Electrophoresis of Liquid-Layer Coated Particles: Impact of Ion Partitioning and Ion Steric Effects

Abstract

The biomimetic core–shell nanoparticles coated with membranes of various biological cells have attracted significant research interest, because of their extensive applications in targeted drug delivery systems. The cell membrane consists of a lipid bilayer, which can be regarded as a two-dimensional oriented viscous liquid with low dielectric permittivity, compared to a bulk aqueous medium. Such a liquid layer comprised of cell membrane may bear additional mobile charges, because of the presence of free lipid molecules or charged surfactant molecules, which further results in nonzero charge along the surface of the peripheral layer. In this article, we present an analytical theory for electrophoresis of such cell membrane coated functionalized nanoparticles in the extent of electrolyte solution, considering the combined effects of finite ion size and of ion partitioning. Going beyond the Debye–Huckel approximations, we propose an analytical theory for Donnan potential and electrophoretic mobility. The derived expressions are applicable for moderate to highly charged undertaken core–shell particles when the thickness of the peripheral liquid layer greatly exceeds the electric double layer thickness. The impact of pertinent parameters on the electrophoretic response of such a particle is further discussed.

Streaming Potential and Associated Electrokinetic Effects through a Channel Filled with Electrolyte Solution Surrounded by a Layer of Immiscible and Dielectric Liquid

“…Besides, the charged surfactant molecules that exist in the peripheral layer may be in the form of dimer micelles or small micelles with low aggregation numbers, all of which can be treated as free mobile ions. 54 The solubility of such molecules in the water phase is negligibly small. 52,63 Thus, we may assume these ions that lead to net volumetric charge across the peripheral layer are present in the dielectric liquid layer, and thus its concentration within the electrolytic medium is assumed as zero.…”

“…51 In addition, an equivalent EDL may further form toward the dielectric liquid layer which contains both the electrolyte ions as well as additional mobile ions. 52,54,63,64 Note that the thicknesses of both of these EDLs, along the water side as well as the immiscible layer of dielectric liquid, are denoted by κ −1 and κ d −1…”

“…In addition, such layers may bear free lipid molecules or charged surfactants, all of which can be treated as free mobile ions. 54 Besides, the electrolyte ion can penetrate across this layer depending on the difference in the Born energy of the respective phases. 55 In this article, we extensively studied the generation of streaming potential and associated electrokinetic effects across such microfluidic devices.…”

Electrohydrodynamics of diffuse porous colloids

“…Existing studies 68,69 indicate that the Carnahan-Stirling model 66 is suitable and can correctly measure the ion steric effect. Subsequently, several researchers studied the electrophoresis of rigid colloids 70,71 and core-shell structured composite nanoparticles [72][73][74] considering the ion steric interaction based on the Carnahan Stirling model. 66 Note that the soft particles [72][73][74] are closely related to porous particles, in which a rigid core is covered with the polymeric shell layer.…”

“…Subsequently, several researchers studied the electrophoresis of rigid colloids 70,71 and core-shell structured composite nanoparticles [72][73][74] considering the ion steric interaction based on the Carnahan Stirling model. 66 Note that the soft particles [72][73][74] are closely related to porous particles, in which a rigid core is covered with the polymeric shell layer. However, the electrohydrodynamics of rigid and soft particles is different from that of full porous particles.…”