A streptavidin surface on planar glass substrates for the detection of biomolecular interaction

Based on the requirements of biomolecular interaction analysis on direct op tical transducers, a streptavidin surface is examined. A general protocol w as developed allowing the immobilization of biotinylated compounds using th e rife biotin-streptavidin system. This type of surface modification can be applied to all biosensors using glass surfaces as sensor devices. Reflecto metric interference spectroscopy (RIfS), a label-free, direct optical metho d was used to demonstrate the quality of the transducer sill-faces. The sur face modification is based on an aminofunctionalized polyethylene glycol la yer covalently bound to the silica surface of the transducer and shows very little nonspecific binding. Biotin molecules can be easily coupled on such layers. Streptavidin followed by a biotinylated estrone derivative was imm obilized by incubation of the biotinylated transducer surface. For the stre ptavidin layer we obtained interference signals corresponding to a protein monolayer. Finally, using a surface prepared as described above, biomolecul ar interaction experiments with an antibody against estrone were carried ou t to show the quality of the transducer surface. With RIfS all of the affin ity-based surface modifications can be detected online and time resolved. ( C) 2000 Academic Press.