ELISA

Enzyme-linked immunosorbent assay, or ELISA, is a technique used to detect the presence or quantity of a specific protein or molecule, usually an antigen or antibody, in a sample. It relies on the specificity of antibody-antigen interactions.

How it works:

In a basic ELISA setup, a known antibody is attached to a surface (such as a microplate well). The sample is added, and if the target molecule is present, it binds to the antibody. A secondary antibody, linked to an enzyme, is then added. This antibody binds to the target molecule. When a substrate is introduced, the enzyme catalyzes a reaction that produces a detectable signal—usually a color change.

Applications:

• Detecting pathogens or antibodies (e.g., HIV tests, COVID-19 serology)

• Measuring hormone levels (e.g., hCG - the hormone tested for in pregnancy tests)

• Monitoring immune responses in research

• Quantifying protein expression in samples

How to interpret data:

Results are measured by the intensity of the color change. Sometimes - like with a pregnancy test, it's done as simply as whether there is a change or not. However, for more detailed data collection and experiments, this is typically using a spectrophotometer. Stronger color corresponds to higher concentrations of the target molecule.