Silanized Silica Surfaces Research Articles

34] Surface immobilization techniques in combination with ellipsometry

Publisher Summary The rapid development of bioanalytical methods and biosensors involving immobilized enzymes or antibodies focuses interest on the interaction of biomolecules at inorganic surfaces. It is also of importance to use efficient, gentle, and durable immobilization techniques and that the techniques are suited for large-scale production of sensor devices. The function of several surface-sensitive sensors based on electrochemical, optical, and gravimetric methods requires a proper immobilization of biomolecules to inorganic surfaces. Most such surfaces do not carry suitable chemically reactive groups. Such groups may, however, be introduced by chemical surface modification such as silanization. This process is commonly performed by deposition of the silane from a liquid phase. Several problems, such as nonuniformity of the deposited silane film thickness, codeposition of polymeric silane particles, and hydrolytic removal of the deposited film, occur using this method and are not acceptable for optimum performance of the surface-sensitive measuring devices. Vapor phase silanization can overcome some of these problems. The chemical vapor deposition technique is used for alkoxysilanes. The technique is exemplified by the covalent binding of protein A to silanized silica surfaces and the interaction of the immobilized protein A with immunoglobulins. The result is evaluated by in situ ellipsometry, an optical technique based on reflection of polarized light from a surface.