Not Just Gold: Engineering Nucleic Acid Probes onto Peptide Hydrogel Biointerface for Electrochemical Detection of miRNA

Surface engineering critically influences the analytical performance, manufacturability, and translational potential of electrochemical nucleic acid biosensors. Here, we introduce a peptide hydrogel (HG)-based surface engineering strategy that replaces conventional Au−thiol functionalization with a single supramolecular biointerface for disposable electrochemical biosensors. An HG based on Fmoc-FF/Fmoc-FFKK-Amide (1:2, v/v) enabled the direct immobilization of DNA probes onto disposable screen-printed electrodes, integrating electrode functionalization and probe immobilization within a single material and eliminating the multistep workflow associated with conventional immobilization strategies. The resulting platform required approximately 45 min for fabrication while reducing the consumption of costly surface-functionalization reagents, yielding disposable sensors with an estimated fabrication cost of approximately €0.60 per device. Following target hybridization, electrochemical measurements could be performed directly without additional surface-processing or labeling steps. As a proof of concept, the biosensor enabled amplification-free detection of miRNA-107 over the 0.1−1000 nM concentration range, achieving detection limits of 0.3 nM in PBS and 0.6 nM in undiluted human serum with a relative standard deviation below 4%. More broadly, this work establishes supramolecular peptide HG beyond passive scaffolds, positioning them as functional biointerfaces for the next generation of portable, cost-effective, and user-friendly electrochemical nucleic acid biosensors.