ELISA Test 27th July 2022 – Tags:

ELISA Test technology is commonly used in biomedical studies. It helps with diagnostic cases and science causes, where it is still a very popular analytic technology. It is fast, precise and easy to use. It can be automatised. It is also safe and quite cheap.

What is ELISA test for?

ELISA Test (enzyme-linked immunosorbent assay) is an immunoenzymatic test for solid phase. Its role is for the detection and quantification of proteins that are contained in the test sample, such as antibodies or antigens of a protein nature. The method is based on the formation of bonds between the antigen and the antibody, which it makes visible colour reaction, occurring thanks to conjugated with immunoglobulin enzymes and suitable for them substrates.

Procedure:

The tile is covered with a layer of antigen. Later some antibodies, that are specific for the antigen and marked with an correct enzyme are added and we proceed with an incubation . During this time the specific antibodies connect with an antigen, and those that are not connected are being washed out.
The solution substrate/chromophore is added to a tile and the enzyme is catalyzing the reaction. In affect we can spot the colored product . At the end we perform a spectrophotometric measure

ELISA test

What are the types of ELISA tests? What is a Direct ELISA?

There are four types or categories of ELISA tests:

Direct ELISA: binding of an antigen to a polystyrene plate, followed by an antibody labelled with an enzyme that can react with the antigen and a substrate that can be measured.
Indirect ELISA: attachment of an antigen to a polystyrene plate, followed by a primary or unlabelled antibody and then an antibody labelled with an enzyme that can react with both the primary antibody and the substrate.
Sandwich ELISA: a capture antibody is fixed to the polystyrene plate, then an antigen that specifically binds or captures the antigen is added. A second antibody, also specific to the antigen but different from the capture antibody, is added and ‘snares’ the antigen. This second antibody is then followed by an antibody labelled with an enzyme specific for the second antibody that can react with a substrate that can be measured.
Competitive ELISA: this test is similar to the sandwich ELISA, but involves the addition of competing antibodies or proteins when the second antibody is added. This results in a decrease in the signal generated by the substrate. This test gives good and highly specific results.

Advantages and Disadvantages

Advantages

  • High sensitivity and specificity: ELISAs commonly detect antigens at the picogram level with high specificity using antibodies.
  • High throughput: commercial ELISA Test are usually available in 96-well plate format. But the test can easily be adapted to 384-well plates.
  • Ease of execution: protocols are easy to follow and require little handling time.
  • Quantitative: it can determine the concentration of antigen in a sample.
  • It can analyse different types of samples: serum, plasma, cell and tissue extracts, urine and saliva, among others.

Disadvantages

  • Temporary readings: detection is based on enzyme/substrate reactions and therefore the reading must be obtained in a short period of time.
  • Limited antigen information: information limited to the amount or presence of the antigen in the sample.

You can read more in our blog.

References

  1. Research Gate
  2. Biosense