An electrochemical immunosensor for CEA detection based on Au-Ag/rGO@PDA nanocomposites as integrated double signal amplification strategy

An electrochemical immunosensor for quantitation of carcinoembryonic antigen (CEA) based on Au-Ag/rGO@PDA nanocomposites for dual signal amplification strategy was designed. Polydopamine-coated Ag/graphene hybrids were synthesized by one-step reduction and functionalization, and the dopamine was introduced to replace some reducing agents that are harmful to organisms. Silver nanoparticles modified on the electrodes produced sensitive electrochemical redox peaks. When different amounts of protein (antigen, antibody, bovine serum protein, etc.) were adsorbed on the surface of nano-silver, the surface of nano-silver was covered. The electrochemical redox peak of silver particles decreased due to the change of the effective area of bare silver particles which could react with electrodes. In addition, CEA-antibody (anti-CEA) was immobilized into a biocompatible nanocomposite of Au nanoparticles as a conductive matrix, and CEA-antibody (anti-CEA) was combined with Ag/rGO@PDA to form a dual signal amplifying element. Under optimal condition, the linear relationship was obtained from 0.001 ng mL−1 to 80 ng mL−1 between current signal and CEA concentration with a detection limit of 0.286 pg mL−1 (signal-to-noise ratio is 3). The label-free electrochemical immunosensor has been successfully applied to human serum detection due to good selectivity, stability and reproducibility.