Competitive Inhibition ELISA (Enzyme-Linked Immunosorbent Assay) is a variant of the traditional ELISA technique designed to measure the concentration of a target antigen in a sample by leveraging the principle of competitive binding. This assay is particularly useful when the target antigen is small or when the antibodies available have high affinity and specificity.
Key Features of Competitive Inhibition ELISA
- Competitive Binding Principle:
- Objective: Measure antigen concentration by competition between sample antigen and a known quantity of labeled antigen for a limited number of antibody binding sites.
- Mechanism: The more antigen present in the sample, the less labeled antigen can bind to the antibody, leading to a decrease in signal.
- High Sensitivity and Specificity:
- Objective: Detect and quantify low levels of antigen with high accuracy.
- Mechanism: Utilize high-affinity antibodies and a competitive format to enhance sensitivity and specificity.
- Quantitative Measurement:
- Objective: Provide precise quantification of antigen concentration in samples.
- Mechanism: Generate a standard curve from known concentrations of antigen to accurately measure antigen levels in test samples.
- Optimized Protocols:
- Procedure: Includes coating, blocking, competition, detection, and measurement steps optimized for reliable and reproducible results.
- Time Efficiency: Designed to deliver results within a few hours, depending on the specific kit and protocol used.
- Reagent Composition:
- Coated Antigen/Antibody: The plate is typically pre-coated with either antigen or antibody.
- Labeled Antigen: Known concentration of antigen labeled with an enzyme or other detectable marker.
- Detection Antibody: Conjugated to an enzyme that will produce a measurable signal.
- Substrate Solution: Reacts with the enzyme to produce a measurable signal (colorimetric, fluorometric, or luminescent).
- Standard Curve Generation:
- Objective: Calibrate the assay for accurate quantification.
- Mechanism: Include known concentrations of labeled antigen in the assay to create a standard curve for determining the concentration of antigen in the samples.
- Sample Types:
- Applicability: Suitable for various sample types, including serum, plasma, cell culture supernatants, and tissue extracts, depending on the kit specifications.
Applications
- Hormone Level Detection: Measure concentrations of hormones, such as cortisol, testosterone, or insulin.
- Toxin Detection: Detect the presence of toxins like mycotoxins, aflatoxins, or pesticides.
- Drug Monitoring: Monitor therapeutic drug levels and drug residues in biological samples.
- Viral Load Measurement: Quantify viral antigens in diagnostic virology.
- Small Molecule Detection: Detect small molecules such as steroids, vitamins, or other metabolites.
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