Capillary-Driven Duplex Microfluidic Device Enabling Simultaneous Electrochemical Immunoassays for Detecting SARS-CoV-2 and Respiratory Syncytial Virus.

This study aims to develop a rapid, multiplexed electrochemical sensor for the simultaneous detection of SARS-CoV-2 nucleocapsid protein and respiratory syncytial virus fusion protein for timely, accurate point-of-care (POC) diagnosis and differentiation between the two viral infections that result in similar symptoms and could pose serious complications in vulnerable populations. The system utilizes duplex electrochemical capillary-driven immunoassay (eCaDI) devices that combine the sensitivity and quantifiability of electrochemical sensing with the simplicity, which eliminates the need for an active pump, and the automation feature of capillary-driven microfluidics. The duplex eCaDI integrates near-field communication-powered electrochemical detection into a dual-channel capillary-driven microfluidic design for improved portability and applicability in POC settings. The duplex eCaDI achieved limits of detection of 1.5 ng/mL for nucleocapsid protein and 7.9 ng/mL for fusion protein, with a total assay time of 6 min. Moreover, pooled nasal swab samples from healthy donors were spiked with low (50 ng/mL), medium (200 ng/mL), and high (500 ng/mL) concentrations of target proteins and were tested with the duplex eCaDI, showing 100% detection rate in high and medium concentration samples and 50% in low concentration samples. This system can further be integrated with a smartphone-based program to immediately provide intuitive results to end users, suggesting a promising solution to achieve rapid, power-efficient, and user-friendly multiplexed diagnosis of respiratory viruses across various environments.