tetrazoliumreagens

Tetrazolium reagents are a class of organic compounds characterized by a tetrazole ring. They are widely used in biological and chemical applications, particularly as indicators of cellular activity and viability. The most common tetrazolium salts include MTT (3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide), MTS (3-(4,5-dimethylthiazol-2-yl)-5-(3-carboxymethoxyphenyl)-2-(4-sulfophenyl)-2H-tetrazolium), and WST-1 (4-[3-(4-iodophenyl)-2-(4-nitrophenyl)-2H-5-tetrazolio]-1,3-benzenedisulfonate).

The principle behind their use relies on their ability to be reduced by metabolically active cells. In living cells, enzymes such as mitochondrial dehydrogenases can reduce the soluble tetrazolium salt into a formazan product. This formazan is typically a colored precipitate that is insoluble in aqueous media, although some modern tetrazolium reagents like MTS and WST-1 produce soluble formazan products, simplifying subsequent measurement. The amount of formazan produced is directly proportional to the metabolic activity of the cells.

This reduction process allows tetrazolium reagents to serve as a sensitive assay for cell proliferation, cytotoxicity, and enzyme activity. For instance, in the MTT assay, the formazan product is dissolved in an organic solvent, and the absorbance of the solution is measured spectrophotometrically. Higher absorbance indicates greater metabolic activity and cell viability. These assays are commonly employed in drug discovery, toxicology studies, and basic research to assess the effects of various compounds or conditions on cells.