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 d sDNA/EB system was formed on the electrode surface. The anodic waves o f the EB bound to the double-stranded DNA (dsDNA) in cyclic voltammetr y were used for the determination of cDNA. The anodic peak currents (i (pa)) of EB were linearly related to the concentrations of cDNA betwee n 1 x 10(-4) mg ml(-1) and 1 x 10(-6) mg ml(-1). The detection limit w as about 2 x 10(-7) mg ml(-1).