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What Are The Differences Between ELISA Assay Types?

Enzyme-linked immunosorbent assay (ELISA) is a method allowing the quantification of a desired marker in a biological sample. The marker can be an antibody, a hormone, a peptide, or a protein. The quantification of a specific marker using an ELISA-based method can be very advantageous when compared to a more qualitative or semi-quantitative method likes Western blotting.

ELISA is faster, highly sensitive, high-throughput, reproducible and flexible with the ability to analyze a variety of different sample types of diverse origins. There are many companies available that also provide bdnf elisa kit online.

Types Of Elisa:

Direct ELISA Assay

This was the ELISA originally developed by Perlman and Engvall. The surface of the plate is coated directly with the sample. An enzyme-tagged antibody enables its measurement. Incubation is followed by washing, which removes the unbound antibodies from the medium.

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The appropriate substrate is then added to the medium, producing a signal directly proportional to the amount of antigen in the sample.

Indirect ELISA Assay

Indirect ELISA is a two-step binding process involving the use of a primary antibody and a labeled secondary antibody. In this method, the primary antibody is incubated with the antigen-coated wells. Next, a labeled secondary antibody that recognizes the primary antibody is added.

This secondary antibody is often a polyclonal anti-species antibody. A wide variety of labeled secondary antibodies are readily available. A substrate is then added to the well to produce a signal amplification.

Immunometric/Sandwich ELISA Assay

Immunometric assays, also known as sandwich Elisa, use two antibodies specific to the antigen to capture or "sandwich” antigens in the well for detection. Immunometric assays exhibit a direct correlation between antigen concentration and substrate response. Immunometric assays typically employ a capture antibody coated on the plate to bind the antigen of interest.