Voltammetric Behavior and Detection of DNA at Electrochemically Pretreated Glassy Carbon Electrode

Abstract

Electrochemical oxidation of thermally denatured DNA at an electrochemically pretreated glassy carbon electrode was studied by means of adsorptive stripping voltammetry. The sensitivity for thermally denatured DNA detection at GCE was improved greatly by modifying the electrode with a simple and effective electrochemical oxidation at +1.75 V (vs. SCE) for 300 s in pH 5.0 phosphate buffer. Thermally denatured DNA was preconcentrated at pretreated GCE by its adsorption in open circuit for 5 min or at the potential of +0.3 V for 90 s, and produced two well-defined oxidation peaks of guanine and adenine residues at +0.80 V and +1.11 V in pH 5.0 phosphate buffer, respectively, while the native DNA almost did not appear at the same condition. This adsorptive stripping method can be used to study the properties of DNA using simple CV technique. A convenient quantitation of the low level of thermally denatured DNA was proposed. The detection limit of thermally denatured DNA was ca. 2.0 μg mL−1 when the accumulation time is 150 s at the potential of +0.3 V. As comparison, the acid-denatured DNA (treated in HClO4 solution) was tested at the same condition and a detection limit of 0.10 μg mL−1 was obtained.