Gel electrophoresis of a charge‐regulated, bi‐functional particle

Abstract

Adopting a Brinkman fluid model, we analyzed the electrophoresis of a charged-regulated, bi-functional particle containing both acidic and basic functional groups in a gel solution. Both the long-range hydrodynamic effect arising from the liquid drag and the short-range steric effect from particle-polymer interaction are considered. The type of particle considered is capable of simulating both biocolloids such as microorganisms and cells, and particles with adsorbed polyelectrolyte or membrane layer. Our model describes successfully the experimental data in the literature. The presence of gel has the effect of reducing the particle mobility and alleviating double-layer polarization so that the particle behavior is less complicated than that in the case where gel is absent. On the other hand, both the quantitative and qualitative behaviors of a particle depend highly on solution pH and background salt concentration, yielding interesting and significant results. These results provide valuable information for both experimental data interpretation and electrophoresis devices design.

Electrophoresis of pH-regulated nanoparticles: impact of the Stern layer

“…In this study, we investigate, for the first time, the surface charge properties and electrophoresis of pH-regulated silica NPs with simultaneous consideration of the Stern layer effect and surface protonation/deprotonation reactions on the particle wall. The model extends the previous analyses, where either the Stern layer effect or the surface chemistry reactions on the particle surface were neglected, [19][20][21][31][32][33][34][35][36][37][38][39][40][41][42][43] to the more general case much closer to the reality. In addition to the model validation by the existing experimental data of the electrophoretic mobility of silica NPs, the key parameters including the background salt concentration, pH, particle size, and surface capacitance of the Stern layer are examined comprehensively to demonstrate their influence on the zeta potential and electrophoretic behavior of the silica NP.…”

“…where R and T are the universal gas constant and absolute temperature, respectively; c s is the surface potential of the NP. Eqn ( 1) and (2) imply that s s is dominated by c s (not the zeta potential of the NP, c d ), but in previous literature for chargeregulated particles, 19,20,[32][33][34][35][36][37][38][39][40][41][42][43][44][45][46][47][48] c s is all assumed to be the same as c d for simplicity. Note that only c d (not c s ) can be determined directly from experimental measurements.…”

“…However, to the best of our knowledge, there are still no references to explore the influence of the Stern layer on the electrophoresis of charge-regulated colloidal particles. In previous studies on the surface charge properties [32][33][34] and the electrophoretic behavior 19,20,[35][36][37][38][39][40][41][42][43] of charge-regulated particles, the Stern layer effect was generally neglected, implying that the surface potential at the particle wall/liquid interface and the zeta potential at the Stern layer/diffusive layer interface of charged particles are identical. The assumption of neglecting the Stern layer effect, though makes the analysis much simplifier, could result in not only a wrong estimation of the zeta potential and electrophoretic mobility of particles, but an incorrect description of their behaviors.…”

Electrokinetic actuation of an uncharged polarizable dielectric droplet in charged hydrogel medium

“…The screening length can vary with the gel weight concentration. Hsu et al [37] has provided a relation by which a correspondence between the hydrodynamic screening length used in the mathematical model can be related to the agarose gel properties. Experimental results show that the typical hydrodynamic screening length for a agarose gel can be [38].…”

Diffusiophoretic mobility of charge‐regulating porous particles

“…The previous analytical studies of the diffusiophoresis of charged particles have usually assumed that either their fixed charge density or their zeta potential is constant. However, the fixed charge density and surface potential of many particles in practice, such as biological cells, are often developed by the association/dissociation reactions and density distribution of their ionogenic functional groups [25][26][27][28][29][30][31][32][33][34][35]. When such a charge-regulating particle is subject to a prescribed electrolyte concentration gradient (that can induce a macroscopic electric field), its fixed charge density or surface potential is a function of the local concentration of the charge-or potential-determining ions and it undergoes diffusiophoresis accordingly.…”