Acridine Orange Sensitization and DNA Inhibition Effects on the Cyclic Voltammetry of Naphthoquinones Using Bare and DNA Modified Gold Electrodes

Abstract

An ion pair mechanism is used to characterize the inhibition by DNA, and sensitization by acridine orange (AO) of the peak currents in the cyclic voltammetry (CV) of naphthoquinones with differing ionic substituents. Gold electrodes modified with adsorbed synthetic ′5-thiol-(GC)10 double strand DNA oligomers are used to study the redox activity of ferricyanide, 1,2-naphthoquinone-4-sulfonic acid sodium salt (NQS), 4-amino-1,2-naphthoquinone (ANQ), or 1,2-naphthoquinone (NQ) in the presence of AO. Parallel studies are performed using bare gold electrodes with double strand calf thymus DNA (CT-DNA) in the bulk solution. AO is known to bind intercalatively to DNA and is seen to sensitize the redox activity of ferricyanide or NQS with DNA either adsorbed on the electrode or present in the electrolyte. AO otherwise does not sensitize the peak currents in the CV of either ANQ or NQ regardless of the presence of DNA, nor does the DNA inhibit their CV, as it does the AO sensitized CV of the anions in the presence of DNA. The electroanalysis is done in pH 7 phosphate buffer with the solute and calf thymus double strand DNA base pair concentrations in the 10–3 molar range, and AO concentrations in the 10–4 molar range. The anion selective electrolytic sensitization combined with the intercalative property of AO may be applied to either the design of DNA based biosensors for the detection of anions, or DNA sensitive biosensors using AO as a marker.