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.