Oxygen vacancy modulated MnO2 bi-electrode system for attomole-level pathogen nucleic acid sequence detection

Abstract

Electrochemical nucleic acid detection has recently opened a relatively low budget, straightforward and speedy approach of detection with the aid of an electrochemically active redox probe. However, electrochemical sensors of nucleic acid amplification characteristically employ a tri-electrode geometry involving standard reference electrode usually made up of a noble metal that adds up the cost of detection. This work proposes a sensitive and rapid approach for detecting the endpoint of nucleic acid amplification test using a novel bi-electrode sensing geometry. The sensing layer of the electrode was comprised of a transition metal oxide to tune its electronic state for regulating its electrochemical response. The XPS analysis indicates a higher contribution of Mn3+ oxidation state than Mn4+ when annealed at elevated temperature, suggesting the formation of oxygen vacancies into the sensing layer. The formation of oxygen vacancies improved the electrical conduction of the layer as evident from the significant reduction in charge transfer resistance (Rct) value from electrochemical impedance spectroscopy (EIS) measurements. The fabricated device was then used to detect dengue virus sequence DNA (using rolling circle amplification) and Staphylococcus aureus genomic DNA (using polymerase chain reaction) with the limit of detection in the order of 103 target DNA copies