ELISA (Enzyme-Linked Immunosorbent Assay) is an immunological diagnostic method used to detect and quantify specific substances, such as antibodies or antigens, in a biological sample. This technique relies on the particular interaction between an antigen and an antibody. It uses an enzyme as a marker to generate a detectable signal (often a color change), which is proportional to the amount of the targeted substance present. ELISA is widely used in the diagnosis of infectious diseases, thanks to its high sensitivity, specificity, and ability to process large numbers of samples simultaneously.
Our expertise in ELISA
At BioSellal, we offer our customers in-depth expertise in the development, optimization, and validation of ELISA kits, to meet today's diagnostic needs. Our ELISA reagents are designed to ensure both sensitive and specific detection of antibodies to pathogens of interest, depending on the animal species. These diagnostic tools are essential for the control of infectious diseases in herds.
All our kits are validated to French standards U47-310 and U47-019 (AFNOR).
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PRACTICAL
Our ELISA reagents are ready-to-use and their components are colored for easy distinction. Our kits are single-pack and with breakable strips.
RAPIDITY
Our incubation protocols are optimized to be as short as possible while guaranteeing reliable results. This enables rapid sample analysis.
RELIABILITY
To ensure the quality of your results, an Internal Reference Material (IRM) is available for each application.
The use of an Internal Reference Material (IRM ) is recommended to improve monitoring and reproducibility of results. IRMs enable test reliability to be checked using a control chart. It is strongly recommended to use them for every test, to guarantee accurate results.
To find out more about our ELISA applications and diagnostic solutions, please contact us.
About ELISA
PRINCIPLE OF INDIRECT ELISA
Indirect ELISA enables the detection and quantification of specific antibodies present in a sample by exploiting the specificity of antigen-antibody interactions and the use of labeled secondary antibodies. The main steps in this technique are as follows:
➜ Immobilization of the antigen: The specific antigen is fixed to the surface of the wells of a microtiter plate. This antigen is the one against which the antibodies to be detected are directed. After immobilization, a wash is performed to remove excess unbound antigens.
➜ Saturation: A saturation solution is added to block non-specific binding sites on the well surface. This step prevents the binding of proteins other than those targeted, thus reducing non-specific reactions.
➜ Incubation with the sample: the sample (often serum, plasma, or milk) containing the antibodies targeting the antigen is added. If specific antibodies are present, they will bind to the immobilized antigen in the wells.
➜ Washing: several wash steps are performed to remove unbound antibodies and other non-specific components from the sample.
➜ Addition of secondary antibody (detection antibody): A secondary antibody, specific to the primary antibody, is added. This antibody is conjugated to an enzyme, such as radish peroxidase (HRP).
➜ Washing: After incubation, wells are washed to remove unbound secondary antibodies.
➜ Substrate reaction: a specific substrate is added and reacts with the enzyme inducing a color change proportional to the amount of primary antibody present in the sample.
➜ Measurement: Optical density (OD) is measured using a plate reader. Signal intensity (color change) is proportional to the amount of specific antibodies in the sample.
PRINCIPLE OFCOMPETITIONELISA
In competition ELISA, the aim is to measure the quantity of specific antibodies in a sample by assessing their ability to interfere with a labeled antibody to bind to a common antigen. This type of test is often used to detect the presence of antibodies in situations where direct detection is less effective.
➜ Antigen immobilization: the target antigen is fixed in the wells of the ELISA plate.
➜ Saturation: A saturation solution is used to minimize non-specific interactions.
➜ Sample addition (first incubation step): The sample containing the specific antibodies (serum, plasma, milk) is added to the wells. The antibodies present in the sample will bind to the immobilized antigen. This incubation allows the antibodies in the sample to start binding to the antigen.
➜ Washing: A wash is performed to remove excess unbound samples and any other substances not specifically bound to the plate surface.
➜ Addition of labeled antibody (second incubation step): After washing, a labeled antibody (enzyme-conjugated, HRP) is added. This antigen-specific labeled antibody will now compete with antibodies in the sample to bind to the immobilized antigen.
➜ Wash: An additional wash is performed to remove excess unbound labeled antibodies.
➜ Detection: A substrate specific for the enzyme bound to the labeled antibody is added. The reaction between enzyme and substrate generates a detectable signal, such as a color change.
➜ Measurement: Signal intensity is measured using a plate reader. A lower signal indicates strong competition, i.e. more specific antibodies in the sample, while a higher signal indicates less competition and therefore fewer specific antibodies in the sample.