Evaluation of MTT and Trypan Blue assays for radiation-induced cell viability test in HepG2 cells

Background: Cell viability is an important factor in radiaon therapy and thus is a method to quanfy the effect of the therapy. Materials and Methods: The viability of human hepatoma (HepG2) cells exposed to radiaon was evaluated by both the MTT and Trypan blue assays. The cells were seeded on 96 well-plates at a density of 1 x 104 cells/well, incubated overnight, and irradiated with 1-100 Gy. Results: The cell viability was decreased in a dose- and me- dependent manner when using the Trypan blue assay, but no significant changes in the response to dose could be detected using the MTT assay. It indicated that the MTT assay was not efficient at a cell density of 1 x 104 cells/well on 96 well-plates to determine cell viability. Subsequently, the relaonship between cell viability and lower cell density (1 x 103, 3 x 103, and 5 x 103 cells/well) was invesgated. A cell density of 1 x 103 was found to be the most effecve when using the MTT assay. Results show that the cell density is most important when using the MTT assay in 96 well-plates to follow in radiaon effects. Furthermore, the radiaon-induced cell viability dependent on cell density was confirmed by using the tradional Clonogenic assay. Conclusion: Our results suggest that the MTT and Trypan blue assays are rapid methods to detect radiaon-induced cell viability of HepG2 cells in about 3 days as compared with 14 days of assay me in the Clonogenic assay. To obtain accurate cell viability measures using both rapid assays, an incubaon me of at least 3 days is needed a6er irradiaon.