Electrochemical signal amplification for pathogen nucleic acid detection utilizing a cobalt-based DNA-binding metallo-intercalator†

This paper reports the development of a highly sensitive and rapid electrochemical biosensor for the detection of pathogen nucleic acids. The primary objective was to enhance the detection sensitivity of DNA biosensors for pathogen nucleic acids commonly found in fresh and wastewaters, the food industry, and clinical samples. This enhanced sensitivity was achieved through the addition of a [Co(GA)₂(aqphen)]Cl intercalating complex to increase the electrostatic field at the sensor surface/solution interface. Voltammetric and impedance-based detection techniques were employed to characterize the intercalation and redox-active properties of the compound. Additionally, non-faradaic impedance and voltammetric methods were characterized as appropriate techniques for electrochemical detection. Implementing the [Co(GA)₂(aqphen)]Cl intercalator led to increased voltammetric signal output using DPV, facilitating the rapid and sensitive detection of target DNA sequences. Notably, the [Co(GA)₂(aqphen)]Cl permitted detection using non-faradaic impedance in the absence of [Fe(CN)₆]^3−/4−. Characterization by cyclic voltammetric measurements revealed a surface-controlled redox mechanism and reversible electrochemistry of the compound intercalated with double-stranded DNA (dsDNA). Upon binding of 1 μM target DNA and 200 μM [Co(GA)₂(aqphen)]Cl, a 2250% current peak increase was achieved. This increase enabled the sensitive detection of a target DNA sequence representative of E. coli DNA in buffer with an LOD of 67.5 pM, 100-fold more sensitive than the standard unlabeled assay while maintaining assay simplicity, low cost, and quick response. The use of [Co(GA)₂(aqphen)]Cl among similar compounds in DNA biosensors offers a cost-effective and sensitive method for detecting waterborne pathogens such as E. coli. This approach could significantly improve environmental monitoring and pollution control by enabling more reliable and rapid monitoring of pathogens in water sources. Additionally, it has the potential to be of great use within the food industry and in point-of-care clinical settings.