AVS 52nd International Symposium
    DNA Topical Conference Monday Sessions
       Session DN+BI-MoA

Paper DN+BI-MoA6
DNA Conductance Sensor Platforms Using Nano-scale Break Junctions

Monday, October 31, 2005, 3:40 pm, Room 311

Session: DNA Detection and Sensing
Presenter: A.K. Mahapatro, Purdue University
Authors: A.K. Mahapatro, Purdue University
K.J. Jeong, Purdue University
S. Bhattacharya, Purdue University
G.U. Lee, Purdue University
D.B. Janes, Purdue University
Correspondent: Click to Email
For DNA sensors, a direct electrical readout of DNA selective binding events would enable integration of sensor elements with readout circuits. A possible readout approach involves measurement of the electrical conductivity of DNA strands bridging two narrowly spaced metallic contacts. In this work we describe few-molecule conductance measurements with electromigration-induced break-junctions (EIBJ). The double-stranded(ds) DNA oligionucleotide sequences are GGCGCGCGGGCGGGC-(CH@sub2@)@sub3@-SH-3', GGCGCAAAAACGGGC-(CH@sub2@)@sub3@-SH-3', and HS-(CH@sub2@)@sub6@-CGGAGAGTTGAGCAT-3', and their complements. Lithographically defined Au wires are formed by e-beam evaporation over oxidized silicon substrates silanated with (3-Mercaptopropyl)trimethoxysilane (MPTMS), then subjected to electromigration at room temperature to create nano-gaps. Although the Au wires are initially 2µm wide, gaps with length ~1nm and width ~5nm are observed after breaking, as observed through a field effect scanning electron microscope. ds-DNA was immobilized on the electrodes by assembling the DNA double-strands in an aqueous solution, reacting these solutions with the electrodes in solution, locking the double-helix configuration with a polycation, thorough rinsing with ultrapure water to remove any residual salt, and drying before measurement. The GC-rich, 3' thiol labeled DNA showed approximately 1Gohm resistance, but little conductivity was measured in the AT-rich or 5'thiol labeled DNA. This is consistent with single molecule conduction measurements where enhanced conductivity has been observed in GC-rich DNA. For the GC-rich DNA, higher conductivity is observed for devices immobilized in a higher concentration of salt (NaCl) in the standard phosphate buffer solution, which is attributed to more DNA-molecules immobilized between the electrodes. This study demonstrates that the EIBJ technique can be used to understand the electrical properties in nanometer scale materials such as DNA.