A　novel　class　of　molecular　tags,　cadmium　ion-doped　magnetic　poly(styrene-acrylic　acid)　nanospheres　(Cd-MPSA),　was　first　synthesized　and　functionalized　with　polyclonal　rabbit　anti-human　luteinizing　hormone　antibodies　(PAb　2)　for　highly　efficient　electrochemical　immunoassay　of　luteinizing　hormone　(LH).　Transmission　electron　microscope　(TEM)　and　Fourier　transform　infrared　spectroscope　(FTIR)　were　employed　to　characterize　the　prepared　Cd-MPSA.　By　using　Cd-MPSA-labeled　PAb　2　as　molecular　tags,　a　novel　sandwich-type　immunoassay　protocol　was　built　for　determination　of　LH　on　monoclonal　mouse　anti-human　luteinizing　hormone　antibody　(MAb　1)-functionalized　gold　electrode.　The　assay　was　carried　out　in　pH　5.3　HAc-NaAc　buffer　solution　by　square　wave　voltammetry　(SWV).　The　signal　was　obtained　by　the　reduction　of　the　doped　cadmium　ions　in　the　Cd-MPSA.　Under　optimal　conditions,　the　currents　increased　with　the　increasing　LH　level　in　the　sample,　and　exhibited　a　linear　range　from　0.25　to　240mIUmL　-1　with　a　detection　limit　of　0.08mIUmL　-1　LH　at　3s　B.　The　precision,　reproducibility,　and　specificity　were　acceptable.　No　obvious　difference　was　encountered　in　the　analysis　of　spiking　LH　samples　into　newborn　calf　serum　with　the　referenced　values.　©　2012　Elsevier　B.V.