- An ATP assay is a biochemical method used to measure the amount of adenosine triphosphate (ATP) in biological samples.
- ATP is the universal energy currency of cells, and its concentration directly reflects cellular metabolic activity and viability. Because of this, ATP assays are widely used in cell biology, microbiology, pharmacology, and toxicology to assess cell proliferation, cytotoxicity, apoptosis, and overall bioenergetic status.
- The principle of most ATP assays relies on the luciferase-luciferin bioluminescence reaction. In this system, the enzyme firefly luciferase catalyzes the oxidation of luciferin in the presence of ATP, magnesium ions, and oxygen, producing light. The intensity of the emitted light is directly proportional to the ATP concentration, and thus to the number of metabolically active cells. This makes the assay highly sensitive, often capable of detecting even a few cells in a sample.
- ATP assays can be applied in several contexts. In cell culture experiments, they are used to monitor cell proliferation, screen for drug toxicity, or evaluate anti-cancer compounds. In microbiology, ATP assays serve as rapid methods to detect bacterial contamination or monitor sterilization efficiency. In food and environmental testing, ATP measurement is used as a hygiene indicator, since the presence of ATP signals microbial or organic contamination.
- There are different formats of ATP assays, including endpoint assays (where luminescence is measured after cell lysis and reagent addition) and real-time assays (which allow continuous monitoring of ATP dynamics in living cells). Commercial kits often combine cell lysis, ATP stabilization, and luminescence detection in a simple protocol. While highly sensitive and convenient, ATP assays do have limitations: ATP levels can fluctuate rapidly depending on cell type, metabolic state, and external conditions, so results should be interpreted carefully, often in combination with other viability or cytotoxicity assays.
