Watching DNA Charge Ahead

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Science  20 Jan 2012:
Vol. 335, Issue 6066, pp. 265
DOI: 10.1126/science.335.6066.265-b

A prospective alternative approach to direct DNA sequencing is to monitor changes in ion current as a DNA strand translocates through a nanopore. However, the speed of the translocation process—about 1 base per microsecond—exceeds the response speed of the electronics needed to amplify the small changes in current when measured with microelectrodes in solution. A field-effect transistor (FET) close to the pore should have sufficient speed and sensitivity to resolve these signals, but charge signals might be screened by the high ionic strength of the solvent. Xie et al. fabricated a silicon nanowire FET with a very short channel length (200 nm) on a silicon nitride membrane. They then etched a nanopore (7 to 10 nm in diameter) through the membrane and along the edge of the nanowire, and measured ion currents and FET signals for translocation of 2.6-kbp double-stranded DNA in 1 M KCl. The signal from the nanowire FET tracked that of the ion current measurement if a hundredfold dilution (10 mM KCl) was used in the receiving solution. Measurement of base-pair changes for single-stranded DNA will require further improvements in signal-to-noise ratio and spatial resolution.

Nat. Nanotechnol. 10.1038/nnano.2011.217 (2011).

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