Cell viability assays measure the relative number of live cells in cell populations, in response to a drug or other perturbation, by involving different experimental techniques depending on the required sensitivity, the throughput, and the model system. Viability assays can be multiplexed with toxicity and cell death assays to provide additional information regarding the relative number of dead cells and type of cell death. We offer assays suited for a broad range of applications that are based on bioluminescent, fluorometric, or colorimetric readouts. Endpoint assays provide sensitive, high-throughput formats, whereas real-time, live-cell assays repeatedly monitor over time and generate multiple data points from a single assay.
The essential cell viability assays are summarised in the table below:
| CellTiter-Glo™ | CellTiter-Fluor | RealTime-Glo™ MT | Calcein AM | XTT | |
| Working principle | Highly sensitive firefly luciferase substrate that reacts with ATP to generate a luminescent signal. | Peptide substrate (Gly-Phe-AFC) enters intact cells, where it is cleaved by the live-cell protease activity to generate a fluorescent signal proportional to the number of living cells. | The assay measures the reducing potential of viable cells, and is ATP-independent, providing an orthogonal method for viability or cytotoxicity determination. | Calcein AM is a lipophilic compound that readily enters cells through the plasma membrane, where it is hydrolyzed by esterases in the cytoplasm to release the polar, green-fluorescent calcein dye. | Reduction of a yellow tetrazolium salt called XTT (2,3-bis(2-methoxy-4-nitro-5-sulfophenyl)-2H-tetrazolium-5-carboxanilide). |
| What is detected | ATP | protease activity | reductases activity | cytoplasmic esterases acitivity | mitochondrial dehydrogenases activity |
| Signal type | luminescence | fluorescence | luminescence | fluorescence | colorimetric |
| Platform | plate reader | plate reader / fluorescence microscopy | plate reader | fluorescence microscopy / flow cytometry | plate reader |
| Sensitivity | 4/4 | 3/4 | 4/4 | 4/4 | 3/4 |
| Throughput | high | high | high | medium | low |
| Is cell lysis required ? | yes | no | no | no | no |
| End-point / real time | end-point | real-time | real-time | end-point | end-point |
| Multiplexing | yes | yes | yes | yes | yes |
| Model system | adherent and suspension cell cultures | ||||
In addition to the above most commonly used assays we also offer alternative approaches to suit specific experimental needs, contact us for more info.
Example output:
