MOLECULAR WIRING TYPE DNA SENSOR

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Electrochemical detection of specific DNA sequence of human papiroma virus was investigated using the gold electrode immobilized with probe DNA through a thiol group and tris(1,10-phenanthroline) cobalt (II) complex [Co(phen)_3^<2+>] as a hybridization indicator.25-mer probe DNA modified with a thiol group at 5' end was immobilized on a gold electrode. Tris(1,10-phenanthroline) cobalt (II) chloride was prepared according to previously reported procedure. The gold electrode immobilized with probe DNA was immersed into buffer solution (pH 7.0) containing target DNA.Hybridization reaction was performed for an hour at 65 C。.After the hybridization, the electrode was immersed into Co(phen)_3^<2+>/0.1M phosphate buffer (pH 7.0). Cyclic voltammetry was performed in Co(phen)_3^<2+>/0.1 M phosphate buffer (pH 7.0).Anodic peak current of cyclic voltammograms of 0.1 mM Co(phen)_3^<2+>/0.1 M phosphate buffer (pH 7.0) using the probe DNA-modified gold electrode hybridized with target DNA was larger … More than that using the probe DNA-modified gold electrode.When the concentration of Co(phen)_3^<2+> was 0.1 mM, the response currents depended on target DNA concentration. However, at another Co(phen)_3^<2+> concentrations of 0.2 mM, 0.3mM and 1.0 mM examined, the response currents did not clearly depend on target DNA concentration.The response currents were linearly related to target DNA concentration in the range from 10^<-7> M to 10^<-4> M with a slope of 10.5 nA / decade. Similar measurement was performed using the probe DNA-modified gold electrode reacted with 25-mer poly-deoxy A as non-complementary DNA.The response currents were hardly increased in the same range. On the other hand, all currents were slightly decreased from that using probe DNA-modified electrode. It seems that the surface of DNA-modified electrode suffer from chemical alteration because the electrode was repeatedly used increasing the concentration of target DNA (or poly-deoxy A) after one measurement. From these results, it was shown that a certain sequence of DNA, which is complementary to probe DNA, can be detected using cobalt phenanthroline complex and probe DNA-modified gold electrode. Less