Aqueous biphase formation in polyethylene oxide-inorganic salt systems

Ananthapadmanabhan, K.P.; Goddard, E. D.

doi:10.1021/la00073a005

Cited by 244 publications

(220 citation statements)

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“…The (NH 4 ) 2 SO 4 solutions thus dehydrate the polymer to varying degree. These observations agree with the literature hypothesis [16,17] describing the formation of aqueous two-phase systems based on the components' (PEG and inorganic salt) competition for hydration, resulting in polymer dehydration and the formation of two immiscible aqueous phases. Table 2 Absorption maxima for water molecules bonded to PEG [14,15].…”

Section: Ir Spectra Of Solid Blank Phasessupporting

confidence: 92%

Cd(II) extraction in PEG-based two-phase aqueous systems in the presence of iodide ions. Analysis of PEG-rich solid phases

Bulgariu

Sarghie

et al. 2007

Open Chemistry

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Cd(II) plus iodide species were extracted into PEG-rich phases in the aqueous PEG(1550)-(NH 4 ) 2 SO 4 system at pH 2.05 -7.12. IR spectra show that increasing (NH 4 ) 2 SO 4 solution acidity does not protonate PEG ether oxygen atoms, but decreases water content in the PEG-rich phases. Metallic species' extraction into the PEG predominantly alters how water molecules bind to polymer chains; the changes in their absorption bands depend on pH. Microscopy shows that "fixation" of the extracted metal in the PEG-rich phase occurs by specific interactions which depend on the species. These also determine changes in the polymer chains' conformation.

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Section: Ir Spectra Of Solid Blank Phasessupporting

confidence: 92%

Cd(II) extraction in PEG-based two-phase aqueous systems in the presence of iodide ions. Analysis of PEG-rich solid phases

Bulgariu

Sarghie

et al. 2007

Open Chemistry

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“…The precipitating effect of kosmotropic salts was found to be concentration dependent, and the order of their threshold concentration was the following: sodium citrate < sodium sulfate < magnesium sulfate < ammonium sulfate (Figure 9.). This order is in good accordance with two phase forming capacity of ions in PEG-salt-water systems observed earlier [28].…”

Section: Other Kosmotropic Salts Also Lead To Precipitation Of Pegylasupporting

confidence: 91%

Aggregation of PEGylated liposomes driven by hydrophobic forces

Bozó

Mészáros

Mihály

et al. 2016

Colloids and Surfaces B: Biointerfaces

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2 Graphical Abstract 3 Highlights Kosmotropes induce the aggregation and fusion of PEG-liposomes.  The effect depends on both the kosmotrope and PEG concentration.  Aggregation is reversible under certain conditions.  Kosmotropes lead to a dehydration-related conformational change of the PEG polymer.  The likely driving force behind aggregation is the hydrophobic effect. 4 ABSTRACTPolyethylene glycol (PEG) is widely used to sterically stabilize liposomes and improve the pharmacokinetic profile of drugs, peptides and nanoparticles. Here we report that ammonium sulfate (AS) can evoke the aggregation of PEGylated vesicles in a concentration-dependent manner. Liposomes with 5 mol% PEG were colloidally stable at AS concentrations up to 0.7 mM, above which they precipitated and formed micron-size aggregates with irregular shape. While aggregation was reversible up to 0.9 M of AS, above 1 M fusion occurred, which irreversibly distorted the size distribution. Zeta potential of liposomes markedly increased from -71±2.5 mV to 2±0.5 mV upon raising the AS concentration from 0 to 0.1 M, but no considerable increase was seen during further AS addition, showing that the aggregation is independent of surface charge. There was no aggregation in the absence of the PEG chains, and increasing PEG molar % shifted the aggregation threshold to lower AS concentrations. Changes in the FTIR spectral features of PEGylated vesicles suggest that AS dehydrates PEG chains. Other kosmotropic salts also led to aggregation, while chaotropic salts did not, which indicates a general kosmotropic phenomenon. The driving force behind aggregation is likely to be the hydrophobic effect due to salting out the polymer similarly to what happens during protein purification or Hydrophobic Interaction Chromatography. Since liposome aggregation and fusion may result in difficulties during formulation and adverse reaction upon application, the phenomena detailed in this paper may have both technological and therapeutical consequences.

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“…Several investigators have studied the influence of the type of inorganic salts on the phase separation of aqueous PEG solutions, [13][14][15][16][17][18] and have suggested that the stronger is the hydration of the ion, the lower is the concentration required to form a two-phase system.…”

Section: Resultsmentioning

confidence: 99%

“…Ananthapadmanabhan and Goddard 17,18 have reported that the relative concentration of various salts to form aqueous two-phase systems with PEG 1040 ANALYTICAL SCIENCES OCTOBER 2000, VOL. 16 depends upon the valency and hydration of the ions as well as specific interactions of the ions with the ether oxygens of PEG.…”

Section: Resultsmentioning

confidence: 99%

Effects of Phase-Forming Cations and Anions on the Partition of Ionic Solutes in Aqueous Polyethylene Glycol-Inorganic Salt Two-Phase Systems

et al. 2000

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When a certain water-soluble polymer is dissolved in water together with another kind of hydrophilic polymer or with a certain inorganic salt at specific concentrations, two aqueous phases can be formed. These aqueous two-phase systems or aqueous biphasic systems have been successfully used for the separation of biological materials, such as cells, organelles, enzymes and proteins, because they essentially have a nondenaturing environment. 1,2It has also been shown that the aqueous two-phase partition technique can be efficient for the separation of inorganic compounds 2-5 and small organic molecules. 6 Although a number of different water-soluble polymers may be utilized to form aqueous two-phase systems, polyethylene glycols (PEGs) are mainly used in combination with dextrans or inorganic salts. Because PEGs are nontoxic, nonflammable and nonvolatile the PEG-based aqueous two-phase systems cause less environmental problems compared to conventional solventextraction systems utilizing water-immiscible organic solvents.The partition of solute compounds in aqueous two-phase systems depends on numerous factors originating from the polymers and inorganic salts to be used for forming the two phases. As well as the variables concerning the polymers, the type and concentration of the salts are among the most important factors. It has been demonstrated that the ionic composition in aqueous two-phase systems exerts pronounced effects on the partition of solute compounds, particularly on that of ionic solutes. 4,5,7,8 Johansson 7 has indicated that the partition coefficients of ionic solutes in a PEG-dextran two-phase system depends both on the type of salt added to the system as well as the net charge of the solute. Rogers et al. 5 investigated the partition behavior of pertechnetate ion in PEG-alkali metal and ammonium sulfate salt systems, and revealed that the trends in the partition coefficients follow from the relative salting-out ability of the salts used.However, the effects of the salts added upon the partition of solute compounds are rather complex because the concentrations of the polymers in the coexisting phases depend on the type and concentration of the salts. Zaslavsky et al. 9,10 and Bamberger et al. 11 have shown that the salt additives alter the polymer composition of the coexisting phases in the aqueous two-phase systems formed by two different polymers, such as PEG-dextran and Ficoll-dextran. This means that the ionic composition in the aqueous two-phase systems influences the partition of solutes not only by its own effect, but also by the effect on the polymer composition of the two phases. Therefore, the inherent effect of ions on the solute partitioning in aqueous two-phase systems should be evaluated under the conditions where the effect of the polymer concentrations can be regarded as being constant.In the present study, we chose PEG-salt (Na2SO4, K2HPO4 and Na2HPO4) two-phase systems and investigated the partition bahavior of inorganic cations and anions as a function of the difference in the c...

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Aqueous biphase formation in polyethylene oxide-inorganic salt systems

Cited by 244 publications

References 4 publications

Cd(II) extraction in PEG-based two-phase aqueous systems in the presence of iodide ions. Analysis of PEG-rich solid phases

Cd(II) extraction in PEG-based two-phase aqueous systems in the presence of iodide ions. Analysis of PEG-rich solid phases

Aggregation of PEGylated liposomes driven by hydrophobic forces

Effects of Phase-Forming Cations and Anions on the Partition of Ionic Solutes in Aqueous Polyethylene Glycol-Inorganic Salt Two-Phase Systems

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