MTT Tetrazolium Cell Viability Assay

Colorimetric microplate assay measuring cellular metabolic activity and drug cytotoxicity via reduction of yellow MTT to purple formazan.

Specifications & Metrics

type: Cytotoxicity & Cell Viability
readout: Spectrophotometric absorbance of solubilized purple formazan crystals at 500–600 nm
measures: NAD(P)H-dependent cellular oxidoreductase activity, cell viability, proliferation, and cytotoxic IC50
format: 96-well cell culture plates with DMSO or acidified SDS solubilization (or water-soluble MTS/XTT/WST-1 analogs)
pioneer: Tim Mosmann (rapid colorimetric assay for cellular growth and survival, 1983)

Viable, metabolically active cells reduce the yellow tetrazolium salt MTT (3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide) via NAD(P)H-dependent oxidoreductases into water-insoluble purple formazan crystals.
Adding a solubilization solvent (such as dimethyl sulfoxide or acidified sodium dodecyl sulfate) dissolves the purple formazan so a microplate spectrophotometer can quantify optical absorbance between 500 and 600 nm.
Second-generation tetrazolium reagents such as XTT, MTS (paired with phenazine methosulfate), and WST-1 introduce sulfonate groups that yield water-soluble formazan products directly in the culture medium, eliminating the wash and solubilization steps.