The measurement of cell proliferation and cell viability has become a key technology in the life sciences. The need for sensitive, reliable, fast and easy methods has led to the development of several standard assays. These include the determination of DNA synthesis by measuring the amount of radioactive labeled nucleosides like [3H]-thymidine incorporated in nucleic acid. Alternatively, the incorporation of 5-bromo-2’-deoxyuridine (BrdU) in place of thymidine is used to monitor DNA synthesis and cell proliferation in immunohisto- and immunocytochemistry, in cell ELISA and flow cytometry analysis. Proliferation assays have become available for analyzing the number of viable cells by the cleavage of tetrazolium salts added to the culture medium.

This technique requires neither washing nor harvesting of cells and the complete assay from the onset of the microculture to data analysis by ELISA reader is performed in the same microplate. The microtiter tetrazolium assay allows rapid, convenient and automated handling of high number of samples and is thus a viable alternative to the following methods. The Cell Proliferation Reagent WST-1 is a clear, slightly red, ready-to-use solution, containing WST-1 and an electron coupling reagent, diluted in phosphate buffered saline, sterile filtered.