Carbon Nanomaterials-based Electrochemical Immunoassay with -Galactosidase as Labels for Carcinoembryonic Antigen

In this study, a novel signal-amplified strategy for sensitive electrochemical sandwiched immunoassay of carcinoembryonic antigen (CEA) was constructed based on aminofunctionalized graphene oxide (GO-NH2) supported AgNPs used as catalytic labels of secondary anti-CEA and -galactosidase (-Gal), Meanwhile, sulfhydrylation single-wall carbon nanotubes (SWCNTs-SH) as substrate materials embellished gold electrode through Au-SH and connected with gold nanoparticles to form anti-CEA/AuNPs/SWCNTs-SH/Au sensing platform through layer-by-layer. In the presence of analyte CEA, a sandwich-type immunoassay format was employed for determination of CEA by using the labeled -Gal toward the reduction of p-aminophenyl galactopyranoside (PAPG) and the redox reaction of AgNPs. Under optimal conditions, the increase in the current was proportional to the concentration of CEA from 0.1pg/mL to 200ng/mL. The detection limit (LOD) was 0.036pg/mL CEA at 3 sigma. The electrochemical immunoassay displayed an acceptable precision, selectivity, stability. Clinical serum specimens were assayed with the method, and the results were in acceptable agreement with those obtained from the referenced electrochemiluminescent method.