31/03/2021
ELISA (enzyme-linked immunosorbent assay) is a plate-based assay technique designed for detecting and quantifying soluble substances such as peptides, proteins, antibodies, and hormones. Other names, such as enzyme immunoassay (EIA), are also used to describe the same technology.
1. A direct ELISA (enzyme-linked immunosorbent assay) is a plate-based immunosorbent assay intended for the detection and quantification of a specific analyte (e.g. antigens, antibodies, proteins, hormones, peptides, etc.) from within a complex biological sample.
2. Indirect ELISA is a two-step ELISA which involves two binding process of primary antibody and labeled secondary antibody. The primary antibody is incubated with the antigen followed by the incubation with the secondary antibody.
3. A sandwich ELISA measures antigen between two layers of antibodies (capture and detection antibody). The target antigen must contain at least two antigenic sites capable of binding to antibodies. Monoclonal or polyclonal antibodies can be used as the capture and detection antibodies in sandwich ELISA systems.
4. The central event of competitive ELISA is a competitive binding process executed by original antigen (sample antigen) and add-in antigen. The procedures of competitive ELISA are different in some respects compared with Indirect ELISA, Sandwich ELISA and Direct ELISA.