Titanium-vanadium oxide nanocomposite based solid-state dual-electrode sensor for SARS-CoV-2 nucleic acid detection

COVID-19 outbreak, caused by the SARS-CoV-2 RNA virus, elevates the need for a rapid, reliable, inexpensive, and easily accessible disease diagnostic tool. The present go-to approach for SARS-CoV-2 RNA detection is the real-time reverse transcriptase polymerase chain reaction (RT-PCR) test which despite being the most reliable method has few drawbacks including being lengthy and laborious. Approaching the diagnosis from an electrochemistry pathway is a relatively economical, decentralized and yet highly sensitive route. This work aims to construct an electrochemical (bio)sensor with 2-electrode geometry with a transition metal oxide (TMO) based sensing layer. We have fabricated a series of TiO2-V2O5 (TVO) nanocomposites to probe their electrochemical performance and attain a highly sensitive dual-electrode electrochemical sensor (DEES) compared to the pristine V2O5. The XRD analysis of the electrodes confirmed the formation of nanocomposite while the XPS analysis correlated the formation of oxygen vacancies with improved electrical conduction measured via EIS and I-V characterization. The optimized electrode was then utilized to electrochemically detect end-point LAMP readout for 10^1 – 10^4 copies of plasmid DNA and in vitro transcribed SARS-CoV-2 RdRp RNA in an aqueous solution. Additionally, the DEES was also applied to detect in situ LAMP performed on SARS-CoV-2 plasmid and RNA magneto-extracted from a) aqueous solution; b) sample spiked with excess human genomic DNA, and c) a viral transport medium (VTM)-mimic sample. The DEES results were compared with real-time fluorescence and commercially available screen-printed electrodes (SPE). Our device was able to successfully detect magneto-extracted plasmid DNA and in vitro transcribed SARS-CoV-2 RNA to the limit of detection of 2.5 copies/μL.