Highly-sensitive label-free electrochemical carcinoembryonic antigen immunosensor based on a novel Au nanoparticles–graphene–chitosan nanocomposite cryogel electrode

• A novel highly sensitive electrochemical immunosensor based on a cryogel modified electrode was developed.
• For the first time, a cryogel was prepared from Au nanoparticles–graphene–chitosan (AuNPs–GP–CS) nanocomposite.
• The AuNPs–GP–CS cryogel gave a 1.7 times higher sensitivity than a non-cryogel electrode.
• LOD of the AuNPs–GP–CS nanocomposite cryogel was 25 times lower than a non-cryogel electrode.
• For serum samples, this method showed no significantly difference to the conventional analysis (P > 0.05).

For the first time, a simple and highly sensitive label-free electrochemical carcinoembryonic antigen (CEA) immunosensor based on a cryogel electrode has been developed and tested. The as-prepared nanocomposite combined the advantages of the graphene, AuNPs and chitosan (AuNPs–GP–CS) together with the ease of preparing a cryogel coupled to a silver deposition, to act as a redox mediator, on a Au electrode. Under the optimal conditions, the decrease of the cyclic voltammetry (CV) silver peak current was proportional to the CEA concentration over a range of from 1.0 × 10−6 to 1.0 ng mL−1 with a detection limit of 2.0 × 10−7 ng mL−1. This AuNPs–GP–CS cryogel electrode gave a 1.7 times higher sensitivity and 25 times lower detection limit than the non-cryogel electrode. Moreover, the proposed electrochemical immunosensor exhibited good selectivity, reproducibility and stability. When applied to analyse clinical serum samples, the data determined by the developed immunosensor were in agreement with those obtained by the current hospital analysis system (enzyme linked fluorescent assay) (P > 0.05), to indicate that the immunosensor would be potentially useful for clinical diagnostics.

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