The Sulforhodamine B (SRB) Cytotoxicity Assay, developed in 1990, remains one of the most widely used methods for in vitro cytotoxicity screening. It relies on the ability of SRB to bind to protein components of cells fixed to tissue culture plates. SRB is a bright pink aminoxanthene dye with two sulfonic groups that bind to basic amino acid residues under mild acidic conditions and dissociate under basic conditions. As the binding of SRB is stoichiometric, the amount of dye extracted from stained cells is directly proportional to the cell mass.
The fixed dye is solubilized and is measured photometrically at OD 540 nm with a reference filter of 690 nm. The OD values correlate with total protein content and therefore with cell number.
The assay is sensitive, simple, reproducible and more rapid with better linearity than the formazan-based assays. It has a good signal-to-noise ration and has a stable endpoint that does not require a time-sensitive measurement, as do the MTT or XTT assays.

Content: 0.4 g Sulforhodamine dye, 2x 50 ml Fixative Reagent, 2x 50 ml 10x Dye Wash Solution, 4x 50 ml SRB Solubilization Buffer