Direct electrochemistry of thermally denatured calf thymus DNA on a poly(methyl methacrylate)–graphite microcomposite electrode

Abstract

Remarkable direct electrochemical behaviors of thermally denatured calf thymus DNA (ssDNA) on the poly(methyl methacrylate)–graphite powder microcomposite electrode (PMMA/GME) were observed and investigated. The result indicated that the PMMA/GME showed great promotion of the electrochemical response towards the ssDNA oxidation due to the specific characteristics of the nanostructured interface on the resultant composite electrode. Two irreversible oxidation peaks at +1.04 and +0.76 V with obvious negative movement of oxidation potential and increase of the oxidation current (vs. Ag/AgCl) were observed on the PMMA/GME, which corresponded to the oxidation of adenine and guanine residues in the ssDNA molecules. Therefore, detection of ssDNA was then performed at the PMMA/GME. Under the optimal conditions, a good linear relationship was obtained between the oxidation peak currents of guanine or adenine residues and the ssDNA concentration in the range of 5.9 × 10⁻³ to ca. 1.1 mg mL⁻¹ with a detection limit of 1.0 μg mL⁻¹. This PMMA/GME exhibits some outstanding advantages, such as ease of fabrication, high stability, renewable surface, excellent stability, mechanical rigidity and high electrochemical reactivity, which holds huge promise for further DNA biosensor design.