DNA-Mediated Fluctuations in Ionic Current through Silicon Oxide Nanopore Channels

Single molecule sensors in which nanoscale pores within biological or artificial membranes act as mechanical gating elements are very promising devices for the rapid characterization and sequencing of nucleic acid molecules. The two terminal electrical measurements of translocation of polymers through single ion channels and that of ssDNA molecules through protein channels have been demonstrated, and have sparked tremendous interest in such single molecule sensors. The prevailing view regarding the nanopore sensors is that there exists no electrical interaction between the nanopore and the translocating molecule, and that all nanopore sensors reported to-date, whether biological or artificial, operate as a coulter-counter, i.e., the ionic current measured across the pore decreases (is mechanically blocked) when the DNA molecule transverses through the pore. We have fabricated nanopore “channel ” sensors with a silicon oxide inner surface, and our results challenge the prevailing view of exclusive mechanical interaction during the translocation of dsDNA molecules through these channels. We demonstrate that the ionic current can actually increase due to electrical gating of surface current in the channel due to the charge on the DNA itself. As a first step toward the ultimate goal of single-molecule DNA sequencing using nanopore sensors, one must first identify the key mechanical and electrical variables that control the translocation of the molecules through th