Nanogold-actuated biomimetic peroxidase for sensitized electrochemical immunoassay of carcinoembryonic antigen in human serum

A new electrochemical immunoassay protocol for the determination of carcinoembryonic antigen (CEA) in human serum was developed by means of immobilizing horseradish peroxidase-labeled anti-CEA antibodies (HRP-anti-CEA) on the nanogold/nano-Fe3O4 particles-functionalized polyion complex (PIC) membrane. With a one-step immunoassay format, the formed immunocomplex inhibited partly the bioactive center of the immobilized HRP, and decreased the HRP toward the reduction of H2O2. Nanogold-actuated nano-Fe3O4 mimetic peroxidase was used for the sensitivity improvement of the electrochemical immunosensor with Prussian blue (PB) as mediators. Under optimal conditions, the electrochemical immunosensor displayed a wide dynamic range of 0.1–220 ng mL−1 with a relative low detection limit (LOD) of 10 pg mL−1 CEA (at 3σ). Intra- and inter-assay show good precisions with a coefficient of variation (CV) lower than 7.8% and 7.3%, respectively. No significant difference at the 95% confidence level was encountered in the analysis of 17 human serum specimens between the electrochemical immunosensor and automatic electrochemiluminescent (ECL) analyzer for the determination of CEA.