6.2.3 Sulforhodamine B (SRB) assay
In adherent and suspension cell cultures, this assay is a quick and precise colorimetric method for determining drug-induced cytotoxicity. This assay was developed by Skehan and colleagues for the NCI’s large-scale, disease-focused anticancer drug development initiative, which was launched in 1985. SRB is a two-sulfonic-group pink amino xanthene dye. The SRB binds to basic amino acid residues in trichloroaceticacid fixed cells when the environment is slightly acidic, offering a sensitive evaluation of cellular protein. The SRB assay is used to evaluate colony formation and extinction when specific test substances are supplied(Skehan et al., 1990).The SRB test is simple, quick, and accurate to use. It is stationary, independent of intermediate metabolism, has strong cell numbers linearity, saturates dye levels, is less susceptible to environmental variation, requires no time-consuming initial reaction speed measurements, and is less susceptible to environmental fluctuations.(Skehan et al., 1990).This assay has certain limitations in terms of the formation of cell clumps/clusters affecting the homogeneity of the cultures, leading to inappropriate end-point measurements.