Ag@Fe 2 O 3 -graphene oxide nanocomposite as a novel redox probe for electrochemical immunosensor for alpha-fetoprotein detection

In this paper, a high sensitivity label-free electrochemical immunosensor for alpha-fetoprotein (AFP) detection using Ag@Fe2O3-graphene oxide (GO) nanocomposite (Ag@Fe2O3-GO) as a new type of redox nano-probe is reported. The Ag@Fe2O3-GO nanocomposite with tunable loading density up to full monolayer coverage is synthesized by adopting a simple phase transfer method and applied as a redox probe to fabricate an immunosensor for AFP. The obtained Ag@Fe2O3-GO nanocomposite has favorable electrical conductivity with the advantage of biocompatibility and chemical stability, which improves both the sensitivity and stability of the immunosensor. Furthermore, due to their excellent conductivity and large surface area, gold–platinum alloy nanoparticles (Au–Pt NPs) are served to immobilize an antibody (anti-AFP) and the electrochemical signal is further amplified accompanied by the enhanced sensitivity and the stability of the immunosensor. The novel Ag@Fe2O3-GO nanocomposite probe for AFP detection developed in this work exhibits excellent sensitivity with a linear response in the concentration range from 0.005 to 100 ng mL−1 and a detection limit of 0.2 pg mL−1 (S/N = 3).