Sequential Injection Flow Immunoassay Based on Surface Plasmon Resonance Sensors

Abstract

Flow immunoassay methods for the determination of several environmental pollutants, such as 2,4-dichlorophenol, bisphenol A, trinitrophenol, pesticides and allergy related compounds, such as histamine and immunoglobulin E (IgE) based on a surface plasmon resonance (SPR) sensor are reviewed from the view point of methodology of immunoassay. In this review, two types of immobilization methods for an antibody or an antigen conjugate for the target molecule on the sensor chip are proposed. One is the immobilization method for the antibody of the target molecule, where the antibody is immobilized on the sensor chip through a gold binding polypeptide and Protein G by taking into account of high orientation of the antibody for an immunoreaction on the sensor chip. The other method is the immobilization of the antigen conjugate in two way, where an antigen conjugate with protein such as bovine serum albumin is immobilized by physical adsorption and an antigen conjugate is immobilized by amino-coupling with an alkane thiol compound, which is preliminary immobilized on the sensor chip as a self-assembled monolayer. In order to enhance the sensitivity of the SPR sensor by increasing the change in the mass on the sensor chip after the immunoreaction, a competitive immunoreactions is adopted for the both immobilization methods, where the antibody or the antigen conjugate is immobilized on the sensor chip. A sandwich immunoassay method for the allergy related compound, IgE, was demonstrated as a sensitive method for enhancement of the SPR sensor signal. In the present flow immunoassay, a sequential injection technique is utilized in order to automate the immunoassay protocol, which consists of many procedures.