A　feasible　and　practicable　amperometric　immunoassay　strategy　for　sensitive　screening　of　carcinoembryonic　antigen　(CEA)　in　human　serum　was　developed　using　carbon　nanotube　(CNT)-based　symbiotic　coaxial　nanocables　as　labels.　To　construct　such　a　nanocable,　a　thin　layer　of　silica　nanoparticles　was　coated　on　the　CNT　surface　by　sonication　and　sal-gel　methods,　and　then　colloidal　gold　nanoparticles　were　assembled　on　the　amino-functionalized　SiO2/CNTs,　which　were　used　for　the　label　of　horseradish　peroxidase-anti-CEA　conjugates　(HRP-anti-CEA-Au/SiO2/CNT).　In　the　presence　of　analyte　CEA,　the　sandwich-type　immunocomplex　was　formed　on　an　anti-CEA/Au/thionine/Nafion-modified　glassy　carbon　electrode　by　using　HRP-anti-CEA-Au/SiO2/CNTs　as　detection　antibodies.　To　embody　the　advantages　of　the　protocol,　the　analytical　properties　of　variously　modified　electrodes　were　compared　in　detail　on　the　basis　of　different　nanolabels.　Under　optimal　conditions,　the　cathodic　peak　currents　of　the　electrochemical　immunosensor　were　proportional　to　the　logarithm　of　CEA　concentration　over　the　range　from　0.01　to　12　ng　mL(-1)　in　pH　5.5　HAc-NaAc　containing　5　mM　H2O2.　At　a　signal-to-noise　ratio　of　3,　the　detection　limit　(LOD)　is　5　pg　mL(-1)　CEA.　Intra-　and　inter-assay　coefficients　of　variation　were　below　9.5%.　Meanwhile,　the　selectivity　and　stability　of　the　immunosensor　were　acceptable.　In　addition,　the　technique　was　evaluated　by　spiking　CEA　standards　in　pH　7.4　PBS　and　with　35　clinical　serum　specimens,　receiving　excellent　accordance　with　results　from　commercially　available　electrochemiluminescent　enzyme-linked　immunoassay.　(C)　2011　Elsevier　B.V.　All　rights　reserved.