VitaBlue is a proprietary fluorometric/colorimetric growth indicator based on detection of metabolic activity of cellls.  It is non-toxic to cells and measures the oxidation-reduction (redox) environment in the medium. Viable cells reduce VitaBlue from its oxidized form (nonfluorescent, blue color) to the reduced form (fluorescent, red color) during cell growth.  The fluorescence intensity of VitaBlue at 540ex/590em is   proportional to the number of viable cells in the sample. If a fluorescence plate reader is unavailable, absorbance difference at 570 nm and 600 nm can be used instead.  Please see graphs below for example.  VitaBlue is suitable for various human/animal and plant cell lines, bacteria, mycobacteria, and fungi.  It can be used to assess cell viability, cell proliferation, and cytotoxicity. It is nontoxic, simple to use, sensitive, stable, and highly reproducible.