XTT colorimetric assay
XTT colorimetric assay
The XTT colorimetric assay is a widely used quantitative technique that evaluates cell metabolic activity based on a color change resulting from XTT reduction. Specifically, the assay relies on the conversion of the yellow tetrazolium salt XTT into an orange-colored formazan product, a reaction catalyzed by mitochondrial oxidoreductase enzymes present only in metabolically active, living cells. This reaction requires the presence of electron coupling reagents that facilitate electron transfer during cellular respiration. The resulting soluble orange formazan dye is measured spectrophotometrically, typically at 450 nm, with the absorbance directly proportional to the number of viable cells.
TribioScience’s XTT Cell Viability Assay Kit offers a straightforward and high-throughput solution for assessing cell viability and proliferation without requiring additional reagents or washing steps. The solubility of the formazan dye in culture media simplifies the workflow, eliminating the need for cell lysis or extraction. The assay is highly accurate, as the absorbance measured correlates linearly with the number of viable cells in each well. Researchers frequently use this assay to monitor cellular responses to growth factors, cytokines, mitogens, or nutrient availability. It is also commonly applied in drug screening to evaluate the cytotoxic or proliferative effects of pharmaceutical agents, including anticancer compounds.
The assay procedure involves culturing cells in a 96-well plate, preparing and adding the XTT working solution, and incubating the plate to allow dye development. Typically, cells ranging from 1,000 to 10,000 per well are treated with 50 µL of the working solution—a 1:50 mix of XTT reagent and activator—and incubated for 2–4 hours at 37°C. After incubation, the absorbance is measured at 450 nm using a plate reader, providing quantitative data on cell viability. The method’s non-radioactive nature, minimal handling steps, and adaptability to various experimental designs make it an indispensable tool in both basic research and pharmaceutical testing.
