Ultrafast Electrochemical Biosensor for SARS‐CoV‐2 Viral Nucleic Acids Sensitive Detection Using Os‐Complex/3D Vertical Graphene Dual Signal Amplification

A central challenge in rapid viral nucleic acid surveillance is the inherent trade‑off between assay speed and sensitivity. Herein, this study overcome this limitation with a dual‐signal amplification biosensor based on the synergistic integration of a chitosan‐anchored 3D vertical graphene (VG/CS) nanoarchitecture and a rationally designed catalytic osmium(II) complex (Os(5,6‐Me 2 phen) 3 2+ ). The VG/CS nanoarchitecture dramatically concentrates analytes at the electrode surface, driving efficient target enrichment, while the planar ligands of the Os complex ensure exclusive dsDNA binding and amplified electrochemical reporting. Under optimized conditions, this synergy achieves a detection limit of 1.93 fM for synthetic dsDNA in just 3 min and delivers a 2.3‐order‐of‐magnitude sensitivity enhancement compared to conventional 2D graphene sensors. Clinically, the platform completes a full swab‐to‐result workflow for SARS‑CoV‑2 RNA in only 6 min—detecting as few as 2000 copies/mL with perfect agreement to qRT‑PCR (κ = 1.00, n = 18). Beyond viral RNA, the sensor adapts readily to other nucleic acid biomarkers: when coupled with isothermal amplification, it sensitively quantifies microRNA‑21 at femtomolar levels. Moreover, the device exhibits exceptional operational stability and anti‐fouling performance, retaining over 93 % of its signal intensity in complex biological media. By elegantly resolving the speed‐sensitivity dilemma through a novel nanoarchitecture‐catalyst pairing, this work paves the way for decentralized, point‐of‐care diagnostics of emerging pathogens.