Surface plasmon resonance antigen-antibody binding

M. Zayats, O.A. Raitman, V.I. Chegel, A.B. Kharitonov, and I. Willner, Probing antigen-antibody binding processes by impedance measurements on ion-sensitive field-effect transistor devices and complementary surface plasmon resonance analyses development of cholera toxin sensors. Anal. Chem. 74, 4763-4773 (2002). 

Very few immunosensors are commercially available. The commercial immunosensors are either the detector or bioanalyzer types. The PZ 106 immunosensor from Universal Sensors Inc. (New Orleans, LA) has been used as a detector to measure antibody-antigen reaction. Ohmicron (Newtown, PA) developed a series of pesticide immuno-bioanalyzers that have been used in field tests. Pharmacia Biosensor USA (Piscataway, NJ) recently introduced BIAcore immunodetection system. A combination of a unique flow injection device and surface plasmon resonance (SPR) detection technique provides a real time analysis. A carboxylmethyldextran layer added to plasmon generating gold film is a hydrophobic, activatable, and flexible polymer that provides high antibody and low non-specific bindings. System demonstration at the Institute of Food Technologists (IFT) 1994 meeting in Atlanta drew attention of food scientists. It should easily be adapted for food protein characterization. 

Surface-plasmon resonance (SPR) has been used to detect surface-bound chemical species. SPR is achieved to detect the binding events of antibody and antigens in immunoassays. A gold-coated PMMA chip that was sealed by a PDMS channel plate was used. The antibodies were first immobilized on the gold layer. Upon binding with benzo[a]pyrene (BaP) 2-hydroxybiphenyl (HBP), the SPR signal was recorded [740]. 

The piezo-electric effect of deformations of quartz under alternating current (at a frequency in the order of 10 MHz) is used by coating the crystal with a selectively binding substance, e. g. an antibody. When exposed to the antigen, an antibody-antigen complex will be formed on the surface and shift the resonance frequency of the crystal proportionally to the mass increment which is, in turn, proportional to the antigen concentration. A similar approach is used with surface acoustic wave detectors [142] or with the surface plasmon resonance technology (BIAcore, Pharmacia). 

The instrument based upon surface plasmon resonance detection (5,9-111 is now routinely used to measure the binding of an antigen (or antibody) to an immobilized antibody (or antigen) in a flow cell. The technology relies on the covalent immobilization of one of the interacting species and the detection of the adsorbed analyte. The sophistication of this expensive instrumentation makes its use difficult for routine investigations in many laboratories. Furthermore, the models used to extract the rate constants are not always appropriate to the kinetic data analysis [ 12-141. 

An antibody is immobilized on the surface of a waveguide (a quartz, glass, or plastic slide, or a gold- or silver-coated prism), and binding of an antigen is measured directly by total internal reflection fluorescence, surface plasmon resonance, or attenuated total reflection. 

---