MOLECULAR RECOGNITION AT SELF-ASSEMBLED MONOLAYERS - THE CONSTRUCTION OF MULTICOMPONENT MULTILAYERS

A multilayer system of proteins and organic thiols self-assembled on a gold surface, and with a different component in each layer, is investigated. The multilayer system chosen-biotinylated thiol; streptavidin; biotinylated Fab; human chorionic gonadotrophin; monoclonal antibody-is of relevance to immunoassays for pregnancy testing. The composition of the first thiol monolayer is shown to have a strong influence on the binding properties of all subsequent layers-not only in the efficiency of binding, but also in its specificity. The efficiencies of the binding processes between the different layers are analyzed. The sensitivity of the system to human chorionic gonadotrophin is measured and a detection limit of approximately 1 x 10(-8) M determined.