ELISA Methodology & Research Applications

The Principle of Sandwich ELISA Methodology

Sandwich ELISA is the most widely used format for quantifying proteins such as cytokines, acute phase proteins, hormones and immunoglobulins in biological samples. The method relies on two antibodies that each recognize a distinct epitope on the same target analyte, allowing the analyte to be "sandwiched" between a surface-bound capture antibody and a labeled detection antibody.

In general terms, a microplate is first coated with a capture antibody specific to the analyte of interest. Samples, standards and controls are then added to the wells, and if the target analyte is present, it binds to the immobilized capture antibody during an incubation step. Unbound material is removed by washing, after which a detection antibody conjugated to an enzyme, or paired with an enzyme-linked secondary antibody, is introduced. This detection antibody binds to a separate epitope on the captured analyte, forming the characteristic sandwich complex.

Following a further wash step to remove unbound detection reagents, a chromogenic or similar substrate is added. The enzyme bound within each complex converts this substrate into a measurable signal, most commonly a color change that is proportional to the amount of captured analyte. A stop solution is typically used to halt the enzymatic reaction at a defined time point, and the resulting signal is read on a plate reader. Analyte concentrations in unknown samples are then interpolated from a standard curve generated using reference standards of known concentration run in parallel.

This general principle underlies the broad family of ELISA kits in this catalog, regardless of species or biomarker class, and provides the basis for the sample-to-result workflow and application mapping described below.