Voltammetric determination of sequence-specific DNA by electroactive intercalator on graphite electrode

A synthesized 24-mer single-stranded deoxyribonucleic acid (ssDNA) was covalently immobilized onto a chemically-modified graphite electrode with surface-bound primary amino groups, using water-soluble 1-ethyl-3-(3-dimethylaminopropyl)-carbodiimide (EDC). The immobilized ssDNA was hybridized with various concentrations of complementary DNA (cDNA) in hybridization buffer solution containing ethidium bromide (EB). The dsDNA/EB system was formed on the electrode surface. The anodic waves of the EB bound to the double-stranded DNA (dsDNA) in cyclic voltammetry were used for the determination of cDNA. The anodic peak currents (ipa) of EB were linearly related to the concentrations of cDNA between 1 × 10−4mg ml−1 and 1 × 10−6mg ml−1. The detection limit was about 2 × 10−7mg ml−1.