Cell Counting Kit-8 (CCK-8) allows very convenient assays by utilizing Dojindo's highly water-soluble tetrazolium salt. WST-8 [2-(2-methoxy-4-nitrophenyl)-3-(4-nitrophenyl)-5-(2,4-disulfophenyl)-2H-tetrazolium, monosodium salt] produces a water-soluble formazan dye upon reduction in the presence of an electron mediator.

Cell Counting Kit-8 is a one-bottle solution; no premixing of components is required. Cell Counting Kit- 8, being nonradioactive, allows sensitive colorimetric assays for the determination of the number of viable cells in cell proliferation and cytotoxicity assays. WST-8 is reduced by dehydrogenases in cells to give a yellow-colored product(formazan), which is soluble in the tissue culture medium. The amount of the formazan dye generated by the activity of dehydrogenases in cells is directly proportional to the number of living cells. The detection sensitivity of CCK-8 is higher than other tetrazolium salts such as MTT, XTT, MTS or WST-1.

• One solution only
• Easy to manipulate, only 3 steps 
• No need to re-dissolve tetrazolium salt
• More sensitive than MTT, MTS, or WST-1
• No toxicity to cell

Product Introduction link:
http://www.cyrusbio.com.tw/webc/html/news/show.php?num=59&kind=1&page=1