Ultrasensitive electrochemiluminescence biosensor for the detection of carcinoembryonic antigen based on multiple amplification and a DNA walker

A novel electrochemiluminescence (ECL) biosensor based on enzyme-aided multiple amplification and a deoxyribozyme-driven DNA walker was designed to achieve highly sensitive detection of carcinoembryonic antigen (CEA). When the present target CEA was combined with the aptamer, the trigeminal DNA structure was formed with the use of primers and templates, and polymerization amplification reactions were carried out with the assistance of enzymes, generating a large number of product chains (DNA walker) with the DNAzyme sequence. Then, the DNA walker hybridized with the DNA-CdSe quantum dot (QD) signal probe on the electrode surface, and the Pb2+ ion-assisted DNAzyme enabled the DNA signal probes to be cyclically clipped, resulting in a significant decrease in the QD ECL signal for the sensitive detection of CEA. The change value of the ECL signal is linearly related to the logarithm of CEA concentration in the range from 1.0 fg/mL to 100 ng/mL, and the detection limit is 0.21 fg/mL. This DNAzyme-driven DNA walker can be used to design versatile biosensors to achieve "signal-off" or "signal-on" detection by shearing many kinds of signal or quenching probes. Thus, this research provides a new promising strategy for the CEA assay and is expected to be used in the early diagnosis of tumours.