Development of an electrochemical biosensor based on rGO/Ag₂S-Au nanocomposites and L-CHA dual signal amplification for miR-155 detection

MicroRNA-155 (miR-155) is a critical biomarker implicated in various pathological processes, including cancer progression, immune response, and cardiovascular diseases. Consequently, accurate detection of miR-155 at low concentrations is essential for early diagnosis and effective treatment monitoring. To address this need, this study introduces a novel application of reduced graphene oxide/silver sulfide-gold (rGO/Ag₂S-Au) nanocomposites as signal tracers for the sensitive detection of miR-155. First, Ag₂S-Au nanoparticles were synthesized via in-situ reduction of HAuCl₄ on Ag₂S surfaces and then incorporated into rGO to form the nanocomposites. Subsequently, the composites were hybridized with signal probes to fabricate signal labels. In the detection mechanism, miR-155 triggers local catalytic hairpin assembly ( L -CHA) to amplify signals. Finally, the products were immobilized on capture probe-modified electrodes, and electrochemical responses were measured by differential pulse voltammetry (DPV). As a result, the biosensor exhibits a linear detection range from 1 fM to 1 μM, with a detection limit as low as 0.17 fM. Overall, this work advances electrochemical biosensor technology and provides valuable insights for high-performance biosensor design in rapid clinical diagnostics.