Time-Multiplexed Organic Electrochemical Transistor for Saliva-Based Rapid Detection of Viral Proteins.

Timely and accurate diagnosis of respiratory infections is complicated by the symptomatic overlap between highly transmissible pathogens such as respiratory syncytial virus (RSV), influenza A (IAV), and influenza B (IBV), highlighting the need for rapid and reliable diagnostics. Here, we report a time-multiplexed nanobody-functionalized organic electrochemical transistor (OECT) biosensor for the sensitive detection of RSV, IAV, and IBV directly from unprocessed saliva samples. The platform integrates arrays of nanobody-functionalized gate electrodes that are exposed in parallel to a single sample and sequentially addressed through a shared transistor channel. We characterize nine previously reported nanobodies and immobilize the best-performing ones using an oriented SpyDirect self-assembly strategy. The nanobody-functionalized gate electrodes are paired with a high-performance p-type organic mixed ionic-electronic conductor channel, enabling efficient signal transduction. The sensor achieves a limit of detection of ca. 1 fm and identifies viral targets within 15 min, without sample preprocessing. In a clinical validation using 17 samples, the platform demonstrated 100% specificity, 86.7% sensitivity, and 88.2% overall accuracy. By combining highly specific nanobodies, a high-gain transducer, customized surface pre-treatment, and a time-multiplexed multi-gate architecture, this approach provides a scalable and user-friendly platform for point-of-care virus detection.