Controlling pH-Regulated Bionanoparticles Translocation through Nanopores with Polyelectrolyte Brushes

Abstract

A novel polyelectrolyte (PE)-modified nanopore, comprising a solid-state nanopore functionalized by a nonregulated PE brush layer connecting two large reservoirs, is proposed to regulate the electrokinetic translocation of a soft nanoparticle (NP), comprising a rigid core covered by a pH-regulated, zwitterionic, soft layer, through it. The type of NP considered mimics bionanoparticles such as proteins and biomolecules. We find that a significant enrichment of H(+) occurs near the inlet of a charged solid-state nanopore, appreciably reducing the charge density of the NP as it approaches there, thereby lowering the NP translocation velocity and making it harder to thread the nanopore. This difficulty can be resolved by the proposed PE-modified nanopore, which raises effectively both the capture rate and the capture velocity of the soft NP and simultaneously reduces its translocation velocity through the nanopore so that both the sensing efficiency and the resolution are enhanced. The results gathered provide a conceptual framework for the interpretation of relevant experimental data and for the design of nanopore-based devices used in single biomolecules sensing and DNA sequencing.

Ion transport and selectivity in biomimetic nanopores with pH-tunable zwitterionic polyelectrolyte brushes

“…To mimic the pH-tunable nature of bioinspired nanopores, our model extends the previous continuum-based model (see Theoretical Model section), which has been verified and is suitable for describing the underlying physics of ion transport in PE layermodified nanopores, [30][31][32][33] to the more general case with considering the presence of H + and OH − ions and chemistry reactions of the functional groups on PE chains. To mimic the pH-tunable nature of bioinspired nanopores, our model extends the previous continuum-based model (see Theoretical Model section), which has been verified and is suitable for describing the underlying physics of ion transport in PE layermodified nanopores, [30][31][32][33] to the more general case with considering the presence of H + and OH − ions and chemistry reactions of the functional groups on PE chains.…”

“…5a, b (σ m = 0.1 chains per nm 2 ) and 5c,d (σ m = 0.5 chains per nm 2 ) reveals that the larger the grafting density of PE chains on the membrane wall, the more significant the ICP phenomenon. These results clearly indicate that the assumption of homogeneously fixed charge density of PE layer [28][29][30]32,33,[51][52][53] is inappropriate and might result in an incorrect estimation for the ion transport in such soft nanofluidics with a surface modification of PE brushes. In Fig.…”

“…The following verified continuum-based model, 13,30,32,36 taking into account the presence of multiple ionic species, 32 is Fig. 1 Schematic of the ion transport in a pH-tunable, biomimetic PE layer-modified (e.g., negatively charged) nanopore filled with electrolyte solution containing four ionic species, H + , K + , Cl − , and OH − .…”

“…13,14,[21][22][23][24][25][26][27] Compared with those, available studies on the ion transport in PE layer-modified nanopores are very limited because of the complexity of mathematical model. 29 Until recently, the analyses on the electrokinetic ion 30 and nanoparticle 31,32 transport, ICP, 33 and ICR 34 in nanopores functionalized with PE brush layers have been made by using the coupled Poisson-Nernst-Planck (PNP) and modified Stokes-Brinkman equations. They found that the molecular structure of PE chains deform significantly, which in turn affects the ionic conductance in the nanopore, when the molecular length of PE chains is too long and the applied electric filed is large.…”

Electroviscous effect on the streaming current in a pH-regulated nanochannel

“…Let C i0 (in mM), i = 1, 2, 3, and 4 be the bulk concentrations of these ions, respectively, and C KCl be the background concentration of KCl. Based on electroneutrality condition, we have C 10 = C KCl , C 20 = C KCl + 10 (−pH + 3) − 10 − (14 − pH) + 3 , C 30 = 10 (−pH + 3) , and C 40 = 10 − (14 − pH) + 3 for pH ≤ 7; C 10 = C KCl − 10 (−pH + 3) + 10 − (14 − pH) + 3 , C 20 = C KCl , C 30 = 10 (−pH + 3) , and C 40 = 10 − (14 − pH) + 3 for pH N 7 [22,23]. Note that the effect of buffer solution on the adjustment of pH is neglected in the present study.…”