DEVELOPMENT AND CHARACTERIZATION OF SURFA CE-PLASMON RESONANCE (SPR)-BASED IMMUNOSENSOR

Realtime and nonlabelled sensing based on antigen-antibody reaction ha s been investigated by a surface plasmon resonance (SPR)-based optical biosensor. The sensor detects the change in the refractive index of t he metal film surface upon injection of antigen/antibody. in this pape r the characteristics of the sensor in immobilized format of antigen ( antibody) on gold surface are described; immobilization of antigen/ant ibody on gold surface was performed either by physical adsorption or b y covalent immobilization to an organic film in the monolayer and poly er film. Although the former method was simpler, however, constant res ponse was not obtained in repetitive antigen/antibody bindings. For th e detection of antigen/antibody by the SPR sensor with a sensitivity t hat cannot be easily attained in other methods, it is desired to immob ilize antigen/antibody as much as possible in a polymer matrix having low refractive index. Covalent binding of oxidized hydroxyethylstarch polymer was performed onto thin gold film surface via self-assembled m onolayer of aminoethanethiol. The immobilized starch layer was reduced by sodium borohydride after antigen/antibody immobilization, because Schiff's base is not necessarily stable through the repeated associati on-dissociation by an acidic buffer, glycine-HCl (pH 2.5). By the NaBH 4 treatment of sensing layer the repeated detection of the determinant was carried out at least 20 times.