Adsorption of DNA Probe on Carbon Electrode

The DNA-probe immobilized electrode was prepared for a “DNA sensor”, which is our original electrochemical gene detection method. We devised the DNA sensor by the adsorption of synthesized oligonucleotides on a basal plane pyrolytic graphite (BPPG) electrode. Thus, we examined the adsorptive characteristics of oligouncleotides, because we had little knowledge about their adsorptive behavior. The oligonucleotides electrochemically showed two irreversible anodic waves due to oxidation of guanine and adenine residues. We estimated the quantity of oligonucleotides on the electrode by measuring the anodic current. The desorption of oligonucleotides from the electrode was not observed by applying a negative potential or washing the electrode. The quantity of adsorbed oligonucleotides increased with temperature. These data imply that oligonucleotides are adsorbed on the electrode through chemisorption. Furthermore, the adsorptive characteristics of monomers (2′-deoxyguanosine and 2′-deoxyguanosine-5′-monophosphate), a dimer (5′-GpG-3′), and a trimer (5′-GpGpG-3′) of guanine residues snggest that phosphate groups and chain lengths of oligonucleotides may play important roles in the adsorption of oligonucleotides on the electrode.