A simple approach for DNA detection on carbon nanotube microelectrode arrays

We present a simple approach for DNA detection which profits from the use of miniaturized carbon nanotube (CNT) electrodes, Ru(NH ₃) ₆ ^2+/3+ as redox DNA hybridization reporters and sensitive but simple electrochemical techniques (chronocoulometry and impedance spectroscopy). The manufacturing process employed in this work yielded robust, highly controlled and well-defined microelectrode arrays of vertically aligned multi-walled CNTs which facilitated very reproducible electroanalytical measurements. The hybridization process and its efficiency were monitored and quantified with chronocoulometric measurements by following up the Ru(NH ₃) ₆ ^2+/3+ adsorption at the DNA phosphate backbone. Limits of detection of 1 nM and an efficiency of nearly 100% were found with such methodology. One of the advantages of using CNT microelectrodes is that the scaling down of the electrode size allows the impedimetric detection with such highly positively charged redox reporters, using the charge transfer resistance as an indicator of the DNA hybridization. Such detection scheme would not have been possible in macroscopic CNT electrodes due to the dominance of the diffusion controlled processes. Limits of detection of 100 pM were achieved using the impedimetric technique. The combination of the miniaturized and robust CNT-based electrodes, the advantages of the chosen redox reporter and the electrochemical techniques provide a very simple, reproducible and efficient strategy that could facilitate genosensing and diagnosis.