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.　(C)　2012　Elsevier　BM.　All　rights　reserved.