DNA Electrokinetic Translocation through a Nanopore: Local Permittivity Environment Effect

The effect of the local liquid permittivity surrounding the DNA nanoparticle, referred to as the local permittivity environment (LPE) effect, on its electrokinetic translocation through a nanopore is investigated for the first time using a continuum-based model, composed of the coupled Poisson–Nernst–Planck (PNP) equations for the ionic mass transport and the Stokes and Brinkman equations for the hydrodynamic fields in the region outside of the DNA and within the ion-penetrable layer of the DNA nanoparticle, respectively. The nanoparticle translocation velocity and the resulting current deviation are systematically investigated for both uniform and spatially varying permittivities surrounding the DNA nanoparticle under various conditions. The LPE effect in general reduces the particle translocation velocity. The LPE effect on the current deviation is insignificant when the imposed electric field is relatively high. However, when the electric field and the bulk electrolyte concentration are relatively low, both current blockade and enhancement are predicted with the LPE effect incorporated, while only current blockade is predicted with the assumption of constant liquid permittivity. It is thereby shown that regardless of the electric field imposed the predictions on ionic current with considering the LPE effect are in good qualitative agreement with the experimental observations obtained in the literature.