A label-free electrochemical immunosensor with a novel signal production and amplification strategy based on three-dimensional pine-like Au–Cu nanodendrites

Abstract

A simple and novel label-free electrochemical immunosensor based on a bimetallic alloy was fabricated in this work. Three-dimensional (3D) pine-like Au–Cu nanodendrites (NDs) electrodeposited on the bare glassy carbon electrode (GCE) were employed as transducing materials to achieve the production and amplification of the electrochemical signal. The electrochemical detection was based on the fact that the immunocomplex can hinder the direct electron transfer in the redox process of Cu. Cu, instead of the traditional redox electron mediators, was exploited as a new signal producer. Au with good electron transfer ability could act as signal amplifier and capture antibodies. In addition, the 3D pine-like morphology of Au–Cu NDs with large specific surface area was beneficial to the immobilization of antibodies and the electron transfer between protein and metal. Under the optimal conditions, by using carbohydrate antigen 724 (CA724) as the target analyte, the label-free electrochemical immunosensor exhibited a wide linear range from 0.5 pg mL⁻¹ to 500 ng mL⁻¹ and a low detection limit of 0.25 pg mL⁻¹. The proposed immunosensor also displayed a satisfying electrochemical performance with good reproducibility, selectivity and stability. In this sense, this novel method will provide a new promising application for the clinical immunoassay of other biomarkers.