Researchers Develop Accurate, High-Speed, Portable Bi-Functional Electrical Detector for COVID-19

The unique feature of this method is that the extent of hybridization between the ss-DNA probe and viral RNA can be directly converted to the current change of graphene channels without repetition of the PCR process, thus affording an ultra-low limit of detection (LOD) of 0.1 fg/mL for the detection of the RNA-dependent RNA polymerase (RdRp) gene target of SARS-CoV-2.

Furthermore, this method was validated using clinical samples collected from many patients with COVID-19 infection and healthy individuals as well, and the testing results were in full agreement with those of PCR-based optical methods. The entire process, precluding the extraction of detection targets from oropharyngeal swabs, requires approximately 10 min. Because it does not involve time-consuming PCR step nor expensive instruments, this detection system enables massive point-of-care testing of COVID-19, outside of specialized diagnostic laboratories, with the advantage of high accuracy, sensitivity and low cost.

Notably, false negative results are inevitable in the course of nucleic acid testing; thus, the use of immunodetection as an auxiliary technique is important in the diagnosis of COVID-19 patients, especially those with suspected diseases. By replacing the ss-DNA probe with a SARS-CoV-2 antigen protein, this detection system can also detect SARS-CoV-2 IgM and IgG antibodies with an ultra-low LOD of 1 fg/mL. Immunoassays of serum specimens of COVID-19 patients and healthy subjects matched excellently with those of PCR-based optical methods.

This detecting system exhibits obvious advantages of high sensitivity, rapid speed (10 min for RNA analysis and 5 min for immunoassay), and bifunction (both RNA analysis and immunoassay). These advantages enable high-throughput point-of-care testing, which may facilitate management of the current severe public health crisis. Furthermore, this detection system offers a universal methodology that is ready for immediate application in rapid detection of novel viruses in future.

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