A potentiometric aptasensor for carcinoembryonic antigen (CEA) on graphene oxide nanosheets using catalytic recycling of DNase I with signal amplification

Abstract

A new and label-free potentiometric aptasensing platform was designed for the sensitive detection of carcinoembryonic antigen (CEA) in human serum on a graphene oxide (GO) nanosheet-modified glassy carbon electrode by coupling with target recycling-assisted signal amplification. To construct such a signal-amplification aptasensing system, the nanosheets were initially immobilized on the electrode through physical adsorption, and then CEA aptamers were coated on the nanosheets via π-stacking interaction. Upon target CEA introduction, the analyte reacted with the aptamer to form a complex, thus resulting in the dissociation of the aptamer from the nanosheets. The formed CEA–aptamer complexes were cleaved in the presence of DNase I to release target CEA, thereby triggering the target recycling and catalytic recycling of DNase I. Thanks to the negatively charged oligonucleotide skeleton, the dissociation of the aptamers from the nanosheets could cause a change in the local electrical potential of the modified electrode. Under optimum conditions, the shift in the potential increased with the increment of target CEA concentrations, and exhibited good potential responses within a linear range of 0.01–100 ng mL⁻¹ at a low detection limit of 9.4 pg mL⁻¹. The specificity, precision, reproducibility and stability of the potentiometric aptasensor were acceptable. The accuracy of this method was evaluated for the analysis of human serum specimens, giving well-matched results with those obtained from the commercial human CEA ELISA kit.