Small Molecule‐Driven Organic Electrochemical Transistors for Rapid, Ultrasensitive and Amplification‐Free Detection of RNA Biomarkers

RNA biomarkers are vital for diagnosing infections, cancer, and neurodegenerative diseases. RT-qPCR is sensitive but complex and equipment-intensive, limiting point-of-care use. Herein, for the first time, an organic electrochemical transistor (OECT) biosensor is reported utilizing small molecules as recognition elements for rapid, ultrasensitive and amplification-free detection of RNA. The biosensor leverages "click chemistry" to precisely immobilize screened and chemically edited small molecules to the OECT gate, enabling efficient target RNA binding. To further enhance sensitivity and reduce detection time, a rapid sample incubation module utilizing alternating current (AC) electrokinetic acceleration without the influence of electric currents and thermal effects strategy is employed to accelerate biomolecule transport and increase binding kinetics. This approach is validated using a model system incorporating C5, a chemically optimized small-molecule ligand that selectively binds SARS-CoV-2 RNA. The resulting biosensor achieves real-time, amplification-free RNA detection within three minutes, and the results are transmitted to electronic devices via Bluetooth. Notably, it shows impressive sensitivity (0.3 aM) and excellent long-term stability, retaining functional sensitivity for five months under ambient storage. This work establishes a new paradigm for RNA biosensing, demonstrating the power of integrating small-molecule recognition, electrochemical transduction and AC field enhancement for next-generation rapid diagnostics.