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A thin, organic film has been applied to the sensing area of a surface plasmon resonance sensor to provide specific sites for the covalent immobilization of proteins. Previously, protein binding experiments were carried out on the bare gold surface of this probe, or using a gold- thiol coupling technique. There has been great interest in increasing the probe sensitivity to protein binding reactions as well as maximizing the amount of protein immobilized in the sensor area. A new surface chemistry has been especially developed to meet these goals. This thin (approximately 200 angstroms) film is comprised primarily of a poly(ethylene oxide) (PEO)-like layer which provides a non-fouling base that resists non-specific protein uptake. Amine groups are distributed throughout this base, providing sites to which specific proteins can be immobilized using established chemistries. The two film components are deposited simultaneously by a radio frequency plasma deposition reaction. Film surface chemistry was studied by electron spectroscopy for chemical analysis (ESCA). By derivatizing the surface layer with pentafluorobenzaldehyde, using ESCA, we could relate surface fluorine signal to amine content. Data will be presented on the immobilization of biotin and the dynamic reaction of the immobilized biotin with streptavidin.
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