Multi-armed　dendritic　polyaniline　nanofibers　(MPANFs)　were　first　synthesized　and　functionalized　with　horseradish　peroxidase　(HRP)　and　carcinoembryonic　antibody　(anti-CEA)　for　highly　efficient　electrochemical　immunoassay　of　carcinoembryonic　antigen　(CEA,　as　a　model　analyte　here)　in　this　work.　Transmission　electron　microscope　(TEM)　and　scanning　electron　microscope　(SEM)　techniques　were　employed　to　characterize　the　synthesized　MPANFs.　By　using　anti-CEA-conjugated　core-shell　gold-Fe　3O　4　nanocomposites　(GoldMag)　as　immunosensing　probes　and　biofunctionalized　MPANFs　as　molecular　tags,　a　new　sandwich-type　homogeneous　immunoassay　strategy　was　developed　for　the　determination　of　CEA　by　coupling　with　a　home-made　flow-through　magneto-controlled　microfluidic　device.　Under　optimal　conditions,　the　electrochemical　immunoassay　exhibited　a　wide　dynamic　range　of　four　orders　of　magnitude　from　1.0　pg　mL　-1　to　50　ng　mL　-1　with　a　low　detection　limit　of　0.1　pg　mL　-1　CEA　at　3σ.　Intra-　and　inter-assay　coefficients　of　variation　were　below　10%.　The　assayed　results　for　clinical　serum　specimens　with　the　electrochemical　immunoassay　were　received　in　good　accordance　with　the　results　obtained　from　the　referenced　enzyme-linked　immunosorbent　assay　(ELISA)　method.　©　The　Royal　Society　of　Chemistry　2012.