The use of dextran as an intermediate layer: a new approach towards SAW based biosensors

We present a new method for covalent binding of dextran as an intermediate layer on surface acoustic wave (SAW) devices. The SAW devices were originally developed for use in modern telecommunications and are thus available as series products at low costs. For biosensing applications these devices must be coated with a shielding layer to prevent corrosion effects of the aluminium structures in aqueous media. Thin films of polyimide and parylene, respectively showed good shielding properties and were used as a base for further immobilization. Dextran immobilization to the polymer coated surfaces is achieved by a photoimmobilization process. A aryldiazirine-functionalized protein (T-BSA) serves as a multifunctional light-activated linking agent (photolinker polymer). Dextran and the photolinker are mixed and photobonded to the sensor surface. Immobilization of proteins to the dextran layer via carbodiimide chemistry is demonstrated with anti-urease antibodies and the feasibility of specific immunosensing is investigated using SAW sensors connected to a fluid handling system.