Sulforhodamine B (SRB) Assay Protocol

The Sulforhodamine B (SRB) assay is a colorimetric method used to assess cell viability and measure cellular biomass in biological research and drug discovery. It is commonly employed to determine cell growth inhibition, cytotoxicity, and drug sensitivity.

The SRB assay involves the use of Sulforhodamine B, a red fluorescent dye that binds to cellular proteins under mildly acidic conditions. The dye selectively binds to basic amino acid residues in proteins and forms a stable complex. The amount of dye bound to the proteins is proportional to the total protein content of the cells, which serves as an indirect measure of cell density.

• Seed cells in 96-well microtiter plates at an appropriate density and culture under standard conditions until they reach the desired confluence.
• Treat the cells with experimental compounds or conditions according to the experimental design.
• Remove the culture medium and add 50-100 μL of 10% TCA to fix the cells. Incubate the plates at 4°C for at least 1 hour, or store them at -20°C for later processing.
• After fixation, remove the TCA solution and air-dry the plates. Add 50-100 μL of 0.4% SRB solution to each well. Incubate at room temperature for 30 minutes to allow the dye to bind to cellular proteins.
• After staining, wash the plates with 1% acetic acid to remove unbound dye. Repeat the washing step at least three times to ensure adequate removal of excess dye.
• Allow the plates to air-dry to remove any residual acetic acid.
• Add 100-200 μL of a suitable solubilization solution (e.g., 10 mM Tris base) to each well to solubilize the bound SRB dye.
• After thorough mixing, measure the absorbance of the solubilized dye at an appropriate wavelength (e.g., 540 nm) using a microplate spectrophotometer.
• Calculate the absorbance values and normalize the results as needed based on the experimental design.

Creative Bioarray Relevant Recommendations

• Creative Bioarray provides reliable Sulforhodamine B (SRB) assay for our customers. Additionally, we perform a variety of in vitro toxicity tests and assays. We offer a variety of analysis kits for studying cell cytotoxicity including fluorescent and non-fluorescent reporter dyes.

• Ensure proper fixation of cells with trichloroacetic acid (TCA) to preserve cellular proteins for accurate SRB dye binding. Inadequate fixation can lead to variability in staining intensity and affect the reliability of the assay.
• Maintain consistent staining conditions, including the incubation time and SRB concentration, to ensure uniform binding to cellular proteins. Deviations in staining parameters can lead to non-specific binding and inaccurate results.
• Perform thorough washing steps with acetic acid to remove unbound dye effectively. Inadequate washing can result in background noise and interfere with the accurate measurement of bound SRB dye.
• Be prepared to troubleshoot common issues that may arise during the assay, such as inconsistent staining, variation in absorbance readings, or contamination. Addressing these issues promptly can help maintain the integrity of the data.

SRB Assay