What is a Sandwich ELISA?

The Sandwich ELISA, the most popular assay choice for many research applications, is unique. Although it also uses two antibodies in conjugation with the target antigen like the Indirect ELISA, one of the antibodies will be used to coat the experimental surface first. After the microplate is thoroughly coated, the target antigen is added to the sample wells and binds to the first antibody. The second antibody is then added to the microplate and binds to the target antigen as well, effectively ‘sandwiching’ the target protein between the two antibodies. This test is highly specific, highly sensitive, and has the advantage of not requiring any form of sample purification, since only the target antigen will be affected by both the antibodies, allowing for excellent experimental readings of analyte concentration. The expense and difficulty of finding suitable paired antibodies is a major detractor, however.