The principle of immunoassay sensor operation is based on the observation of ligand-binding reaction products between a target analyte and a highly specific binding reagent. The important component of an immunosensor is the biological recognition element, which normally consists of antibodies or antibody fragments. Immunological methods offer remarkable selectivity and sensitivity through the process of antibody-antigen interaction. As this is the main recognition mechanism by which the immune system detects and fights foreign matter, this technique has permitted the measurement of key compounds at micromolar and even picomolar concentrations in complex biological samples.
An illustration of an immunoassay biosensor is shown below:
The immobilized antibody on the surface of the uncovered portion of the fiber captures the antigen from the sample solution, which is usually introduced into a small flow through a chamber where the fiber tip is located. The sample solution is then removed and a labelled antibody is added into the flow chamber. A fluorescent signal is excited and measured when the labelled antibody binds to the antigen that is already immobilized by the antibody.
Related: The Principle of Surface Plasmon Resonance Sensors for Detection of Antibody & Antigen Interactions
