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

Paper DN+BI-MoA10
Ion Current Detection of Mono-nucleotide Passing into a Nano-hole Fabricated on Si Wafer

Monday, October 31, 2005, 5:00 pm, Room 311

Session: DNA Detection and Sensing
Presenter: A. Oki, National Institute for Materials Science, Japan
Authors: A. Oki, National Institute for Materials Science, Japan
Y. Horiike, National Institute for Materials Science, Japan
Correspondent: Click to Email
D. Branton et al. demonstrated the electrical sequencing based on measurement of currents generated by passage of single-strand DNA into a 2 nm hole drilled in a cell membrane. But about 5 nm thick membranes do not allow discriminating single molecule of DNA with stacking spacing of 0.34 nm. For the goal, we have studied detection of currents generated from one base flowing into the nano-hole after cutting DNA to each base using a reaction of @lambda@exonuclease. The nano-hole was fabricated as follows: First, the KOH etching fabricated an anisotropic feature on the backside of the wafer through a 44 µm square Si@sub 3@N@sub 4@ mask, thus self-stopping at 31 µm depth. Then, the KOH etching opened an anisotropic feature on the upper side masked by a 5 mm square window, thereby forming a 360 nm diameter hole on the bottom of the upper side. 50 nm thick SiO@sub 2@ film grown on Si and subsequent CVD of 150 nm thick Si@sub 3@N@sub 4@ film filled periphery of the hole. Finally, 4.5 KeV Ar@super +@ ion irradiation removed the Si@sub 3@N@sub 4@ film on the hole position, thus fabricating the nano-size hole by monitoring instant increase of the ion current using a micro-channel plate set under the wafer. The hole size was not observed by SEM. To measure ion currents generated by mono-nucleotide passing the nano-hole, each 500 µM natural mono-nucleotide of dGMP, dCMP, dAMP, TMP was solved in a TE buffer solution, where a pair of a KCl saturated calomel was used as electrodes. Each ion current increased with increasing voltage. At 1.5V, ion currents of dCMP, TMP, dGMP, and dAMP were 45.9, 21.5, 15.5 and 13.8 nA, respectively. If the ion current varied inversely with molecular weight of mono-nucleotide, increases in order of ion currents are understood for dCMP and TMP. However present experimental accuracy must be checked for inverse characteristic of dGMP for dAMP because of small difference between both ion currents.