Electrochemical DNA Sensor Based on Poly(Azure A) Obtained from the Buffer Saturated with Chloroform

Electropolymerized redox polymers offer broad opportunities in detection of biospecific interactions of DNA. In this work, Azure A was electrochemically polymerized by multiple cycling of the potential in phosphate buffer saturated with chloroform and applied for discrimination of the DNA damage. The influence of organic solvent on electrochemical properties of the coating was quantified and conditions for implementation of DNA in the growing polymer film were assessed using cyclic voltammetry, quartz crystal microbalance, and electrochemical impedance spectroscopy. As shown, both chloroform and DNA affected the morphology of the polymer surface and electropolymerization efficiency. The electrochemical DNA sensor developed made it possible to distinguish native and thermally and chemically damaged DNA by changes in the charge transfer resistance and capacitance.

Multi-walled Carbon Nanotubes/Manganese Dioxide Nano- flowers-like/Polyaniline Nanowires Nanocomposite Modified Electrode: A New Platform for a Highly Sensitive Electrochemical Impedance DNA Sensor

We describe in this report a development of label-free electrochemical DNA sensor based on a novel nanostructured electrode of multi-walled carbon nanotubes (MWCNTs)/ nano-flowers-like manganese dioxide (MnO2)/polyaniline nanowires (PANi NWs) nanocomposite. The nanocomposite was synthesized in-situ onto an interdigitated platinum microelectrode (Pt) using a combination of chemical and electrochemical synthesis methods: chemical preparation of MWCNTs/MnO2 and electropolymerization of PANi NWs. The fabricated MWCNTs/MnO2/PANi NWs was then used to develop a label-free electrochemical DNA sensor for a specific gene of Escherichia coli (E.coli) O157:H7 detection. The MWCNTs/MnO2/PANi NWs modified Pt electrode’s surface can facilitate for probe DNA strands immobilization and, therefore the electrochemical signal of the DNA sensors has been improved. The electrochemical impedance spectroscopy (EIS) measurements were conducted to investigate the output signals generated by the specific binding of probe and target DNA sequences. Obtained results indicated that the developed electrochemical biosensor can detect the target DNA in the linear range of 5 pM to 500 nM with a low limit of detection (LOD) at 4.42 × 10 –13 M. The research results demonstrated that the MWCNTs/MnO2/PANi NWs nanocomposite-based electrochemical DNA sensor has a great potential application to the development of highly sensitive and selective electrochemical DNA sensors to detect pathogenic agents.