Biofunctional structural design of SAW sensor chip surfaces in a microfluidic sensor system

Surface acoustic wave (SAW) sensor chips with a gold or SiO2-polymer surface were integrated into a microfluidic S-sens K5 sensor system to be modified by a novel procedure. Self-assembled composite monolayers were formed on the sensor chip surfaces, starting from special aminocellulose derivatives or from NH2-(organo-) polysiloxanes. Subsequently, the interface layers were biofunctionalized. In one assay, the enzyme glucose oxidase was immobilized on the aminocellulose surface. In a second assay, the formed composite monolayers became thrombin-sensitive by immobilization of an RNA anti-thrombin aptamer. The biofunctionalized surfaces did only display negligible amounts of non-specific protein binding with respect to elastase and bovine serum albumin (BSA). Thrombin was bound highly specific and with high sensitivity. It was possible to regenerate the surfaces under flow conditions.