DNA hairpin dimer-mediated dual-catalysis circuit for efficient and amplifiable electrochemical biosensing

Exploring a variable catalytic hairpin assembly to amplify specific input might be intriguing for electrochemically detecting short-stranded DNA segment related to U. virens (iDNA). Herein, we proposed the first concept of hairpin dimer-mediated Dual-Catalysis Circuit (hdDCC) for creating rapid and efficient electrochemical biosensor. For proof-of-concept, we designed two functional hairpins (H1 and H2) both ended by a sulfhydryl (-SH) group. H1 was recognizable to iDNA, and H2 was modified with electroactive ferrocene (Fc) for signal readout. Under certain condition, two -SH groups were oxidized to form a disulfide bond (S-S), thus linking two mono-hairpins into their own dimers (dH1 or dH2). Upon presenting iDNA, the hdDCC was operated progressively via two consecutive cross-hybridization and displacement events among iDNA, dH1, dH2 and another helping hairpin. During this process, iDNA and dH1 as two cooperative catalysts were repeatedly displaced to accelerate the transduction and amplification, guiding the immobilization of Fc tags in the modified electrode surface for outputting significant current signal. Due to the structural confinement, two reactive units of hdDCC were closely oriented in shorter spatial distance to increase their local concentration, enabling rapider reaction kinetics and more efficient yield. By introducing hairpin dimers for dual-catalysis recycles, this strategy would provide a new paradigm to extend more extensive applications of typical catalytic hairpin assemblies, particularly in the disease prevention of agricultural crops.