of the cell.
Cytotoxicity assays measure parameters associated with loss of membrane integrity upon cell death. Cytotoxicity assays may detect cytosolic proteins that should not be released by the cell, unless the cell has lost membrane integrity and the proteins have leaked out of the cell. Lactate dehydrogenase (LDH) release is a well-accepted measure of cell death that can be detected with the bioluminescent LDH-Glo® Assay. The CytoTox-Fluor® Assay uses a fluorogenic peptide substrate to measure "dead-cell protease" activity released from cells that have lost membrane integrity. Alternatively, cytotoxicity assays may detect the ability of cell impermeant dyes to enter cells upon loss of membrane activity. CellTox™ Green is a fluorescent DNA binding dye that binds DNA upon cell death and generates a stable signal that can be measured in real-time cytotoxicity assays.
