A tris (2,2′-bipyridyl)cobalt(III)-bovine serum albumin composite membrane for biosensors

A concept based on a novel redox-biocompatible composite protein membrane fabrication, double enzyme membrane modification technique and antibody immobilization, was exploited to develop a highly sensitive amperometric enzyme immunosensor for detection of carcinoembryonic antigen (CEA). In this concept, a solution of bovine serum albumin (BSA) containing horseradish peroxidase (HRP) is coated on the gold electrode in such a way that the first enzyme membrane is achieved. Then tris(2,2'-bipyridyl) cobalt(III) (Co(bpy)(3)(3+)), as a mediator, was embedded in BSA-HRP composite membrane vis the electrostatic force and hydrophobe functions. Later a self-assembled conductive nano-Au monolayer was constructed onto the resultant electrode surface by electrostatic interaction between the negatively charged nano-Au and positively charged Co(bpy)(3)(3+). Protein A is used as a binding material to achieve an adjusted (but not 3 random) orientation of the antibodies surface for efficient combination of antigens. Finally, the HRP, was employed to block the possible remaining active sites and avoid the non-specific adsorption, which acts not only as a blocking reagent instead of the commonly used BSA but also as the conventional enzyme-labeling to amplify the response of the antigen-antibody reaction. The immunosensor constructed with the double layer biocatalytic HRP membranes and the desirable Co(bpy)(3)(3+)/BSA redox-biocompatible composite membrane performed high sensitivity and a wide linear response to CEA in the range of 0.50-80.00 ng/mL with a limit of detection of 0.14ng/mL, as well as good stability and long-term life. (c) 2006 Elsevier Ltd. All rights reserved.