The MTT assay, or Methylthiazolyl Diphenyl-Tetrazolium Bromide assay, is a colorimetric technique used to assess cell metabolic activity by measuring the reduction of the yellow tetrazolium salt MTT to insoluble purple formazan crystals by metabolically active cells. The process involves adding MTT solution to cultured cells treated with a test substance, followed by an incubation period allowing viable cells to reduce MTT to formazan. A solubilization solution is then added to dissolve the formazan crystals, and the absorbance is measured using a spectrophotometer at around 570 nm, with the amount of formazan being proportional to the number of viable cells. This assay is widely used in ...