MTTassay

The MTT assay is a colorimetric assay used to measure metabolic activity. It relies on the ability of living cells to reduce the tetrazolium salt MTT, (3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide), into a colored formazan product. This reduction occurs in the mitochondria of viable cells through the action of endogenous mitochondrial reductases. The resulting formazan is insoluble in aqueous media and precipitates within the cells.

To quantify the formazan product, cells are typically lysed with a solubilizing agent, such as isopropanol or a detergent solution. This releases the formazan crystals, which are then dissolved. The absorbance of the resulting solution is measured spectrophotometrically at a wavelength of around 570 nm. The intensity of the color is directly proportional to the number of viable, metabolically active cells in the sample.

MTT assays are widely used in various biological research areas, including drug screening, cytotoxicity testing, cell proliferation studies, and analysis of cellular responses to different stimuli. They are relatively simple to perform, cost-effective, and can be adapted for high-throughput screening. However, it's important to note that the MTT assay measures metabolic activity, which can be influenced by factors other than cell number, such as the physiological state of the cells or the presence of certain compounds that interfere with mitochondrial respiration or MTT reduction. Therefore, results from MTT assays are often validated using other cell viability methods.