Multi-walled carbon nanotubes–chitosan with a branched structure modified with ferrocenecarboxylic acid for carcinoembryonic antigen detection

Abstract

In this article, a novel electrochemical immunosensor was proposed based on ferrocenecarboxylic acids (Fc-COOH) connected to the branched structure of an electrode surface for the detection of carcinoembryonic antigen (CEA). The electrode was first modified with multi-walled carbon nanotubes–chitosan (MWCNT–CS) complexes, and the MWCNT–CS coating contains active secondary reaction functional entities that could form covalent bonds with molecules containing carboxyl or aldehyde groups. A large number of Fc-COOH groups were connected to the branched structure of the electrode surface, and then the electrode was further modified with polydopamine (PDA) and gold nanoparticles (AuNPs), which not only provided a favorable microenvironment and increased the loading capacity of the biomolecules to maintain the activity of the immobilized biomolecules, but also enhanced the conductivity and charge-transport properties of the modified electrode. Under optimal conditions, the immunosensor showed a low limit of detection (0.002 ng mL⁻¹) and a wide linear range (0.01–80 ng mL⁻¹). With the merits of acceptable stability, high sensitivity, the wide linear range and the low detection limit, the new immunosensors show great potential in the field of analytical applications.