Influence of concentration polarization on DNA translocation through a nanopore

Abstract

Concentration polarization can be induced by the unique ion-perm selectivity of small nanopores, leading to a salt concentration gradient across nanopores. This concentration gradient can create diffusioosmosis and induce an electric field, affecting ionic currents on DNA that translocates through a nanopore. Here this influence is theoretically investigated by solving the continuum Poisson-Nernst-Planck model for different salt concentrations, DNA surface charge densities, and pores’ properties. By implementing the perturbation method, we can explicitly compute the contribution of concentration polarization to the ionic current. The induced electric field by concentration polarization is opposite to the imposed electric field and decreases the migration current and the induced diffusioosmosis can decrease the convection current as well. Our studies suggest that the importance of the concentration polarization can be determined by the parameter λ/G where λ is the double layer thickness and G is the gap size. When λ/G is larger than a critical value, the influence of concentration polarization becomes more prominent. This conclusion is supported by the studies on the dependence of the ionic current on salt concentration and pore’s properties, showing that the difference between two models with and without accounting for concentration polarization is larger for low salts and small pores, which correspond to larger λ/G.

Salt Gradient Modulation of MicroRNA Translocation through a Biological Nanopore

“…The authors postulated that salt gradients enhance the electric funneling field near the pore entrance, and also increase the electro-osmotic counterflow inside the pore, 22 which was later supported by a number of comprehensive theoretical studies on KCl salt gradients over solid-state nanopores. [23][24][25][26][27][28][29][30][31][32] Kowalczyk et al also investigated alternative electrolyte species, concluding that DNA dwell times in a silicon nitride pore increase when symmetrical KCl is replaced with NaCl or LiCl because of stronger DNA binding of these smaller cations. 33…”

The origin of the voltage dependence of conductance blockades from DNA translocation through solid-state nanopores

“…The ion concentration gradient will reduce the strength of the electric field, and result in the suppression of ionic current. 24,39 Both dsDNA and SiN surfaces are negatively charged in pH-neutral solution; and the surface charge density of dsDNA is stronger than that of SiN. 40 Therefore, the dsDNA leads to a larger ion concentration difference than the open pore state and reduces electric field intensities (Fig.…”

“…21,22 Besides, the surface charge induces ionic concentration polarization (ICP) which can change the concentration distribution and modulate the ionic current. 23,24 In addition, the electroosmotic flow (EOF) may influence the surface conductance and ICP as well. 25 In most of the literature studies, all these surface charge related factors show a prominent effect on the resistive pulses only for relatively small pores and low electrolyte concentrations.…”

Short channel effects on electrokinetic energy conversion in solid-state nanopores

“…On the other hand, a mechanical pressure-driven flow through the nanopore/nanochannel will carry a net charge within the electrical double layer, inducing an electrical current/potential and thus transforming the energy from mechanical to electric 4 . The maneuverable nanoscale ionic and fluidic transport, and the associated energy conversion can find promising applications such as ion diodes 5 10 11 , ionic transistors 2 7 12 13 , power-generators 3 4 14 , water desalination devices 15 16 17 18 and genome sequencing devices 19 20 21 . For application purposes, higher conversion efficiency between electrical and mechanical energy is being pursued.…”