We report an electrical scheme to detect specific DNA. Engineered hairpin probe DNA are immobilized on a silicon chip between gold nanoelectrodes. Hybridization of target DNA to the hairpin melts the stem nucleotides. Gold nanoparticle-conjugated universal reporter sequence detects the open hairpins by annealing to the exposed stem nucleotides. The gold nanoparticles increase charge conduction between the electrodes. Specifically, we report on a hairpin probe designed to detect a medically relevant mutant form of the K-ras oncogene. Direct current measurements show three orders of magnitude increase in conductivity for as low as 2fmol of target molecules.

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