Tajparast Mohammad, Glavinovic Mladen
Department of Civil Engineering and Applied Mechanics, McGill University, Montreal, PQ Canada.
Department of Physiology, McGill University, 3655 Sir William Osler Promenade, Montreal, P.Q. H3G 1Y6 Canada.
Bionanoscience. 2022;12(3):927-945. doi: 10.1007/s12668-022-00990-2. Epub 2022 May 19.
Interest is growing in nanopores as real-time, low-cost, label-free virus size sensors. To optimize their performance, we evaluate how external electric field and ion concentrations and pore wall charges influence currents and object (disk) radius-current relationship using simulations. The physics was described using the Poisson-Nernst-Planck and Navier-Stokes equations. In a charged cylindrical nanopore with a charged disk, elevated external electric field produces higher (and polarity independent) ion concentrations and greater ion current (largely migratory). Elevated external ion concentrations also lead to higher concentrations (mainly away from the pore wall), greater axial electric field especially in the disk-pore wall space, and finally larger current. At low concentrations, current is disk radius independent. The current rises as concentrations increase. Interestingly, the rise is greater for larger disks (except when the pore is blocked mechanically). Smaller cross-sectional area for current flow or volume exclusion of electrolyte by object thus cannot be universally accepted as explanations of current blockage. Ion current rises when pore wall charge density increases, but its direction is independent of charge sign. Current-disk radius relationship is also independent of pore wall charge sign. If the pore wall and disk charges have the same sign, larger current with bigger disk is due to higher counter-ion accumulation in the object-pore wall space. However, if their signs are opposite, it is largely due to elevated axial electric field in the object-pore wall space. Finally in uncharged nanopores, current diminishes when disk radius increases making them better sensors of virus size.
作为实时、低成本、无标记的病毒大小传感器，纳米孔正日益受到关注。为了优化其性能，我们通过模拟评估外部电场、离子浓度和孔壁电荷如何影响电流以及物体（圆盘）半径与电流的关系。使用泊松 - 能斯特 - 普朗克方程和纳维 - 斯托克斯方程来描述相关物理过程。在带有带电圆盘的带电圆柱形纳米孔中，外部电场升高会产生更高的（且与极性无关的）离子浓度和更大的离子电流（主要是迁移电流）。外部离子浓度升高还会导致更高的浓度（主要远离孔壁）、更大的轴向电场，尤其是在圆盘 - 孔壁空间中，最终产生更大的电流。在低浓度时，电流与圆盘半径无关。随着浓度增加，电流上升。有趣的是，对于较大的圆盘，电流上升幅度更大（除非孔被机械堵塞）。因此，电流流动的较小横截面积或物体对电解质的体积排斥不能被普遍接受为电流阻塞的解释。当孔壁电荷密度增加时，离子电流上升，但其方向与电荷符号无关。电流 - 圆盘半径关系也与孔壁电荷符号无关。如果孔壁和圆盘电荷具有相同的符号，较大圆盘产生更大电流是由于物体 - 孔壁空间中更高的反离子积累。然而，如果它们的符号相反，则主要是由于物体 - 孔壁空间中轴向电场升高。最后，在不带电的纳米孔中，当圆盘半径增加时电流会减小，这使得它们成为更好的病毒大小传感器。
