Cytotoxicity Assay:

 
          The CytoTox 96 Non-Radioactive Cytotoxicity Assay is a colorimetric non-radioactive cytotoxicity assay. It quantitatively measures lactate dehydrogenase (LDH), a stable cytosolic enzyme that is released upon cell lysis. Released LDH in culture supernatants is measured with a 30 to 60 minute coupled enzymatic assay that results in the conversion of a tetrazolium salt into a red formazan product. The amount of color formed is proportional to the number of lysed (dead) cells. Visible wavelength absorbance data is collected using a standard 96-well plate reader. Thus, the assay can be used to determine the total number of viable cells in a given sample.
          The modified MTT assay works similarly, but uses LDH to determine cell viability rather than cell death.