title: Electrochemical sensor for detection of unmodified nucleic acids.
abstract: We have developed a nucleic acid (NA) sensor based on mediated electrochemical oxidation of guanine residues. In this method, oligonucleotide probes are bound to a tin-doped indium oxide (ITO) electrode through a self-assembled phosphonate monolayer. The end carboxyl moiety of the monolayer is activated with carbodiimide and reacted with the amine group of a C6 alkyl linker which has been added to the 5'-end of the oligonucleotide probe. Upon hybridization of the complementary target NA, the hybrid is detected using a redox-active mediator, tris(2,2'-bipyridyl) ruthenium(II). We speculate that the monolayer does not impede electron-transfer since it contains many defect sites when assembled on a polycrystalline ITO surface. These defect sites are accessible to the mediator, but not to NA or proteins. The electrocatalytic current was a linear function of the amount of guanine bound at the electrode surface, with a detection limit of 120 amoles of guanine cm(-2) at 0.28 cm(2) ITO electrodes.
authors.affiliation: Xanthon, Inc., 104 T.W. Alexander Drive, P.O. Box 12296, Research Triangle Park, NC 27709, USA.
authors.forename: N D
authors.initials: ND
authors.lastname: Popovich
authors.forename: A E
authors.initials: AE
authors.lastname: Eckhardt
authors.forename: J C
authors.initials: JC
authors.lastname: Mikulecky
authors.forename: M E
authors.initials: ME
authors.lastname: Napier
authors.forename: R S
authors.initials: RS
authors.lastname: Thomas