A novel electrochemical aptamer biosensor based on tetrahedral DNA nanostructures and catalytic hairpin assembly for CEA detection

At present, carcinoembryonic antigen (CEA) is a commonly used biomarker to diagnose cancers. Accurate and specific detection of CEA in clinical samples is of great significance for the diagnosis, treatment and prognosis of related cancers. In this research, we developed an enzyme-free electrochemical aptamer biosensor for highly sensitive detection of CEA based on tetrahedral DNA nanostructures (TDNs) and target-assisted catalytic hairpin assembly (CHA). A long single strand (Trigger), five oligonucleotide chains (S1-S5) and CEA aptamer were designed to form TDN-aptamer and TDN-H1 respectively. In the presence of CEA, the aptamer designed at the top of TDN-aptamer specifically bound to CEA, while trigger was released to open H1 immobilized on the top of TDN-H1. This reaction initiated the CHA cycle with the participation of H2 modified by Methylene blue (MB). Subsequently, a large number of MB modified H1-H2 double strands were connected to the electrode surface through TDN structures, which generated significant current signals. This proposed biosensor could detect CEA down to 0.04567 pg mL−1 with a wide linear range from 1 pg mL−1 to 30000 pg mL−1. Furthermore, the electrochemical aptamer biosensor could detect CEA in serum samples accurately, it provided an effective alternative platform for clinical detections of CEA.