Catalytic Hairpin Assembly-Programmed DNA Three-Way Junction for Enzyme-Free and Amplified Electrochemical Detection of Target DNA.

DNA three-way junctions (DNA 3WJ) have been widely used as important building blocks for the construction of DNA architectures and dynamic assemblies. Herein, we describe for the first time a catalytic hairpin assembly-programmed DNA three-way junction (CHA-3WJ) strategy for the enzyme-free and amplified electrochemical detection of target DNA. It takes full advantage of the target-catalyzed hairpin assembly-induced proximity effect of toehold and branch-migration domains for the ingenious execution of the strand displacement reaction to form the DNA 3WJ on the electrode surface. A low detection limit of 0.5 pM with an excellent selectivity was achieved for target DNA detection. The developed CHA-3WJ strategy also offers distinct advantages of simplicity in probe design and biosensor fabrication, as well as enzyme-free operation. Thus, it opens a promising avenue for applications in bioanalysis, design of DNA-responsive devices, and dynamic DNA assemblies.