Ethylendiamine-functionalized multi-walled carbon nanotubes prevent cationic dispersant use in the electrochemical detection of dsDNA

Abstract

In this paper, for the first time, an electro-analytical method based on the direct adsorption of double-stranded deoxyribonucleic acid (dsDNA) at glassy carbon electrode modified with ethylendiamine (eda)functionalized multi-walled carbon nanotubes (eda-CNT) is reported. The carbon nanotubes were func-tionalized with ethylendiamine via chemical modification of the carboxyl groups, and the eda-CNTs werecharacterized by different techniques, including Fourier transform infrared (FT-IR) spectroscopy, thermogravimetric analysis (TGA), elemental analysis and cyclic voltammetry, and compared with pristine (CNT)and oxidized (ox-CNT) MWCNTs.The presence of eda on the CNT surface allows them to disperse in a phosphate buffer solution at pH7.0 and provides an environment that promotes the electrostatic adsorption of dsDNA. At eda-CNTs, theadsorption of dsDNA is improved and a linear correlation between the oxidation current of guanine basesand the accumulation time is observed. This result indicates that the presence of positive charges on thesurface of the nanotube plays an important role in the attraction of the dsDNA molecule.A more sensitive detection of DNA was obtained compared with CNT and ox-CNT when eda-CNTwhere used with a linear range from 5 to 60 ppm, a sensitivity of 0.0315 ± 0.0003 A mg–1L and a LODof 0.971 ppm after a 10-min accumulation which is lower than that obtained previously using cationicdispersing agents. The analytical performance reported is comparable with that reported previously forcationic polymers in terms of linear range and LOD values.