Direct DNA hybridization detection based on the oligonucleotide-functionalized conductive polymer

Electrochemical methods for DNA hybridization detection have many advantage s that are very fast to detect hybridization and can be directly applied fo r a portable DNA sensor. In this paper, an electrochemical method to direct ly detect DNA hybridization was developed on the basis of a new conductive polymer, which was polymerized on the glassy carbon electrode with a terthi ophene monomer having a carboxyl group (3'-carboxyl-5,2',5',2"-terthiophene ). The ss-DNA probe was made by chemically bonding an amine-linked C-6 alky l group to the 5' terminus of oligonucleotide (19-mer). The probe moiety wa s immobilized on the polymer through covalent bonding with a catalyst, 1-et hyl-3-(3-dimethylaminopropyl)carbodiimide. A difference in admittance was o bserved before and after hybridization as a result of the reduction of the resistance after hybridization. The highest difference in admittance was ob served around 1 kHz before and after hybridization. Hybridization amounts o f end two-base and center one-base mismatched sequences were obtained only in a 14.3% response when compared to that for the complementary matched seq uence.