6.4.1 Adenosine triphosphate (ATP) assay
A major chemical energy storage system in cells, ATP is used for biological production, signalling, transport, and movement. Consequently, one of the most accurate biomarkers of cell viability is cellular ATP(Maehara et al., 1987). As a result of being unable to synthesise ATP, cells’ levels of ATP drop if the integrity of their membranes is compromised. Luciferin activation into oxyluciferin serves as the foundation for the ATP assay. The bright signal is produced as a result of the activity being catalysed by the enzyme luciferase in the presence of Mg2+ ions and ATP. The strength of the bright signal depends on ATP levels.(Mueller et al., 2004) or the number of cells. The ATP test chemical is often used in the 1536-well plate format since it can detect fewer than 10 cells per well(Andreotti et al., 1995).
The ATP assay is the quickest, most sensitive, and least artifact-prone viability assay available. The luminous signal stabilises and reaches a steady state after 10 minutes of reagent addition. There is no need for an incubation stage because the substrate is transformed into a colourful compound. Additionally, handling plates is avoided. Instead of the test’s chemistry, the sensitivity of the ATP assay is typically constrained by the reproducibility of pipetting duplicate samples(Riss et al., 2004).