Increased dwell time and occurrence of dsDNA translocation events through solid state nanopores by LiCl concentration gradients.

Solid-state nanopore based biosensors are cost effective, high-throughput engines for single molecule detection of biomolecules with the added benefit of size modification. Progress in the translation of the science into a viable diagnostic tool is impeded by inadequate sensitivity of data acquisition systems in detection of fast DNA translocations through the pore. To combat this, slowing the transport of DNA through the nanopore by use of various media or by altering experimental parameters is common. Applying a concentration gradient of KCl in the experimental ionic solution has been shown to effectively prolong dwell times as well as increase the capture rate of DNA by the nanopore. Our previous work has corroborated the ability of LiCl ionic solution to slow down the transport of dsDNA through the nanopore by up to 10-fold through cation-DNA interactions. However, this drastically reduced the event occurrence frequency, thus hindering the efficacy of this system as a reliable biosensor downstream. Here, we present the use of a concentration gradient of lithium chloride ionic solution to increase the event frequency of single molecule dsDNA translocation through a solid state nanopore. By using 0.5 M/3 M LiCl on the cis/trans chambers respectively, average dwell times experienced up to a 3-fold increase when compared to experiments run in symmetric 1 M LiCl. Additionally, experiments using the 0.5 M/3 M displayed a greater than 10-fold increase in event frequency, confirming the capture propensity of the asymmetric conditions.