This section provides overview, applications, and principles of elisa kits. Also, please take a look at the list of 4 elisa kit manufacturers and their company rankings.
An ELISA kit is a type of immunoassay using antibodies for quantification by ELISA.
ELISA is an acronym for Enzyme Linked Immunosolvent Assay, a method for quantifying trace amounts of biological substances using an antigen-antibody reaction. It is sometimes translated as "enzyme immunoassay" or "enzyme-linked immunosorbent assay," but these terms are not commonly used.
ELISA is often used in the field of biology from the viewpoint that trace biological substances can be detected with high accuracy by antigen-antibody reaction. For example, it is used to measure blood proteins such as cytokines, chemokines, and growth factors, or in immuno-oncology to measure soluble immune checkpoint molecules to clarify the status of cancer immunity.
In neurobiology, it is used to quantify Aβ, tau, and α-synuclein proteins that are known to cause neuropathy. Other ELISA kits such as phosphorylation-specific ELISA kits and immunoglobulin ELISA kits are available from our extensive lineup, allowing you to select the ELISA kit that best suits your research and objectives. Competitive type ELISA analysis is also appropriate when measuring histamine, pesticides, dioxin, etc.
ELISA uses an antibody or an antigen that binds specifically to the substance to be measured (antigen-antibody reaction). Finally, an enzyme-labeled antibody (or antigen) is used to detect and evaluate enzyme activity by absorbance measurement.
By measuring the enzyme activity, the concentration of the enzyme in solution, the substances in the reagents involved in the antigen-antibody reaction, and the target substance can be quantified. There are four main methods: direct method, indirect method, sandwich method, and competitive method.
1) Direct method: In this method, the target antigen (or target antibody) is solid-phased on a microplate, and the labeled antigen or antibody directly interacts with it. After the antigen or antibody is applied, the plate is washed and the enzyme activity on the microplate is detected. Since no secondary antibody is required, this method can be performed in a single step and in a short time.
2) Indirect method: First, an antibody specific to the target antigen is applied to the solid-phase microplate. Finally, the enzyme activity of the enzyme on the labeled secondary antibody is detected. This method is characterized by increased sensitivity, but requires more time than the direct method.
1) Sandwich method: A microplate coated with an antibody that binds to the target substance in the sample is used to react with the sample as an antigen. Then, another antibody labeled with an enzyme is reacted with the sample, and the excess antibody is washed off, and the enzyme activity on the microplate is measured. The antigen recognition sites of the solid-phase antibody and the enzyme-labeled antibody must be different. The advantage of the sandwich method is that the specificity of the reaction is higher than that of the direct method, resulting in higher detection accuracy.
2) Competitive method: An antibody that binds to the target substance is coated on a solid phase, and the sample is simultaneously reacted with a labeled antigen of known concentration. If the sample contains a large amount of the target substance, the absorbance decreases because there is little enzyme-labeled antigen that can bind to the antibody. Conversely, if the target substance in the sample is low, the absorbance increases because more of the enzyme-labeled antigen is available to bind to the antibody. Competitive assays can be used to measure small molecules that are difficult to detect using the sandwich method, or when the antibody has only one binding site.
As mentioned above, since detection is based on specific antigen-antibody reactions, it is important, as a prerequisite, to use a product that uses the correct combination of reagents for the sample. In addition, whether using direct, indirect, sandwich, or competitive methods, each method has its advantages and disadvantages, so it is necessary to select the most preferable one according to the purpose of the measurement. Microplates are generally solid-phased by hydrophobic interaction or covalent bonding, but it is important to select the correct microplate according to the binding mode. In addition to hydrophobic and hydrophilic types, many types of microplates are available, including those processed with amino or carboxyl groups for covalent bonding applications.
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