A novel cobalt complex for enhancing amperometric and impedimetric DNA detection

In this work we present a novel cobalt complex, [Co(GA)2(aqphen)]Cl that is water-soluble, redox-active and binds to dsDNA. We report that this complex can be used as a signal enhancer when detecting DNA hybridisation using electrochemical impedance spectroscopy (EIS) and differential pulse voltammetry (DPV). The compound mediates its EIS signal enhancement by causing an increase in charge transfer resistance (Rct) when bound to dsDNA. Increased peak currents are also observed with DPV when the compound is incubated with dsDNA as compared with ssDNA. We believe that this compound intercalates specifically with dsDNA and alters the DNA structure to affect the electrostatic barrier to charged redox markers in solution. To our knowledge this is the first example of a single compound that can enhance both amperometric and impedimetric signals for DNA detection. Our findings enable the development of a label-free and multi-modal approach to improve the sensitivity, accuracy and speed of electrochemical DNA detection.