Sandwich-type electrochemiluminescence immunosensor based on poly(acrylic acid) coated Fe 3 O 4 composite for human chorionic gonadotrophin detection using quantum dots functionalized CNTs as labels

In this work, an easy approach was reported to synthesize novel poly(acrylic acid) coated Fe 3 O 4 magnetic nanoparticles which showed high water solubility and biocompatibility. Primary antibodies were immobilized onto the surface of the prepared nanoparticles using cysteine as a coupling agent. A large number of negatively charged CdTe quantum dots were coated on the poly(diallyldimethylammonium chloride) coated carbon nanotubes via self-assembly electrostatic reactions, and used as carriers of secondary antibodies, which could significantly amplify the electroluminescence signal. Coupled with a microfluidic strategy, the electroluminescence immunosensors could be easily separated and assembled on the surface of indium tin oxide glass with external magnetic forces. With a sandwich-type immunoassay format, the electroluminescence intensity increased linearly with the logarithm of the human chorionic gonadotrophin concentration in the range of 0.005–50 ng cm −3 and the detection limit was 2.8 pg cm −3 . In particular, this approach has the advantages of high sensitivity, specificity, and stability and could become of great promise for clinical application. Graphical Abstract .