We are continuing our blog with a review of cell death assays for drug discovery. In this posting I will describe cellular metabolism assays to use in your project to measure cell death, cytotoxicity, and proliferation. All assays in our blog are available as a service from Alera Labs. Please contact us at (919) 228-8209 to learn more about our assays services.
Cell Death Assays Measuring ATP or Mitochondrial Metabolism
Quite simply, these assays are based on the assumption that living cells have active mitochondrial metabolism and produce ATP.
Luciferase Assays to measure ATP
Using ATP as a surrogate marker for viability was made possible in high-throughput screening format by luciferase-based assays popularized by Promega Corporation (1):
Figure 1. Firefly Luciferase produces light by promoting reaction between Luciferin and ATP in the presence of oxygen.
Luciferase-ATP reagents are quite costly (at ~$1/assay as of 2011) while also requiring access to expensive (and exotic for many labs) luminometer or scintillation counter. But Luciferase-ATP assays excel where high sensitivity is required. It is possible to assay ATP levels in less than 100 cells and in our hands we saw measurable signal from less than 50 cells. The signal is proportional to the number of cells present. If your cells are truly precious or small numbered, Luciferase assays are a way to go. For example we used this assay for stem cell research projects as well as cell migration project where only a small number of cells migrated across semi-permeable layer.