A simple label-free electrochemical DNA biosensor based on carbon nanotube–DNA interaction

Abstract

A simple platform based on a hairpin oligonucleotide switch and multi-walled carbon nanotubes (MWCNTs) for the ultrasensitive detection of specific DNA sequences has been developed. In this approach, the π-stacking interaction of single-strand DNA–MWCNT was employed to construct an electrochemical DNA biosensor. Changes to the surface conductivity, based on the MWCNT replacement, were monitored by using the electrochemical species [Fe(CN)₆]^3−/4− as a redox probe. Morphological and voltammetric characterizations of the electrode surface were performed using atomic force microscopy (AFM), energy dispersive spectroscopy (EDS), cyclic voltammetry (CV), differential pulse voltammetry (DPV) and electrochemical impedance spectroscopy (EIS) techniques. This biosensor has a good linear correlation range, from 0.1 μM to 10 pM, for the model target DNA. This approach provides a precise method for the sensitive detection of sequence-specific, non-complementary and mismatched DNA with significant advantages in terms of simplicity, low cost, and stability.