Ultrasensitive Detection of ctDNA by Target-Mediated In Situ Growth of DNA Three-Way Junction on the Electrode

Circulation tumor DNA (ctDNA) is an emerging biomarker for diagnosis and therapy of cancers. Herein, an ultrasensitive electrochemical method for ctDNA quantification is developed by in situ growth of DNA three-way junction on the electrode. Three hairpin-structured DNA probes are used as fuel strands and strand-displacement polymerization reactions are initiated by target ctDNA for the in situ growth of the DNA junction structure, which changes the electron transfer pathways of electrochemical species. By further employing a reductant-mediated amplification, the method shows sub-femtomolar sensitivity. Meanwhile, specific analysis of ctDNA is achieved with negligible interference by DNAs with one or more mismatched sites. Therefore, the proposed method may have great analytical and clinical applications.