Highly selective, reusable electrochemical impedimetric DNA sensors based on carbon nanotube/polymer composite electrode without surface modification.

We fabricated a composite of multi-walled carbon nanotube and polydimethylsiloxane and utilized it as an electrode for DNA sensing using electrochemical impedance spectroscopy. Without any surface modification or probe immobilization, often necessary for other electrodes, this electrode also acts as a recognition layer for DNA via π-π interactions between the multi-walled carbon nanotube and DNA. This electrode is easily reusable via a simple cleansing process, because there are no covalently bonded adsorbates on the electrode. Compared to previous DNA detection based on differential pulse voltammetry using a similar electrode, the measurement time was reduced from 1 h to less than 30 min, and the limit of detection (25 pM) was reduced by a factor of more than five. In addition, our system can detect the single-base mismatch between the target and probe. Our results indicate that electrochemical impedance spectroscopy is promising for utilizing the multi-walled carbon nanotube and polydimethylsiloxane electrode as a DNA sensor.