Sensitive label-free electrochemical immunoassay based on a redox matrix of gold nanoparticles/Azure І/multi-wall carbon nanotubes composite

A sensitive label-free electrochemical immunosensing platform was designed by a redox matrix of gold nanoparticles (GNPs), Azure І and multi-wall carbon nanotubes (MWCNT) self-assemblying nanocomposite. To construct the immunosensor, MWCNT was first dispersed in Nafion (Nf) to obtain a homogeneous solution and then it was dropped on the surface of the gold electrode (Au). Then the positively-charged redox molecule, Azure І, was entrapped into MWCNT–Nf film to form a redox nanostructural membrane. Next, the negatively charged gold nanoparticles (GNPs) were assembled to the interface through the electrostatic force. Finally, carcinoembryonic antibody molecules could be absorbed into the GNPs/Azure І/MWCNT–Nf immobilization matrix. Using carcinoembryonic antigen (CEA) as a model protein, the electrochemical immunosensor exhibited good stability and reproducibility, as well as good selectivity and storage stability. This strategy presented a promising platform for sensitive and facile monitoring of CEA.

► In this work we construct the GNPs/Azure І/MWCNT–Nf matrix for the CEA antibody immobilization.
► The GNPs/Azure І/MWCNT–Nf matrix provides porous nanostructure, good electrochemical redox reversibility and biocompatibility.
► Based on the direct immunoassay format, the label-free immunosenors achieve a broader linear range, high sensitivity and good stability.