A brief note on the potential of homo-oligo-dsDNA and hetero-oligo-dsDNA based on their binder-free electrochemical characteristics on gold electrode

Abstract

In this fundamental research, we found that homo-oligo based dsDNA holds potential electrochemical characteristics in comparison to hetero-oligo based dsDNA which can be exploited in voltammetric and impedimetric biosensors. We prepared a homo-oligo based dsDNA from 20 deoxyribonucleotides of adenine, guanine, cytosine, and thymine (A20, G20, C20, and T20 respectively) and a hetero-oligo based dsDNA from two partially complementary oligos (5'-TTT TTT CAT CTA TCA ACA TCA GTC TGA TAA GCT ATA GAA GC-3' and 5'-TTT TTT ATA GCT TTG ATA GA-3'. Electrochemical impedance spectroscopy in 1 mM 0.1 M K₃[Fe(CN)₆]/KCl showed that Au working electrode modified with hetero-oligo based dsDNA (Au/hetero-oligo-dsDNA) was more resistive toward charge transfer of Fe(CN)₆^3-/4- compared to Au working electrode modified with homo-oligo based dsDNA (Au/homo-oligo-dsDNA). Additionally, cyclic voltammetry and linear sweep voltammetry showed that Au/homo-oligo-dsDNA produced quantifiable anodic and cathodic peak currents which were not observed for Au/hetero-oligo-dsDNA. Nyquist and Bode plots derived from electrochemical impedance spectroscopy on three different electroactive areas (0.0705, 0.0747 and 0.0837 cm²) of Au working electrode showed no significant change in the capacitive behavior of Au/homo-oligo-dsDNA and Au/hetero-oligo-dsDNA in a linear range of frequency (10-100 Hz).

Keywords: Deoxyribonucleic acid; Electrochemistry; Hetero-oligo; Homo-oligo; Impedance.