Analysis of cell viability using time-dependent increase in fluorescence intensity

We report the use of resazurin (AlamarBlue) dye in a robust assay for cell viability of primary cells. Human mononuclear cells were used here for immunological studies, but the method can be applied to monitor reduction potential of any living cell. Reduction of AlamarBlue dye is widely used in several commercial assays of cell viability. Although it is fast and easy with immortal cell lines, the method is impractical for the primary cells due to their slower metabolic activity. We propose that the viability of human primary cells can be determined with AlamarBlue by monitoring the increase in fluorescence intensity in a matter of a few hours. In the presence of AlamarBlue, the dynamic increase in cellular reduction capacity is linear for several hours or, alternatively, the assay can be repeated to monitor the viability at any time point of cell culture. In addition to testing cellular growth rates and cytotoxicity, the application can be used to compare sample quality of cells that have been frozen or represent a pool of multiple donors. This application of the AlamarBlue cell viability assay is simple, rapid, and cost-effective, and therefore it is also well suited for high-throughput studies.