Donnan Potentials in Aqueous Phase-Separated Polymer Mixtures

Vis, Mark; Peters, Vincent F. D.; Tromp, R. Hans; Erné, Ben H.

doi:10.1021/la501068e

Cited by 41 publications

(54 citation statements)

References 38 publications

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“…With increasing TLL and polymer molecular weight, cell adsorption at the interface increased. Although this theory of a “charge‐dependent partitioning” is supported by the findings of different groups, doubts have been expressed about the existence of an electrochemical potential in ATPS . Despite the debate about the existence of Donnan potentials and their significance in cell partitioning, the data presented here show a clear influence of sodium phosphate on cell partitioning and the resolution of different cell types.…”

Section: Discussionsupporting

confidence: 57%

“…It has been shown that salts with polyvalent anions, e.g., phosphate have a higher affinity for the dextran‐rich bottom phase that the PEG‐rich top phase, while salts of halides, for example, NaCl, partition almost equally between the phases . It was further proposed that unequal partitioning of a salt results in the generation of an interfacial electrostatic potential difference (Donnan potential), and molecules and particles partition in such ATPS according to their surface charge . In PEG‐dextran, ATPS containing phosphate with moderate interfacial tensions cells can, therefore, be separated based on surface charge differences (“charge‐dependent partitioning”).…”

Section: Discussionmentioning

confidence: 99%

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Cell Separation in Aqueous Two‐Phase Systems − Influence of Polymer Molecular Weight and Tie‐Line Length on the Resolution of Five Model Cell Lines

Zimmermann

Gretzinger

Zimmermann

et al. 2017

Biotechnology Journal

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The availability of clinical-scale downstream processing strategies for cell-based products presents a critical juncture between basic research and clinical development. Aqueous two-phase systems (ATPS) facilitate the label-free, scalable, and cost-effective separation of cells, and are a versatile tool for downstream processing of cell-based therapeutics. Here, we report the application of a previously developed robotic screening platform, here extended to enable a multiplexed high-throughput cell partitioning analysis in ATPS. We investigated the influence of polymer molecular weight and tie-line length on the resolution of five model cell lines in "charge-sensitive" polyethylene-glycol (PEG)-dextran ATPS. We show, how these factors influence cell partitioning, and that the combination of low molecular weight PEGs and high molecular weight dextrans enable the highest resolution of the five cell lines. Furthermore, we demonstrate that the separability of each cell line from the mixture is highly dependent on the polymer molecular weight composition and tie-line length. Using a countercurrent distribution model we demonstrate that our screenings yielded conditions that theoretically enable the isolation of four of the five cell lines with high purity (>99.9%) and yield.

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Section: Discussionsupporting

confidence: 57%

Section: Discussionmentioning

confidence: 99%

Cell Separation in Aqueous Two‐Phase Systems − Influence of Polymer Molecular Weight and Tie‐Line Length on the Resolution of Five Model Cell Lines

Zimmermann

Gretzinger

Zimmermann

et al. 2017

Biotechnology Journal

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“…Detailed accounts on sample preparation, Donnan potential measurements, and the analysis of the composition of the coexisting phases, are given in ref 9.…”

Section: ■ Experimental Sectionmentioning

confidence: 99%

“…From the optical rotation at various wavelengths and the dilution factors, the mass fractions of dextran and gelatin in the original sample were obtained for each phase. 9 The measurement principle is based on the fact that both polymers are optically active and that their optical rotary dispersionthe dependence of optical rotation on wavelengthis different. As mentioned in the Theory section, for a given sample, the tie-line length is defined as…”

Section: ■ Experimental Sectionmentioning

confidence: 99%

Effects of Electric Charge on the Interfacial Tension between Coexisting Aqueous Mixtures of Polyelectrolyte and Neutral Polymer

et al. 2015

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Upon demixing, an aqueous solution of a polyelectrolyte and an incompatible neutral polymer yields two phases separated by an interface with an ultralow tension. Here, both in theory and experiment, we study this interfacial tension in detail: how it scales with the concentrations of the polymers in the two phases and how it is affected by the interfacial difference in the electrical potential. Experiments are performed on an aqueous model system of uncharged dextran and charged nongelling gelatin. The experimental tension scales to the power ∼3 with the tie-line length in the phase diagram of demixing, in agreement with mean-field theory where space is filled with a binary mixture of polymer blobs. The interfacial electrical potential difference is experimentally found to decrease the interfacial tension in a way that is consistent with Poisson−Boltzmann theory inspired from Frenkel and Verwey−Overbeek. ■ INTRODUCTIONWhen aqueous solutions of polymers are mixed, phase separation is a commonly observed phenomenon. 1−4 It yields phases that differ in the concentrations of the polymers. The interface between the phases is not abrupt, but there are gradients in the relative composition and the total concentration of the polymers. A particularity of phase separating solutionsas opposed to phase separated blendsresults from the osmotic compressibility of the solutions: compared to the bulk phases, the interfacial region is diluted by uptake of solvent. 5 In the case of charged polymers, there is also an interfacial gradient in the electric charge density, corresponding to an interfacial electric potential step. This is the so-called Donnan potential, 6,7 and its effect on the interfacial tension is the subject of this paper.The main conditions for phase separation are a sufficient concentration and a sufficient degree of polymerization. These two factors often make the unfavorable mixing enthalpy dominate over the small mixing entropy of two types of polymer. Phase separation is also affected by the presence of charge on the polymers. 8 For instance, when one of the polymers is charged and the other is uncharged, phase separation becomes entropically more unfavorable due the accumulation of counterions in one of the phasesnecessary for charge neutrality. In order to increase entropy, the positive and negative salt ions spread across the interface to different extents; the buildup of charge separation halts the spreading.The accompanying electric potential difference is the Donnan potential. It has the same origin as the well-known membrane potential found in living cells and dialysis membranes. However, in our case, the charged interface is formed spontaneously and in equilibrium with the bulk phases; moreover, the interfacial electric potential step is relatively small, typically less than 10 mV, 9 as compared to 40−60 mV for the membranes of living cells.The electric interfacial potential step contributes negatively to the interfacial tension due to the spontaneous formation of interfacial electrical double layer...

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“…Proteins have been demonstrated that, along with polysaccharides, can be used in phase-separated mixtures to texturize water (Vis et al, 2014). Such cases have been studied in detail in model aqueous systems containing two biopolymers since the late seventies.…”

mentioning

confidence: 99%