Cytotoxicity Test

Cell cytotoxicity is a simple cell killing event caused by cells or chemicals and does not depend on the apoptotic or necrotic mechanism of cell death.Sometimes cytotoxicity testing is required for specific substances, such as drug screening.

Normal cells are metabolically vigorous and their mitochondria contain succinate dehydrogenase, which can reduce tetrazolium salts (e.g., MTT, XTT, WST-1, and WST-8, etc.) to purple crystalline substances that deposit around the cell. Then we can use a microplate reader to read the OD value (optical density), thus detecting the status of cell proliferation.

Cell counting kit-8 (also known as CCK-8) is a rapid and highly sensitive assay based on WST-8 (Water Soluble Tetrazolium-8) and widely used for cell cytotoxicity analysis.

The rationale is: WST-8 [chemical name: 2-(2-Methoxy-4-nitrophenyl)-3-(4-nitrophenyl)-5-(2,4-disulfophenyl)-2H-tetrazolium Sodium Salt] is reduced by dehydrogenases in cells under the reaction of the electron carrier 1-methoxy-5-methylphenazinium sulfate dimethyl ester (1-methoxy PMS) to a highly water-soluble yellow formazan product (formazan dye).The number of formazans generated directly correlates to the number of living cells.This property can therefore be exploited to directly carry out cell cytotoxicity assays.The more rapidly the cells proliferate and the more cells proliferate, the darker the color is, and the more toxic the cells are, the lighter the color is.For the same cells, there is a linear relationship between the intensity of the color and the number of cells.