A novel label-free amperometric immunosensor for the determination of myeloperoxidase (MPO) based on poly-o-phenylenediamine (PoPD)-multi-wall carbon nanotubes (MWCNTs)-ionic liquid/ gold nanoparticles (nanogold) modified gold electrode (Au) was constructed. Firstly, a PoPD/MWNTs composite modified Au electrode was prepared in situ electropolymerization using ionic liquid as the supporting electrolyte. Then gold nanoparticles were adsorbed onto the electrode surface through amino-groups on the composite membrane for immobilization of MPO antibody via amine-Au affinity. The modification process was characterized by cyclic voltammetry (CV) and scanning electron microscope (SEM). The factors possibly influenced the performance of the proposed immunosensor were studied in detail. Under optimal conditions, the obtained immunosensor exhibited good electrochemical behavior to MPO in a linear range of 0.25 to 350 ng/mL (r＝0.9985), with a detection limit of 0.07 ng/mL. The immunosensor has advantages of good stability, regeneration, high sensitivity and specificity. Thus, the method can be used for clinical application of MPO analysis.

Key words: myeloperoxidase, immunosensor, ionic liquid, poly-o-phenylenediamine, multi-wall carbon nanotubes