A novel electrochemical immunosensor based on nonenzymatic Ag@Au-Fe3O4 nanoelectrocatalyst for protein biomarker detection

A hybrid nanostructure of Fe3O4 nanospheres and Ag@Au nanorods prepared by polydopamine coating was utilized as nanoelectrocatalyst to construct a novel sandwich-type electrochemical immunosensor. Ag@Au-Fe3O4 nanohybrid modified electrode exhibited much better electrocatalytic activity toward the reduction of hydrogen peroxide than Fe3O4 nanospheres or Ag@Au nanorods due to the synergetic catalytic effect. The immunosensor was prepared by immobilizing the capture antibodies on the amine terminated nanocomposite of carbon nanofibers-chitosan, whilst the trace tag was prepared by loading detection antibodies on the Ag@Au-Fe3O4 nanocomposite. After the parameter optimization, the amperometric signal increased linearly with human IgG concentration in the broad range of 0.1 mu g to 5 mu g mL(-1) with a detection limit of 50 mu g mL(-1). Meanwhile, the enzyme-free catalyst based immunosensor also showed acceptable selectivity, reproducibility and stability. (C) 2016 Elsevier B.V. All rights reserved.