A　facile　and　feasible　magneto-controlled　immunosensing　platform　was　designed　for　sensitive　electrochemical　immunoassay　of　brevetoxin　B　(BTX-2)　in　seafood　by　using　guanine-assembled　graphene　nanoribbons　(GGNRs)　as　molecular　tags　on　a　home-made　magnetic　carbon　paste　electrode.　Initially,　monoclonal　mouse　anti-BTX-2　antibodies　were　covalently　immobilized　on　the　surface　of　magnetic　beads,　which　were　used　as　the　immunosensing　probes　for　the　capture　of　BTX-2.　The　recognition　elements　were　prepared　by　chemical　modification　of　bovine　serum　albumin-BTX-2　conjugates　(BTX-2-BSA)　with　the　GGNRs.　Based　on　a　competitive-type　immunoassay　format,　the　formed　magnetic　immunocomplex　was　integrated　on　the　electrode　with　an　external　magnet,　followed　by　determination　in　pH　6.5　phosphate-buffered　solution　containing　2　mu　M　Ru(bpy)(3)Cl-2.　Under　optimal　conditions,　the　electrochemical　signals　decreased　with　the　increasing　BTX-2　concentrations　in　the　sample.　The　dynamic　concentration　range　spanned　from　1.0　pg　mL(-1)　to　10　ng　mL(-1)　with　a　detection　limit　of　1.0　pg　mL(-1)　BTX-2.　Inter-　and　intra-batch　assay　precisions　were　substantially　improved　by　resorting　to　the　GGNR　manifold.　The　method　featured　unbiased　identification　of　negative　(blank)　and　positive　samples.　No　significant　differences　at　the　95%　confidence　level　were　encountered　in　the　analysis　of　12　spiked　samples　including　S.　constricta,　M.　senhousia　and　T.　granosa　between　the　electrochemical　immunoassay　and　commercially　available　enzyme-linked　immunosorbent　assay　(ELISA)　for　determination　of　BTX-2.　(c)　2012　Elsevier　B.V.　All　rights　reserved.