A frogspawn-like Ag@C core–shell structure for an ultrasensitive label-free electrochemical immunosensing of carcinoembryonic antigen in blood plasma

A three-dimensional (3D) frogspawn-like structure was achieved by simply coating nano-carbon outside silver nanospheres (Ag@C NFS) and used as a probe to capture the anti-carcinoembryonic antigen for the electrochemical immunosensing of carcinoembryonic antigen (CEA), a typical biomarker of several diseases such as gastric cancer, intestinal cancer and colon cancer. Moreover, Ag@C nanocables (Ag@C NCs) were aslo synthesized. By comparison, the globular 3D frogspawn-like structure endowed Ag@C NFS with a larger surface area, which is preferred to improve the capability of loading antibodies, higher water solubility, better biocompatibility and improved electrical conductivity, which was likely attributed to the synergistic effects of Ag and crystalline graphite carbon and the different structure with more hydroxyl groups exposed. Therefore, the resultant Ag@C NFS was used as an electrochemical immunosensing platform to fabricate a label-free immunosensor for the analysis of CEA, which showed an excellent immunosensing performance with a wide linear CEA detection range from 0.0001 ng mL(−1) to 100 ng mL(−1) and a low detection limit of 5.12 pg mL(−1). In particular, the good reproducibility, high stability and specificity of the proposed immunosensor ensured the successful application in the quantitative determination of CEA in cancerous human serum samples, providing a promising alternative to detect other biomarkers.