A major limitation of conventional nucleic acid (NA) biosensors is their dependence on surface-immobilised probes, which require time-consuming sensor preparation and prolonged exposure of the sensing surface to complex biological samples. During target capture, non-target species compete for surface access, leading to non-specific adsorption that compromises assay specificity, sensitivity, reproducibility, and speed. Here, we report a fundamentally different, amplification-free electrochemical sensing principle based on cathodic potential–induced adsorption of NA onto bare gold electrodes. In this approach, target NA is first isolated from complex samples using magnetic beads and then rapidly driven onto the electrode surface using a brief cathodic potential step (30 s), enabling immediate electrochemical readout without enzymatic amplification or surface modification. This potential-induced process accelerates NA capture by more than an order of magnitude compared with passive adsorption, while physically separating the sensing surface from the sample matrix to minimise non-specific interference.
The platform enables differential pulse voltammetric (DPV) detection of NA biomarkers with attomolar-level sensitivity and a total signal acquisition time of ~2 minutes (30 s adsorption plus 75 s measurement). We demonstrate its applicability across multiple application domains, including detection of microRNA from human trophoblast (BeWo) cell lines and genomic DNA from Xylella fastidiosa, one of the world’s most destructive plant pathogens. Across all targets, the method provides rapid, selective, and reproducible detection, with total assay times under 30 minutes, approximately fourfold faster than conventional molecular amplification workflows. By integrating potential-induced NA adsorption with bare-electrode electrochemistry, this work establishes a new paradigm for molecular diagnostics that is fast, low-cost, portable, and well suited for on-site deployment. Importantly, the underlying principle is not target- or pathogen-specific and can be readily extended to a wide range of biomedical, agricultural, and biosecurity applications, enabling accessible molecular diagnostics in both high- and low-resource settings.