Copper-enhanced electrochemical immunosensor based on gold nanoparticles for the quality control of hepatitis A virus vaccines

A voltammetric sandwich immunosensor based on gold nanoparticles (AuNPs) conjugates and specific immunoglobulins (IgG@AuNPs) has been developed for the quantitative determination of inactivated hepatitis A virus (HAV) in a vaccine. For the first time, copper nanoparticles (CuNPs) were catalytically reduced from copper sulfate on the surface of AuNPs conjugates by a chemical reducing agent, reduced nicotinamide adenine dinucleotide (NADH). Control experiments showed that copper was not formed in the absence of AuNPs on the electrode surface or in the absence of NADH. The AuNPs and IgG@AuNPs conjugates before and after the reduction of CuNPs were characterized by transmission electron microscopy (TEM). A carbon-based screen-printed electrode (SPE), functionalized with laser reduced graphene oxide (LRGO) to enhance the conductivity of its working surface, was employed as the solid substrate for immobilizing the receptor layer. This layer consisted of ‘capture’ antibodies derived from rabbits immunized with HAV. During the development of the electrochemical immunosensor, particular attention was paid to the optimization of the conditions for the deposition time of copper on the surface of the gold particles of the IgG@AuNPs conjugates and the concentration of the reducing agent NADH. The elemental composition and electronic state of the atoms on the surface of the electrodes modified with AuNPs before and after the reduction of CuNPs with NADH were investigated by X-ray photoelectron spectroscopy (XPS). This study demonstrates that the electrochemical immunosensor amplifies the analytical signal from copper electrooxidation in biosensor for detecting HAV in vaccines. Concurrently, it reduces immunoassay costs and viral antigen detection time relative to traditional enzyme-linked immunosorbent assay (ELISA) systems.