6.2 Colorimetric assays
To measure cell metabolic activity, colorimetric tests rely on the detection of a biochemical marker. A spectrophotometer can be used to measure colorimetric cell viability because colorimetric test reagents alter colour in response to cell viability. Colorimetric tests are straight forward to conduct and reasonably priced. They can be used with adherent or suspension cultures(Berg et al., 1994). The majority of experimental protocols for these assays are included in the kit packages for colorimetric test kits, which are offered by a variety of vendors.