The ELISA was originally conceptualized, independently, in 1971 by Eva Engvall and Peter Perlman3 at Stockholm University in Sweden, and Anton Schuurs and Bauke van Weemen4 in the Netherlands.
They were looking for immunoassays that could detect the presence of antigens or antibodies to replace radioimmunoassays that use potentially harmful radiolabelled antigens or antibodies, so they developed enzyme-based alternatives. There are many companies available that also provide bdnf elisa kit online.
There are now four main types of ELISA, direct, indirect, sandwich and competitive.
Direct ELISA test
In direct ELISA, the antigen or antibody in the sample is non-specifically adsorbed directly onto the test plate. The conjugated detection antibody or target specific antigen is then applied to the well.
Indirect ELISA test
Indirect ELISA or iELISA was originally developed in 19785 for the detection of human serum albumin and works very similarly to direct ELISA except that a secondary antibody step is added. This allows the test signal to be amplified, thereby overcoming the limitations of direct ELISA.
Sandwich ELISA was developed in 1977, as the name suggests, suppresses antigens between antibodies. This technique can use a direct or indirect ELISA format (the ELISA sandwich shown above is based on indirect ELISA), except that instead of binding of non-specific antigen to the test plate, the capture antibody does so in a specific process. This combination further increases the sensitivity and specificity of the analysis.
Competitive ELISA, also known as inhibitory ELISA or blocking ELISA, is perhaps the most complex ELISA technique. The more targets in the attached sample, the lower the analysis output signal. There are many formats that other types of ELISA can adapt to in a competitive format.