A high-sensitivity electrochemical aptasensor of carcinoembryonic antigen based on graphene quantum dots-ionic liquid-nafion nanomatrix and DNAzyme-assisted signal amplification strategy

•Pb2+dependent DNAzyme electrochemical biosensor for carcinoembryonic antigen detection was developed.•The graphene quantum dots-ionic liquid-nafion composite film was fabricated on electrode for the first time.•The target-aptamer complex recycling led to continuous cleavage of substrate chain and amplified electrochemical signal.•The method has been applied in human serum, with high selectivity and good recovery.

In this work, we have developed an electrochemical aptasensor for high-sensitivity determination of carcinoembryonic antigen (CEA) based on lead ion (Pb2+)-dependent DNAzyme-assisted signal amplification and graphene quantum dot-ionic liquid-nafion (GQDs-IL-NF) composite film. We designed hairpin DNA containing CEA-specific aptamers and DNAzyme chains. In the presence of CEA, hairpin DNA recognized the target and performed a DNAzyme-assisted signal amplification reaction to yield a large number of single-stranded DNA. The GQDs-IL-NF composite film was immobilized on the glassy carbon electrode for the interaction with single-stranded DNA through noncovalent π-π stacking interaction. Therefore, the methylene blue-labeled substrate DNA (MB-substrate) was fixed on the electrode and exhibited an initial electrochemical signal. Under optimal conditions, the response current change was proportional to the concentration of CEA, demonstrating a wide linear range from 0.5 fg mL−1 to 0.5 ng mL−1, with a low detection limit of 0.34 fg mL−1. Furthermore, the proposed aptasensor was successfully applied in determining CEA in serum samples, showing its superior prospects in clinical diagnosis.