Protein Diffusion Across the Interface in Aqueous Two-Phase Systems

Abstract

We present a detailed study of the diffusive transport of proteins across a fluid phase boundary within aqueous two-phase systems. The aim of the work is to investigate whether local effects at the phase boundary cause a retardation of the diffusive transport between the phases. Possible modifications of interfacial mass transfer could be due to protein adsorption at the phase boundary or local electric fields from electric double layers. Experiments with a microfluidic system have been performed in which protein diffusion (bovine serum albumin and ovalbumin) within a bilaminated configuration of two phases containing polyethylene glycol and dextran is analyzed. A one-dimensional model incorporating phase-specific diffusion constants and the difference in chemical potential between the phases has been formulated. A comparison of experimental and simulation data shows a good overall agreement and suggests that a potential local influence of the phase boundary on protein transport is insignificant for the systems under investigation.

Microfluidic extraction using two phase laminar flow for chemical and biological applications

“…In addition, for the development of the more efficient two-phase extraction based microfluidic channel, new approaches have been recently demonstrated by applying an additional electric field and introducing the affinitive metal ions to target sample [49]. In this section, a number of applications based on two-phase extraction system are introduced.…”

“…Aqueous Two-phase Extraction for Bio-application in Microfluidic System As described above, ATPS has good biocompatibility, easy adjustment, and special selectivity. Thus, ATPS has received much attention in recovery and purification of a variety of biological products including protein, genetic materials, and cells [28,29,47,49,69]. Microfluidic devices can potentially enhance ATPS because the surface areato-volume ratio of the streams is very large, decreasing the distance a cell must travel before coming into contact with a phase interface and potentially making separations faster.…”

“…For the separation of biological sample, most experiment results have been mainly focused on the affinity between the surface of biological sample and solution of ATPS owing to differences in size, charge, and hydrophobicity [13,27,49,[71][72][73]. Nevertheless some researchers suggested the mechanisms of phase forming and partitioning of biomolecules, but the exact mechanisms are still not well understood.…”

“…Similar to the cell separation approaches, protein partitioning in such an ATPS takes place due to different affinities of a protein species to the polymers. The affinities and by that the migration across the phase boundary depend on the physico-chemical properties of the protein such as isoelectric point, surface hydrophobicity, molecular mass as well as on medium properties like polymer molecular mass, pH, and salt concentrations [49,69,74]. By controlling these factors, the selective partitioning and recovery of a target protein can be achieved.…”

Mixing process of immiscible fluids in microchannels

“…In the vicinity of a separation surface, the local kinematics within each phase influence directly the rate of diffusion and mass transfer between the fluids in contact, see also Münchow et al (2008). In microchannels with an aspect ratio close to one, the liquid-liquid displacement produces unsteady 3D-vortical structures in the neighbourhood of an interface, phenomena which induces a local mixing similar to pulsatile flows (Hitt and McGarr, 2004).…”