PubMed Health⌕ Search
Home/Archive/PubMed

PubMed · 12418876

Aqueous phase separation in giant vesicles.

Marcus R Helfrich·Lauren K Mangeney-Slavin·M Scott Long·Karrera Y Djoko·Christine D Keating
View original source ↗Export metadata ↓

Abstract

We report the synthesis and initial characterization of approximately 10 mum diameter lipid vesicles that contain two distinct aqueous phases. The aqueous two-phase system is a dextran/poly(ethylene glycol) solution that exhibits temperature-dependent phase behavior. Vesicles were prepared above the phase transition temperature of the polymer solution. Upon cooling to room temperature, the polymer solution phase separated both within the vesicles and in the bulk solution. The location of poly(ethylene glycol)-rich and dextran-rich phases was determined by fluorescence microscopy. These structures are exciting in that they enable for the first time the interior volume of liposomes to be structured.

Explore related subjects

DextransFluorescein-5-isothiocyanateLiposomesPhosphatidylcholinesPhosphatidylglycerolsPolyethylene GlycolsWaterJournal ArticleResearch Support, Non-U.S. Gov'tResearch Support, U.S. Gov't, Non-P.H.S.

Keep this discovery

Explore connections, maps & timelines

BibTeXRIS

Marcus R Helfrich, Lauren K Mangeney-Slavin, M Scott Long, Karrera Y Djoko, Christine D Keating. 2002-11-13. Aqueous phase separation in giant vesicles.. https://doi.org/10.1021/ja028157%2B

Cite the original work for its findings. Save a collection to share your selection of sources.

KEEP EXPLORING

Related citations

PubMed2026

Structural and physicochemical characterisation of branched dextrans produced by an active α-(1→2) branching sucrase from Apilactobacillus kunkeei PDER37.

Recently, branching sucrases encoded in the genomes of certain Lactic Acid Bacteria (LAB) strains have become novel enzymes to obtain branched α-glucans. In this study an active α-(1 → 2) branching sucrase from Apilactobacillus kunkeei PDER37 was expressed, characterised and distinct branched dextrans was obtained with reactions under different sucrose: dextran ratio. Structural characterisation by 1H and 13C NMR analysis demonstrated the branching of the dextran with (1 → 2)-linked α-d-glucose units with no alteration in the final structure depending on sucrose: dextran ratio (D0) but this ratio was effective for the determination of the molecular weights of the branched dextrans (D1, D2 and D3). FTIR analysis further supported the dextran structures and suggested the higher accumulation of the α-Glc units in the branched dextrans. Thermal characterisation of the branched dextrans obtained by TGA and DSC analysis suggested the increased hygroscopicity of the branching units. Both SEM and AFM analysis demonstrated more porous chain like structures in the branched dextrans. This study provides valuable information on the role of active α-(1 → 2) branching sucrase (BS37) for the production of branched dextrans with potential increased physicochemical status applicable for food and other industries.

Dextrans↗
PubMed2006

Incorporation of water-soluble drugs in PLGA microspheres.

Poly(lactide-co-glycolide) (PLGA) microspheres containing blue dextran, as a model of water-soluble drugs, were prepared from w(1)/o/w(2) emulsions by using a microhomogenizer and a solvent evaporation method. Effects of preparation conditions, such as, concentration of poly(vinyl alcohol) (PVA) in w(2) phase, viscosity of inner soluble water phase, volume ratio of oil phase to w(1) phase in primary emulsion, PLGA concentration in oil phase, and molecular weight or composition of PLGA, upon the properties of PLGA microspheres containing water-soluble drugs were examined. Concentration of poly(vinyl alcohol) (PVA), the dispersant dissolved in w(2) phase of secondary emulsion did not show any effects on the final particle size. On the other hand, volume ratio of oil phase to water one in primary emulsion affected the final particle size, which seemed to be related to the local PLGA concentration in w(1)/o emulsions. That is, the particle size increased as the volume ratio of w(1) phase against oil phase, w(1)/o (v/v), increased. The loading efficiency, however, was not affected by the volume ratio of w(1)/o (v/v), but affected by blue dextran concentration in w(1) phase. Higher loading efficiency was observed in PLGA microspheres prepared from w(1) phase containing lower concentration of blue dextran. Blue dextran solution (inner water phase) with the lower viscosity may result in the lower leakage ratio of blue dextran during the preparation procedure. Increases in concentration and molecular weight of PLGA made particle size larger.

Dextrans↗
PubMed2006

Novel self-assembling nanogels: stability and lyophilisation studies.

The stability of new supramolecular nanoassemblies (nanogels), based on the association of a hydrophobically modified dextran (MD) and a beta-cyclodextrin polymer (pbetaCD), has been studied by two complementary methods: (i) size measurements and (ii) turbidity experiments using a Turbiscan optical analyser. Nanogels of about 120-150nm were obtained whatever the concentration of the two polymer solutions. At low concentrations, the suspensions presented little mean diameter variations upon storage. However, the concentrated ones tended to destabilize and their mean diameter increased upon time. Size measurements and Turbiscan investigations have demonstrated that destabilization in the MD-pbetaCD nanogel suspension was only due to particle aggregation and/or fusion, as no sedimentation or creaming occurred. The destabilization of MD-pbetaCD suspensions led to the formation of a highly viscous phase, as a final state. Moreover, the two methods have shown that aggregation and/or fusion phenomena were more pronounced in the concentrated MD-pbetaCD suspensions than in the diluted ones. The stability of MD-pbetaCD suspensions could be improved by their storage at 4 degrees C. Finally, freeze-drying was found to be a convenient method for the long-time storage of MD-pbetaCD nanoassemblies.

Dextrans↗