A　class　of　novel　redox-active　hybrid　nanostructures　comprising　of　metal　platinum　and　ordered　mesoporous　carbon　(Pt-MSC)　was　designed　as　molecular　tags　for　sensitive　electrochemical　immunoassay　(alpha-fetoprotein,　AFP,　as　a　model　analyte)　on　the　cyclodextrin-functionalized　graphene　sensing　platform.　To　construct　such　a　molecular　tag,　a　layer　of　positively　charged　thionine　was　initially　adsorbed　onto　the　MSC　through　negatively　charged　carboxyl　groups,　and　[PtCl　6]　2-　ions　were　then　conjugated　onto　the　thionine/MSCs,　followed　by　in　situ　reducing　to　metal　platinum.　Finally,　horseradish　peroxidase-labeled　anti-AFP　(HRP-anti-AFP)　was　conjugated　onto　the　metal　platinum　surface.　A　sandwich-type　immunoassay　format　was　employed　for　determination　of　AFP　by　using　the　labeled　HRP　toward　the　reduction　of　H　2O　2　with　the　aid　of　thionine　in　pH　6.5　acetic　acid-buffered　solution.　Under　optimal　conditions,　the　developed　immunoassay　displayed　a　wide　linear　range　from　2.0　pg/mL　to　10.0　ng/mL　toward　AFP　standards　with　a　low　detection　limit　(LOD)　of　1.5　pg/mL　at　3σ.　The　precision,　selectivity　and　stability　were　acceptable.　Clinical　serum　specimens　were　assayed　with　the　method,　and　the　results　were　received　in　good　accordance　with　those　obtained　from　the　referenced　electrochemiluminescent　immunoassay　method.　©　2012　Elsevier　Ltd.　All　rights　reserved.