Fabrication of polythionine/NPAu/MWNTs modified electrode for simultaneous determination of adenine and guanine in DNA

In this work, a novel route for the fabrication of polythionine/gold nanoparticles/multi-wall carbon nanotubes (PTH/NPAu/MWNTs) modified electrode was proposed via a two-step process. First, the gold nanoparticles/multi-wall carbon nanotubes (NPAu/MWNTs) composites, which were synthesized by ultrasonic, were deposited on the glassy carbon electrode to prepare the NPAu/MWNTs electrode. Then, the thionine was electropolymerized on the surface of NPAu/MWNTs modified electrode to prepare the PTH/NPAu/MWNTs modified electrode. The performances of the PTH/NPAu/MWNTs modified electrode were characterized with cyclic voltammetry (CV) and transmission electron microscopy (TEM). The modified electrode exhibited enhanced electrocatalytic behavior and good stability for the detection of guanine and adenine in 0.1 M PBS (pH 7.0). The experimental parameters were optimized and a direct electrochemical method for the simultaneous determination of guanine and adenine was proposed. The detection limit (S/N = 3) for guanine and adenine was 1 × 10−8 M and 8 × 10−9 M, respectively. A sensitive electrochemical method for the measurement of guanine and adenine in calf thymus DNA was also developed with this modified electrode.