A shear horizontal surface acoustic wave sensor for the detection of antigen–antibody reactions for medical diagnosis

In this paper we describe the development of a shear horizontal surface acoustic wave immunosensor for medical diagnostics. There exists a strong interest in the rapid detection of antigen–antibody reactions at small concentrations in the μg/ml region in plasma, serum, or whole blood. Sensors whose operating principle is based on shear horizontal acoustic surface waves are well suited for this. We have used a spin-on glass film for the guidance of the surface wave as well as for the protection of the aluminum structures of the surface wave transducers from aggressive analyte liquids. This film has proven to considerably enhance the sensitivity of the device, and to simultaneously provide a durable protection of the transducers. Furthermore, polymers based on polyvinylamines have been used for the first time for immobilization of the capture protein. This technique effectively prevents the undesired binding of foreign substances like cells, non-specific antibodies, or other proteins at the sensor surface.