Question

Explain ELISA
(a) Enzyme-linked inductive assay
(b) Enzyme-linked ion sorbent assay
(c) Enzyme-linked immunosorbent assay
(d) None of the above

Answer 1

Hint: The assay uses a solid-phase type to detect the presence of a ligand (commonly a protein) during a liquid sample using antibodies directed against the protein to be measured.

Complete answer:
The full expression of ELISA is Enzyme-linked immunosorbent assay. It is also known as Enzyme ImmunoAssay, commonly used analytical biochemistry assay. It has become one of the most widely used serological tests for antibody or antigen detection. It was first discovered by Engvall and Perlmann in 1971.
The technique of ELISA:
It is a plate-based assay technique designed for detecting and quantifying soluble substances such as peptides, proteins, antibodies, and hormones.
Principle of ELISA:
- The enzymes that are used as labelled catalysts do a colour change in substrate, which is detected by the spectrophotometry.
- Quantitative estimation of the enzyme reaction shows how much enzyme labelled antigen was bound, which is the inversely proportional to the amount of antigen is the serum or solution being analysed.
Types of the method of ELISA- There are two types of methods:
- Single Antibody/Competitive binding method:the known quantity of enzyme labelled antigen and an unknown quantity of unlabelled antigen is permitted to react with a specific antibody.
- Double Antibody method/Sandwich method: the antigen which is to be analysed is incubated with a specific antibody. Then a second antibody which is labelled with the enzyme is added which binds with an already bound antigen forming an antibody-antigen-antibody complex.
Application of ELISA- It is used in the clinical laboratory to measure
- All hormones in the serum.
- It is used in tumour markers detection.
- Antibodies in the serum are infectious diseases. Eg- antiviral antibodies and antibacterial antibodies.
- It is a helpful aid for controlling serum antibody concentrations.
- It is also useful within the food industry in detecting potential food allergens,
- It is also used in toxicology as a rapid presumptive screen for certain classes of drugs.
So, the correct answer is ‘Enzyme-linked immunosorbent assay’.

Note: ELISA has been used as a diagnostic tool in medicine, plant pathology, and biotechnology, as well as quality control, and check-in various industries. It is a non-isotopic Immunoassay to overcome the disadvantages of using Radioactivity. Enzymes can be attached to the analyte and used in place of radioactive antigen.