The lower limit to the size of small sonicated phospholipid vesicles

Cornell, Bruce; Fletcher, Guy C.; Middlehurst, J.; Separovic, Frances

doi:10.1016/0005-2736(82)90233-4

Cited by 54 publications

(33 citation statements)

References 9 publications

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“…These simulated liposomes are smaller than the experimentally observed sizes of >100 nm at 25 °C, 46 and closer to sonicated DPPC vesicles at 20 °C (~20 nm). 47 Small fragments such as micelles were not detected in experiment up to 5–10 mol% DPPE-PEG; 46 they form in the simulation because the remaining lipids are not sufficient to form another liposome. Bicelles and micelles are observed in the simulation at 10.5 mol%, and these decrease in size at 27.4 mol%; only small micelles are present at 99.0 mol% DPPE-PEG45.…”

Section: Resultsmentioning

confidence: 94%

Coarse-Grained Model for PEGylated Lipids: Effect of PEGylation on the Size and Shape of Self-Assembled Structures

2011

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Self-assembly of polyethylene glycol (PEG)-grafted lipids at different sizes and concentrations was simulated using the MARTINI coarse-grained (CG) force field. The interactions between CG PEG and CG dipalmitoylglycerophosphocholine (DPPC)-lipids were parametrized by matching densities of 19-mers of PEG and polyethylene oxide (PEO) grafted to the bilayer from all-atom simulations. Mixtures of lipids and PEG(Mw = 550, 1250, 2000)-grafted lipids in water self-assembled to liposomes, bicelles, and micelles at different ratios of lipids and PEGylated lipids. Average aggregate sizes decrease with increasing PEGylated-lipid concentration, in qualitative agreement with experiment. PEGylated lipids concentrate at the rims of bicelles, rather than at the planar surfaces; this also agrees with experiment, though the degree of segregation is less than that assumed in previous modeling of the experimental data. Charged lipids without PEG evenly distribute at the rim and planar surface of the bicelle. The average end-to-end distances of the PEG on the PEGylated lipids are comparable in liposomes, bicelles (edge or planar surface), and micelles, and only slightly larger than for an isolated PEG in solution. The ability of PEGylated lipids to induce the membrane curvature by the bulky head group with larger PEG, and thereby modulate the phase behavior and size of lipid assemblies, arises from their relative concentration.

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Section: Resultsmentioning

confidence: 94%

Coarse-Grained Model for PEGylated Lipids: Effect of PEGylation on the Size and Shape of Self-Assembled Structures

2011

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“…Therefore it appears that even very small particles can serve as nucleation sites for amphiphile organization and vesicle formation. Since these spheres are probably smaller than the smallest possible vesicles (Cormell et al, 1982), nucleation most likely involves the formation of small patches of membrane that can continue to grow at their edges independently of the silica spheres.…”

Section: Highly Curved Silica Surfacesmentioning

confidence: 99%

Mineral Surface Directed Membrane Assembly

Hanczyc

Mansy

Szostak

2006

Orig Life Evol Biosph

118

109

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The transition from non-living to living matter may have resulted from the self-organizing properties of organic molecules and their interactions with a chemically rich inorganic environment. We have shown that a solution containing RNA, fatty acids and clay produces structures that contain a potentially catalytic surface (clay) and a potential informational biopolymer (RNA) encapsulated within a membrane. This highlights the ability of mineral surfaces to bring together and organize key components of primordial life. We have extended our analysis of mineral-mediated vesicle catalysis to include other natural minerals and synthetic surfaces of varying shape, size, and charge density. Our results show that while RNA polymerization on minerals may be restricted to the surface environment provided by montmorillonite, vesicle formation is enhanced in the presence of disparate types of surfaces. A model is presented in which new sheets of amphiphiles form just proximal to a surface. Similar interactions between amphiphiles and minerals on early Earth may have resulted in the encapsulation of a diverse array of mineral particulates with catalytic properties.

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“…As a result, the nanoprecipitates of cisplatin are not covered by the DOPC/ DOPS bilayer during the formation of nanocapsules, unless their diameter is at least 30-40 nm, which is only slightly larger than the diameter of sonicated vesicles, the most strongly curved bilayers formed by phospholipids. 34 The virtual absence of nanocapsules with larger diameters suggests that the diameter size of the nanoprecipitate is ratelimiting for nanocapsule formation. We speculate that the elongated rather than spherical geometry of the nanocapsules originates from a preferential direction in cisplatin crystal growth under the conditions of preparation.…”

Section: Molecular Organization Of Cisplatin Nanocapsulesmentioning

confidence: 99%

Molecular Architecture of Nanocapsules, Bilayer-Enclosed Solid Particles of Cisplatin

2004

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Cisplatin nanocapsules represent a lipid formulation of the anticancer drug cis-diamminedichloroplatinum(II) (cisplatin) characterized by an unprecedented cisplatin-to-lipid ratio and exhibiting strongly improved cytotoxicity against tumor cells in vitro as compared to the free drug (Burger, K. N. J., et al. Nat. Med. 2002, 8, 81-84). Cisplatin nanocapsules are prepared by the repeated freezing and thawing of an equimolar dispersion of phosphatidylserine (PS) and phosphatidylcholine (PC) in a concentrated aqueous solution of cisplatin. Here, the molecular architecture of these novel nanostructures was elucidated by solid-state NMR techniques. 15 N NMR and 2 H NMR spectra of nanocapsules containing 15 N-and 2 H-labeled cisplatin, respectively, demonstrated that the core of the nanocapsules consists of solid cisplatin devoid of free water. Magic-angle spinning 15 N NMR showed that ∼90% of the cisplatin in the core is present as the dichloro species. The remaining 10% was accounted for by a newly discovered dinuclear Pt compound that was identified as the positively charged chloride-bridged dimer of cisplatin. NMR techniques sensitive to lipid organization, 31 P NMR and 2 H NMR, revealed that the cisplatin core is coated by phospholipids in a bilayer configuration and that the interaction between solid core and bilayer coat exerts a strong ordering effect on the phospholipid molecules. Compared to phospholipids in liposomal membranes, the motion of the phospholipid headgroups is restricted and the ordering of the acyl chains is increased, particularly in PS. The implications of these findings for the structural organization, the mechanism of formation, and the mode of action of cisplatin nanocapsules are discussed.

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The lower limit to the size of small sonicated phospholipid vesicles

Cited by 54 publications

References 9 publications

Coarse-Grained Model for PEGylated Lipids: Effect of PEGylation on the Size and Shape of Self-Assembled Structures

Coarse-Grained Model for PEGylated Lipids: Effect of PEGylation on the Size and Shape of Self-Assembled Structures

Mineral Surface Directed Membrane Assembly

Molecular Architecture of Nanocapsules, Bilayer-Enclosed Solid Particles of Cisplatin

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