Electrochemical DNA detection via exonuclease and target-catalyzed transformation of surface-bound probes

We report a single-step, single-reagent, label-free, isothermal electrochemical DNA sensor based on the phenomenon of target recycling. The sensor exploits strand-specific exonuclease activity to achieve the selective enzymatic digestion of target/probe duplexes. This results in a permanent change in the probe structure that yields an increased faradaic current and liberates the intact target molecule to interact with additional detection probes to achieve further signal amplification. Using this architecture, we achieve an improved detection limit in comparison to hybridization-based sensors without amplification. We also demonstrate a 16-fold signal amplification factor at low target concentrations. Combined with the advantages of electrochemical detection and its ready integration with microelectronics, our approach may represent a promising path toward direct DNA detection at the point of care.