Trimetallic nanoparticle-decorated MXene nanosheets for catalytic electrochemical detection of carcinoembryonic antigen via Exo III-aided dual recycling amplifications

Changes in trace levels of tumor markers are important indicators for diagnosing and treating different diseases, including cancers. On account of a recycled dual amplification approach aided by exonuclease III (Exo III) and the trimetallic nanoparticle-decorated MXene nanosheet (Au-Pd-Pt/Ti3C2Tx)-modified electrode as the catalytic sensing interface, we describe the establishment of a label-free and aptamer-based sensitive carcinoembryonic antigen (CEA) detection assay platform. The target CEA molecules bind the aptamer containing hairpin probes to trigger cyclic cleavage of the secondary hairpins with the assistance of Exo III to release a large amount of ssDNAs, which further hybridize with the G-quadruplex-integrated triple-helix complex (THC) signal probes on the sensor electrode. Exo III then cyclically cleaves the resulting duplexes to liberate many G-quadruplex sequences that can confine hemin on the electrode surface. Subsequent catalytic reduction of H2O2 mediated by hemin on Au-Pd-Pt/Ti3C2Tx-modified sensing interface thus yields drastically enhanced current signals for detecting CEA with high sensitivity between 1 fg mL−1 and 1 ng mL−1 with the detection limit of 0.32 fg mL−1. Such a demonstration of our assay method for CEA indicates that the developed sensing platform can be extended as a promising means for sensitive monitoring of different molecular biomarkers.