ELISA (Enzyme-Linked Immunosorbent Assay) is a widely used laboratory technique for detecting and quantifying specific molecules such as proteins, antigens, antibodies, or hormones in a sample. Known for its high sensitivity and specificity, this method relies on the interaction between an antigen and an antibody, coupled with an enzyme that generates a measurable signal, often in the form of colour or fluorescence.
Principle of the ELISA Method:
- Antigen or Antibody Immobilization: ELISA begins with the immobilization of the target antigen (or antibody) onto a solid surface, typically a polystyrene microtiter plate.
- Sample Addition: The sample to be analysed, containing the target antigen or antibody, is added to the plate. If the sample contains the target molecule, it will bind to the immobilized antibody or antigen.
- Enzyme-Labelled Antibody: A specific antibody, conjugated to an enzyme, is added. This binds to the antigen-antibody complex, forming a sandwich-like structure.
- Enzymatic Reaction: After washing to remove unbound components, a specific substrate for the enzyme is added. The enzyme reacts with this substrate, producing a measurable signal (usually a colour change).
- Result Reading: The intensity of the signal (colour, fluorescence, or luminescence) is proportional to the amount of the target molecule in the sample. This is often measured using a spectrophotometer or a plate reader.
Advantages of the ELISA Method:
- High Sensitivity: ELISA can detect very low concentrations of molecules in a sample.
- Specificity: The method is highly selective for the target molecule due to the use of specific antibodies.
- Accurate Quantification: The enzymatic signal is proportional to the analyte concentration, enabling precise quantification.
- Ease of Use: ELISA is a relatively simple technique that can be adapted for high-throughput analysis.
ELISA thus is an essential technique in clinical laboratories, research, and industry, known for its ability to provide reliable, reproducible, and sensitive results. Its flexibility and wide range of applications make it a key tool for the detection and quantification of biomolecules across various fields.