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Enzyme-linked immunosorbent assay (ELISA) is an in-vitro laboratory technique through which target proteins and molecules can be detected in biological samples. This technique has similarities to other immunoassays which rely on specific antibody binding to detect a protein or target of interest. This detection consists of specific antigen-antibody interactions to quantify or qualify the presence of the target.

In our store, you will find over 4,500 ELISA kits which target proteins and compounds across major research areas. ELISA kits are available for you to target proteins found in common animal models like human, mouse and rat, among others. Quantify or qualify your detection with the use of sandwich or competitive kits in under 4 hours.

Our ELISA kits have been strictly quality-tested to ensure the accuracy of results.

Direct ELISA

This type of ELISA assay is significantly faster than the rest and has less steps.

There is no signal amplification with direct ELISA, due to the lack of secondary antibody, leading to less sensitive assay, making this technique better suited for analysing the immune response to an antigen.

A major drawback of direct ELISA is the possibility of higher background noise due to non-specific antigen immobilization, caused by all the proteins alongside the target one binding to the plate.

Indirect ELISA

Being cheaper and more sensitive than direct ELISA, the indirect technique can offer splendid flexibility.

This type of assay is more time-consuming and utilises a two-step detection process, using a primary antibody for target binding and a labelled secondary one, raised against the host species of the primary one, for detection.

The biggest advantage of this method is that it allows for a wide variety of primary antibodies to be used with a single labelled secondary antibody, making indirect ELISA a great choice for determining the total antibody concentration in a sample.

Sandwich ELISA

Sandwich immunoassays are the most common type of ELISA.

This type of assay utilizes a matching antibody pair, one antibody for capturing and the other for antigen detection, making it between two and five times more sensitive than the two previous types of ELISA. Each of the antibodies in the matching pair is raised to be specific for different and non-overlapping epitopes of the same antigen and needs to be tested in a sandwich assay so this quality can be validated and accurate results achieved.

With two antibodies participating in capture and detection, the specificity is also higher and sandwich ELISA can use both direct and indirect detection, resulting in greater flexibility.

The sandwich immunoassay can be of two types, depending on the detection antibody. If it is enzyme-conjugated, the assay is referred to as direct sandwich ELISA, but if the detection antibody is unlabelled, the assay requires a secondary enzyme-conjugated antibody to be used, making it an indirect sandwich ELISA. This type of assay is most often used for analysing complex samples because it doesn't need the antigen to be purified prior to the experiment.

Competitive ELISA

Also known as blocking ELISA, this technique is the most complex of all the previous and is generally used for measuring the concentration of an antigen via interference detection in signal output. It is less sensitive to sample dilution and matrix effects when compared to sandwich ELISA and out of all the variations, competitive ELISA offers the best flexibility.

In a competition ELISA, the sample antigen has to compete with a reference standard in order to bind to a limited amount of antibodies. This process is largely dependent on the concentration of the sample, which inversely correlates to the strength of the signal output. The higher the sample concentration, the weaker the signal output is.

Inhibition ELISA is more robust when compared to the sandwich variation of the assay and offers better consistency between duplicate samples, as it doesn't require any sample processing and allows for impure or crude samples to be used. Furthermore, this assay is best suited for the detection of small antigens, which cannot be bound by two different antibodies, as is the case with sandwich ELISA