Short Notes
(i) ELISA – Enzyme-Linked Immunosorbent Assay
ELISA is a widely used biochemical technique to detect and quantify substances such as hormones, proteins, peptides, or antibodies in biological samples.
Principle:
- ELISA uses the principle of antigen-antibody binding.
- An enzyme is linked to an antibody. When a specific substrate is added, the enzyme produces a color change indicating the presence of the target molecule.
Types of ELISA:
- Direct ELISA
- Indirect ELISA
- Sandwich ELISA
- Competitive ELISA
Applications:
- Hormone level measurement (e.g., insulin, hCG)
- Detection of infectious diseases like HIV, COVID-19
- Food safety and allergy testing
(ii) RIA – Radioimmunoassay
RIA is a sensitive laboratory technique used to measure minute concentrations of hormones or other biological molecules in blood.
Principle:
- Involves competition between radioactively labeled and unlabeled antigen for binding to a specific antibody.
- The bound and free antigens are separated, and the radioactivity is measured using a gamma counter.
Applications:
- Measurement of hormone levels like insulin, cortisol, T3, T4, and TSH
- Drug testing and pharmacokinetics
- Diagnosis of endocrine disorders
Advantages:
- Extremely sensitive – can detect picogram levels
- Highly specific due to antibody-antigen interaction
Conclusion
Both ELISA and RIA are powerful techniques in medical diagnostics and research. While ELISA is safer and easier due to non-radioactive labeling, RIA remains the gold standard for detecting very small amounts of hormones and drugs.