Solid-state nanopores are sensors capable of analysing individual unlabelled DNA molecules in solution. Although the critical information obtained from nanopores (for example, DNA sequence) comes from the signal collected during DNA translocation, the throughput of the method is determined by the rate at which molecules arrive and thread into the pores. Here, we study the process of DNA capture into nanofabricated SiN pores of molecular dimensions. For fixed analyte concentrations we find an increase in capture rate as the DNA length increases from 800 to 8,000 base pairs, a length-independent capture rate for longer molecules, and increasing capture rates when ionic gradients are established across the pore. Furthermore, we show that application of a 20-fold salt gradient allows the detection of picomolar DNA concentrations at high throughput. The salt gradients enhance the electric field, focusing more molecules into the pore, thereby advancing the possibility of analysing unamplified DNA samples using nanopores.
Bibliographical noteFunding Information:
The authors would like to thank B. McNally for help in data acquisition, and support from Harvard’s Center for Nanoscale Systems (CNS). We are grateful for stimulating and fruitful discussions with M. Frank-Kamenetskii, A. Kolomeisky, O. Krichevsky, G. Lakatos, D.R. Nelson, A. Parsegian and B. Shklovskii. A.M. acknowledges support from National Institutes of Health award HG-004128 and National Science Foundation award PHY-0646637. Y.R. and A.G. acknowledge support by the US–Israel Binational Science Foundation. Y.R. acknowledges a grant from the Israeli Science Foundation and the hospitality of the NYU Department of Physics.