Effect of surface modification on aggregation of phospholipid vesicles.

Wu, Po-Shun; Tin, George W.; Baldeschwieler, John D.; Shen, T. Y.; Ponpipom, Mitree M.

doi:10.1073/pnas.78.10.6211

Cited by 17 publications

(8 citation statements)

References 20 publications

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“…Interactions between phospholipid vesicles continue to be studied as models for cellular and subcellular adhesion, aggregation, and fusion processes (Wu et al, 1981;Wong and Thompson, 1982;Cohen et al, 1982;Duzgunes et al, 1981;Wilschut et al, 1981). Additional motivation for such studies is to evaluate lipid vesicles as potential encapsulation systems for drug delivery and release in humans.…”

Section: Introductionmentioning

confidence: 99%

Free energy potential for aggregation of mixed phosphatidylcholine/phosphatidylserine lipid vesicles in glucose polymer (dextran) solutions

Evans¹,

Metcalfe²

1984

Biophysical Journal

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The energetics of lipid vesicle-vesicle aggregation in dextran (36,000 mol wt) solutions have been studied with the use of micromechanical experiments. The affinities (free energy reduction per unit area of contact) for vesicle-vesicle aggregation were determined from measurements of the tension induced in an initially flaccid vesicle membrane as it adhered to another vesicle. The experiments involved controlled aggregation of single vesicles by the following procedure: two giant (approximately 20 micron diam) vesicles were selected from a chamber on the microscope stage that contained the vesicle suspension and transferred to a second chamber that contained a dextran (36,000 mol wt) salt solution (120 mM); the vesicles were then maneuvered into position for contact. One vesicle was aspirated with sufficient suction pressure to create a rigid sphere outside the pipette; the other vesicle was allowed to spread over the rigid vesicle surface. The aggregation potential (affinity) was derived from the membrane tension vs. contact area. Vesicles were formed from mixture of egg lecithin (PC) and phosphatidylserine (PS). For vesicles with a PC/PS ratio of 10:1, the affinity showed a linear increase with concentration of dextran; the values were on the order of 10(-1) ergs/cm2 at 10% by weight in grams. Similarly, pure PC vesicle aggregation was characterized by an affinity value of 1.5 X 10(-1) ergs/cm2 in 10% dextran by weight in grams. In 10% by weight in grams solutions of dextran, the free energy potential for vesicle aggregation decreased as the surface charge (PS) was increased; the affinity extrapolated to zero at a PC/PS ratio of 2:1. When adherent vesicle pairs were transferred into a dextran-free buffer, the vesicles did not spontaneously separate. They maintained adhesive contact until forceably separated, after which they would not read here. Thus, it appears that dextran forms a "cross-bridge" between the vesicle surfaces.

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Section: Introductionmentioning

confidence: 99%

Free energy potential for aggregation of mixed phosphatidylcholine/phosphatidylserine lipid vesicles in glucose polymer (dextran) solutions

Evans¹,

Metcalfe²

1984

Biophysical Journal

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“…We therefore prepared small unilamellar POPC vesicles (SUVs) that contained undecylimidazole. Such small, neutral sonicated vesicles can be unstable and tend to aggregate or fuse with available membranes12 bringing their cargo in close proximity to the surface of GUVs. Since undecylimidazole is a single‐chain amphiphile, it should be able to exchange between vesicle membranes and flip‐flop across the phospholipid bilayer to access the interior of the giant phospholipid vesicles 13.…”

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confidence: 99%

Electrostatic Localization of RNA to Protocell Membranes by Cationic Hydrophobic Peptides

et al. 2015

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Cooperative interactions between RNA and vesicle membranes on the prebiotic earth may have led to the emergence of primitive cells. The membrane surface offers a potential platform for the catalysis of reactions involving RNA, but this scenario relies upon the existence of a simple mechanism by which RNA could become associated with protocell membranes. Here, we show that electrostatic interactions provided by short, basic, amphipathic peptides can be harnessed to drive RNA binding to both zwitterionic phospholipid and anionic fatty acid membranes. We show that the association of cationic molecules with phospholipid vesicles can enhance the local positive charge on a membrane and attract RNA polynucleotides. This phenomenon can be reproduced with amphipathic peptides as short as three amino acids. Finally, we show that peptides can cross bilayer membranes to localize encapsulated RNA. This mechanism of polynucleotide confinement could have been important for primitive cellular evolution.

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“…The spontaneous aggregation and fusion of neutral phospholipid vesicles has been studied in some detail and is believed to be caused by structural instabilities brought on by the packing requirements for bilayer lipids to form small unilamellar vesicles (15,16). Because the initial sizes ofthe two types ofvesicles are similar (Figs.…”

Section: Resultsmentioning

confidence: 99%

“…as described (14). Vesicle aggregation and fusion in buffered solution was monitored by light scattering (15). 2H NMR spectra were obtained with a Bruker WM 500 spectrometer equipped with a BVT 1000 variable-temperature controller.…”

mentioning

confidence: 99%

Stability of carbohydrate-modified vesicles in vivo: comparative effects of ceramide and cholesterol glycoconjugates.

Wu¹,

Wu²,

Tin³

et al. 1982

Proc. Natl. Acad. Sci. U.S.A.

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The stability and tissue distribution of lipid vesicles modified at the surface by the incorporation ofeither a galactosyl ceramide (GalCer)'or a galactosyl'cholesterol (GalChol) glycoconjugate have been studied in. mice by measuring the release of vesicle-entrapped "'1In. Although the tissue distributions of both vesicle types were similar, the GalCer-containing vesicles were markedly less stable than those. prepared with GalChol, whether administered orally or by intraperitoneal injection. Physical characterization of the vesicles in vitro suggests that the increased disruption rate for GalCer vesicles in vivo is related to. structural instabilities induced by the cerebroside, which can then result in either an increased rate of vesicle uptake by tissues or a greater susceptibility to lysis. These studies demonstrate the importance ofthe nonpolar anchoring groups in determining the fate of surface-modified vesicles in vivo.The targeting ofencapsulated agents, such as drugs or enzymes, to specific tissues is one of the goals in the development of liposomes as exogenous delivery systems. To achieve this result, a number of strategies have been attempted, including the addition ofcharged lipids to neutral vesicles (1), the covalent binding of antibodies to vesicle surfaces (2), and the use oflocalized hyperthermia to induce phase transitions in synthetic liposomes (3). The finding that mammalian hepatocyte surfaces contain a galactose-specific glycoprotein binding site (4) has led to studies on the usefulness ofcarbohydrate-modified vesicles in targeting encapsulated materials (5-7). Initial work has shown great promise (7), leading to further investigation ofvariables that can affect the system. Due to the amphiphilic nature of vesicle bilayers, it is convenient to incorporate polar carbohydrate molecules by attaching them to nonpolar lipid groups. In view' of the importance of lipid shape to vesicle structure (8), it is likely that the choice of lipid conjugate or anchoring group will, in addition to the type of carbohydrate used, affect the fate of modified vesicles in vivo. In the present communication; we report studies of carbohydrate-modified vesicles containing glycolipids differing in the structure oftheir nonpolar group. The results, comparing the effects of N-stearoyl-DL-dihydrogalactocerebroside (galactosyl ceramide, GalCer, II) with those of 6-(5-cholesten-3f-yloxy)hexyl-l-thio-(3-D-galactopyranoside (galactosyl cholesterol, GalChol, I) demonstrate the importance of the carbohydrate anchoring group in maintaining stable vesicles in vivo.

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Effect of surface modification on aggregation of phospholipid vesicles.

Cited by 17 publications

References 20 publications

Free energy potential for aggregation of mixed phosphatidylcholine/phosphatidylserine lipid vesicles in glucose polymer (dextran) solutions

Free energy potential for aggregation of mixed phosphatidylcholine/phosphatidylserine lipid vesicles in glucose polymer (dextran) solutions

Electrostatic Localization of RNA to Protocell Membranes by Cationic Hydrophobic Peptides

Stability of carbohydrate-modified vesicles in vivo: comparative effects of ceramide and cholesterol glycoconjugates.

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