Electrochemical immunosensor for carcinoembryonic antigen based on nanosilver-coated magnetic beads and gold-graphene nanolabels.

A novel redox-active magnetic nanostructure was synthesized by using a wet chemical method for high-efficiency electrochemical immunoassay of carcinoembryonic antigen (CEA, as a model analyte). The nanostructures based on the combination of a magnetic nanocore, a layer of electroactive poly(o-phenylenediamine) (PPD), and a silver metallic shell displayed good adsorption properties for the attachment of anti-CEA antibody selective to CEA. The magnetic nanostructure presented good redox behaviors to facilitate and modulate the way it was integrated into a magnetic carbon paste electrode. The assay was based on a sandwich-type immunoassay protocol by using nanogold-patterned graphene oxide nanoscales (AuNP-GO), conjugated with horseradish peroxidase-labeled anti-CEA, as secondary antibodies and biofunctionalized magnetic nanostructures as immunosensing probes. Under optimal conditions, the nanoparticle-based immunocomposites exhibited good electrochemical responses for the determination of CEA, and allowed the detection of CEA at a concentration as low as 1.0 pg mL(-1) at a signal-to-noise ratio of 3. In addition, the magnetic immunosensing had good reproducibility, and acceptable accuracy, and could be successfully applied for the detection of CEA in the clinical serum specimens. Significantly, by controlling the target biomolecules, this assay can be easily extended for use with other immunosensings, and thus represents a versatile design routine.