Several types of tetrazolium salts are used in histological applications, each with unique properties:
1. MTT (3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide): This is perhaps the most commonly used tetrazolium salt in cell viability assays. MTT is reduced by mitochondrial enzymes to form a purple formazan product.
2. XTT (2,3-Bis(2-methoxy-4-nitro-5-sulfophenyl)-2H-tetrazolium-5-carboxanilide): XTT is a water-soluble tetrazolium salt, which produces an orange formazan product. Unlike MTT, the formazan product does not require solubilization.
3. WST (Water-Soluble Tetrazolium Salts): These salts, such as WST-1 and WST-8, produce water-soluble formazan products, making the assays simpler and more convenient. These salts are often preferred for high-throughput screening.
