The most commonly used solid-phase carrier in ELISA is the microplate made of polystyrene. Its adsorption of proteins forms the basis of the entire detection system, and the core principle behind this lies in the non-covalent interactions between the surface of the solid-phase material and protein molecules.
Coating is the process of immobilizing specific antibodies or antigens on the surface of a solid-phase carrier. Its quality directly affects the sensitivity, specificity, and reproducibility of the experiment. It is equivalent to building an "exclusive reaction platform" for subsequent antigen-antibody reactions.
There are different opinions on the detection and classification of ELISA, and different literatures have different classification opinions in terms of principle or operation. Here we divide ELISA into the following four categories, and then explain each category in detail: (1) direct ELISA; (2) indirect ELISA; (3) Sandwich ELISA; (4) Competition inhibits ELISA. Other ELISA are affiliated with, or derived from, a combination of these four types of ELISA.
Enzyme-labeled antibody technology is a labeling technique that involves covalently conjugating enzyme molecules to specific antibodies. Its core principle is: utilizing the antibody's high specificity for antigen recognition as a "targeting system" to precisely locate the target molecule; then, leveraging the enzyme's highly efficient catalytic "amplification effect" on its substrate to convert an invisible immune reaction into a visible or instrument-detectable signal (such as a color change, luminescence, etc.). This enables the qualitative, locational, or quantitative analysis of the target antigen or antibody.
High background No signal Too much signal - whole plate turned uniformly blue Standard curve achieved but poor discrimination between points Poor duplicates Poor assay to assay reproducibility No signal when a signal is expected, but standard curve looks fine Samples are reading too high, but standard curve looks fine Very Low Readings Across the Plate Green color develops upon addition of stop solution when using streptavidin-HRP Edge Effects
Depending on the detection purpose, common types of ELISA include the indirect method (for measuring antibodies), the double antibody sandwich method (for measuring antigens), and competitive methods. Among these, the double antibody sandwich method and the indirect method are the most widely used. The following example will detail the standard operating procedures and key considerations for the double antibody sandwich method.
The ELISA sample collection and storage conditions listed below are intended as general guidelines. Specific protocols may vary by cell line or tissue type. If storing sample for extended length of time, testing sample stability is recommended. Avoid repeated freeze-thaw cycles for all sample types.
These three techniques(RIA,ELISA,Westernblot) are fundamental immunoassay techniques in biomedicine, used to detect specific biomolecules (such as proteins, hormones, antibodies). Their core differences lie in their detection principle, target molecule, sensitivity, specificity, throughput, and application.
ELISA, which stands for Enzyme-Linked Immunosorbent Assay, is a foundational technique in biomedical research and diagnostics. Its core principle leverages the highly specific binding reaction between an antigen and its antibody, amplifying and visualizing this interaction through an enzymatic colorimetric reaction. This allows for the qualitative or quantitative detection of extremely trace amounts of a target substance (antigen or antibody).
