A batch processed titanium-vanadium oxide nanocomposite based solid-state electrochemical sensor for zeptomolar nucleic acid detection.

Approaching a nucleic acid amplification test (NAAT) based diagnosis of a pathogen from an electrochemistry pathway is a relatively economical, decentralized, and yet highly sensitive route. This work aimed to construct an electrochemical biosensor with a 2-electrode geometry using a transition metal oxide (TMO) based sensing layer. A series of batch-processed TiO-VO (TVO) nanocomposite-based electrodes were fabricated to probe their electrochemical performance and attain a highly sensitive dual-electrode electrochemical sensor (DEES) compared to pristine VO. The XRD analysis of the electrodes confirmed the formation of a nanocomposite, while the XPS analysis correlated the formation of oxygen vacancies with improved electrical conduction measured EIS and - characterization. Furthermore, the work demonstrated the application of the optimized electrode in electrochemical detection of end-point loop-mediated isothermal amplification (LAMP) readout for 10-10 copies (0.1 zeptomoles to 0.1 attomoles) of SARS-CoV-2 RNA dependent RNA polymerase (RdRp) plasmid DNA and transcribed RNA in an aqueous solution. The device achieved a limit of detection as low as 2.5 and 0.25 copies per μL for plasmid DNA and transcribed RNA, respectively. The DEES was able to successfully detect LAMP performed on magneto-extracted SARS-CoV-2 plasmid and RNA from (a) an aqueous solution, (b) a sample spiked with excess human genomic DNA, and (c) a serum-spiked sample. The DEES results were then compared with those of real-time fluorescence and commercially available screen-printed electrodes (SPEs).