Patent ID: 7169556

Claim:
An isothermal method for detecting a nucleic acid having at least two portions, the method comprising: (a) contacting a nucleic acid with a substrate having oligonucleotides attached thereto, the oligonucleotides being located between a pair of electrodes, the oligonucleotides having a sequence complementary to a first portion of the sequence of said nucleic acid, the contacting taking place under conditions effective to allow hybridization of the oligonucleotides on the substrate with said nucleic acid; (b) contacting said nucleic acid bound to the substrate with a first type of nanoparticles, the nanoparticles being made of a material which can conduct electricity, the nanoparticles having one or more types of oligonucleotides attached thereto, at least one of the types of oligonucleotides having a sequence complementary to a second portion of the sequence of said nucleic acid, the contacting taking place under conditions effective to allow hybridization of the oligonucleotides on the nanoparticles with said nucleic acid so as to form a test substrate having nanoparticles complexed thereto; (c) contacting the test substrate with an aqueous salt solution having a salt concentration effective to sufficiently dehybridize and remove non-specifically bound nanoparticles, said contacting the test substrate occurring without temperature elevation; and (d) detecting for the presence or absence of the nucleic acid by observing for any detectable change in an electrical property between the electrodes resulting from the presence of specifically bound nanoparticles.