Electrochemical genomagnetic assay for detection of SARS-CoV-2 RNA using a disposable microfluidic platform

The COVID-19 pandemic exposed the world to one of the greatest challenges in our history, causing profound social and economic impacts. With the advance of the pandemic, it became evident that there was a need for new diagnostic tests for monitoring and controlling the disease. In this sense, we describe the development of a genomagnetic assay based on the use of a fully disposable electrochemical microfluidic device for detection of RNA from severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) in saliva samples.

A simple and low-cost disposable microfluidic platform (DmicroP) containing unmodified carbon-based electrodes was developed and coupled to a 3D holder containing neodymium magnets for detection of SARS-CoV-2 RNA in saliva samples. The device allows up to 8 simultaneous detections using the genomemagnetic assay, providing sensitivity with a limit of detection of 0.44 fmol L^-1 and a limit of quantification of 1.44 fmol L^-1, with a linear range of 5.0 fmol L^-1 to 200.0 nmol L^-1. The proposed assay has been successfully applied for the diagnosis of COVID-19 in cohorts of positive and negative individuals, showing excellent agreement with the results obtained by reverse transcription-polymerase chain reaction (RT-PCR). The genomagnectic assay showed the ability to discriminate between healthy individuals and patients infected with SARS-CoV-2, showing 82.4 % and 100.0 % of clinical sensitivity and specificity, respectively.

The method developed allows a simple, low-cost, and quantitative detection of viral RNA requiring no transcription or DNA amplification steps showing excellent reproducibility. The genomagnetic assay proposed can be an alternative tool for the diagnosis and monitoring of COVID-19 and even could be easily adapted for detection of other single-stranded RNA viruses.