WST-8

WST-8 is a water-soluble tetrazolium salt commonly used in colorimetric assays to measure cell viability and enzyme activity. Upon reduction, primarily by mitochondrial dehydrogenases in viable cells, it produces a yellow-orange formazan dye, which can be quantitatively measured via absorbance, reflecting the metabolic activity of the cells.

To enhance electron transfer and boost sensitivity, 1-methoxy-5-methylphenazinium methyl sulfate (1-methoxy PMS or mPMS) is employed as an intermediate electron carrier. This combination forms the foundation of the WST-8/mPMS assay, a widely used method due to its simplicity, high sensitivity, and non-radioactive nature.

The WST-8/mPMS system is advantageous over traditional MTT assays because WST-8’s formazan product is water-soluble, eliminating the need for organic solvents in solubilization steps.

Cell Viability and Cytotoxicity Assays: Used extensively in drug screening, toxicology, and cancer biology to determine cell proliferation or cytotoxic effects. The pairing with mPMS ensures better electron transfer and reduces variability across assay formats.

Dehydrogenase Enzyme Assays: The WST-8/mPMS system efficiently monitors NAD(P)H production, making it ideal for studying enzymes such as lactate dehydrogenase and other oxidoreductases.

Microbial Viability: Rapid detection of live microorganisms through metabolic activity was demonstrated using the WST-8-mPMS assay in biosensing platforms.

Comparative Studies with Other Tetrazolium Salts: Studies have shown that WST-8, when paired with mPMS, outperforms or complements other tetrazolium-based systems (e.g., MTT, XTT) in terms of accuracy and biocompatibility in 2D and 3D cultures.