Abstract
Oppositely charged giant vesicles are known to adhere, hemifuse and fuse, all of which depend upon the nature of surface contacts. To further understand such interactions, vesicles were surface-modified with polyethylene glycol (PEG), a moiety that reduces surface–surface interactions. Positively charged vesicles were composed of O-ethyldioleoylphosphocholine (EDOPC), dioleoylphosphatidylcholine (DOPC) and a carbocyanine dye (DiO), with and without DPPE-PEG (dipalmitoylphosphatidylethanolamine-N-PEG MW of the PEG portion = 2000). Negatively charged vesicles were composed of dioleoylphosphatidylglycerol (DOPG), DOPC and a rhodamine B dye (Rh-PE), with as well as without DPPE-PEG (MW 2,000). A microscope-mounted electrophoresis chamber allowed selected pairs of vesicles to be brought into contact while color images were collected at video rates (30 frames/s). Data collection focused on effects of PEG on vesicle interactions as a function of the surface charge density. Relative to PEG-free preparations, vesicles containing DPPE-PEG (1) formed larger contact zones, (2) underwent adhesion and fusion processes more slowly (by two to four times) and (3) at high charge density were less susceptible to rupture upon contact. Unexpectedly, PEG-containing vesicles exhibited engulfment of a smaller by a larger vesicle, a process topologically similar to cellular endocytosis. These observations are interpreted to mean that, although initial surface–surface interactions are weakened by the intervening layer of PEG chains, eventual and strong bilayer–bilayer contact is still possible, evidently because the lipid anchors of these chains can diffuse away from the contact zone.
Similar content being viewed by others
Notes
This fusion-release step typically occurs within endosomes, the inner monolayer of which is derived from the external monolayer of the plasma membrane. The latter contains only small amounts of anionic phospholipids but does have a significant negative charge due to glycoprotein, with smaller contributions from glycolipids. A larger distance between the bilayer and the charge plane of the proteins which project out from the surface of the bilayer would considerably reduce the linkage of those charges to the bilayer. On the other hand, changes in environmental conditions can lead to changes in exposure of the anionic phosphatidylserine which favor fusion with N-[1-(2,3-dioleoyloxy)propyl]-N,N,N-trimethylammonium (DOTAP) lipoplexes, as shown by Stebelska, Wyrozumska & Sikorski (2006).
References
Allen TM, Austin GA, Chonn A, Lin L, Lee KC (1991a) Uptake of liposomes by cultured mouse bone marrow macrophages: influence of liposome composition and size. Biochim Biophys Acta 1061:56–64
Allen TM, Hansen C, Martin F, Redemann C, Yau-Young A (1991b) Liposomes containing synthetic lipid derivatives of poly(ethylene glycol) show prolonged circulation half-lives in vivo. Biochim Biophys Acta 1066:29–36
Brunger AT (2001) Structural insights into the molecular mechanism of calcium-dependent vesicle-membrane fusion. Curr Opin Struct Biol 11:163–173
Chanturiya A, Scaria P, Woodle MC (2000) The role of membrane lateral tension in calcium-induced membrane fusion. J Membr Biol 176:67–75
Chanturiya A, Scaria P, Kuksenok O, Woodle MC (2002) Probing the mechanism of fusion in a two-dimensional computer simulation. Biophys J 82:3072–3080
Chou T, Jaric MV, Siggia ED (1997) Electrostatics of lipid bilayer bending. Biophys J 72:2042–2055
De Gennes PG (1980) Conformations of polymers attached to an interface. Macromolecules 13:1069–1075
Garcia RA, Pantazatos SP, Pantazatos DP, MacDonald RC (2001) Cholesterol stabilizes hemifused phospholipid bilayer vesicles. Biochim Biophys Acta. 1511:264–270
Jacobson K, Ishihara A, Inman R (1987) Lateral diffusion of proteins in membranes. Annu Rev Physiol 49:163–75
Jahn R, Scheller RH (2006) SNAREs—engines for membrane fusion. Nat Rev Mol Cell Biol 7:631–643
Klibanov AL, Maruyama K, Torchilin VP, Huang L (1990) Amphipathic polyethyleneglycols effectively prolong the circulation time of liposomes. FEBS Lett 268:235–237
Korlach J, Schwille P, Webb WW, Feigenson GW (1999) Characterization of lipid bilayer phases by confocal microscope and fluorescence correlation spectroscopy. Proc Natl Acad Sci USA 96:8461–8466
Kozlov MM, Markin VS (1984) On the theory of membrane fusion. The adhesion–condensation mechanism. Gen Physiol Biophys 5:379–402
Lei G, MacDonald RC (2003) Lipid bilayer vesicle fusion: intermediates captured by high-speed microfluorescence spectroscopy. Biophys J 85:1585–1599
Lentz BR, Malinin V, Haque ME, Evans K (2000) Protein machines and lipid assemblies: current views of cell membrane fusion. Curr Opin Struct Biol 10:607–615
MacDonald RC (1988) Mechanisms of membrane fusion in acidic lipid-cation systems. In: Ohki S, Doyle D, Flanagan TD, Hui SW, Mayhew E (eds) Molecular mechanisms of membrane fusion. Plenum Press, New York, pp 101–112
MacDonald RC, Gorbonos A, Mornsen MM, Brockman HL (2006) Surface properties of dioleoyl-sn-glycerol-3-ethylphosphocholine, a cationic phosphatidylcholine transfection agent, alone and in combination with lipids or DNA. Langmuir 22:2770–2779
Marsh D, Bartucci R, Sportelli L (2003) Lipid membranes with grafted polymers: physicochemical aspects. Biochim Biophys Acta 1615:33–59
Martin I, Ruysschaert JM (2000) Common properties of fusion peptides from diverse systems. Biosci Rep 20:483–500
Maruyama K, Yuda T, Okamoto A, Ishikura C, Kojima S, Iwatsuru M (1991) Effect of molecular weight in amphipathic polyethylene glycol on prolonging the circulation time of large unilamellar liposomes. Chem Pharm Bull (Tokyo) 39:1620–1622
Mori A, Klibanov AL, Torchilin VP, Huang L (1991) Influence of the steric barrier activity of amphipathic polyethylene glycol and ganglioside GM1 on the circulation time of liposomes and on the target binding of immunoliposomes in vivo. FEBS Lett 284:263–266
Needham D, Nunn RS (1990) Elastic deformation and failure of lipid bilayer membranes containing cholesterol. Biophys J 58:997–1009
Niles WD, Silvius JR, Cohen FS (1996) Resonance energy transfer imaging of phospholipid vesicle interaction with a planar phospholipid membrane: undulations and attachment sites in the region of calcium-mediated membrane–membrane adhesion. J Gen Physiol 107:329–351
Noppl-Simson DA, Needham D (1996) Avidin–biotin interactions at vesicle surfaces: adsorption and binding, cross-bridge formation, and lateral interactions. Biophys J 70:1391–1401
Pantazatos DP, MacDonald RC (1999) Directly observed membrane fusion between oppositely charged phospholipid bilayers. J Membr Biol 170:27–38
Reynier P, Briane D, Coudert R, Fadda G, Bouchemal N, Bissieres P, Taillandier E, Cao A (2004) Modifications in the head group and in the spacer of cholesterol-based cationic lipids promote transfection in melanoma B16-F10 cells and tumours. J Drug Target 12:25–38
Safinya CR, Ewert K, Ahmad A, Evans HM, Raviv U, Needleman DJ, Lin AJ, Slack NL, George C, Samuel CE (2006) Cationic liposome–DNA complexes: from liquid crystal science to gene delivery applications. Philos Trans A Math Phys Eng Sci 364:2573–2596
Soong R, Macdonald PM (2005) Lateral diffusion of PEG-lipid in magnetically aligned bicelles measured using stimulated echo pulsed field gradient 1H NMR. Biophys J 88:255–268
Stebelska K, Wyrozumska P, Sikorski AF (2006) PS exposure increases the susceptibility of cells to fusion with DOTAP liposomes. Chem Biol Interact 160:165–174
Tenchov B, MacDonald RC (2005) Fluorescent label effects on giant unilamellar vesicles (GUV)—transient pore formation and membrane area reduction. Biophys J 88:416A
Tirosh Y, Barenholz Y, Katzhendler Y, Priev A (1998) Hydration of polyethylene glycol-grafted liposomes. Biophys J 74:1371–1379
Visser CC, Stevanovic S, Voorwinden LH, van Bloois L, Gaillard PJ, Danhof M, Crommelin DJA, de Boer AG (2005) Targeting liposomes with protein drugs to the blood–brain barrier in vitro. Eur J Pharm Sci 25:299–305
Woodle MC, Lasic DD (1992) Sterically stabilized liposomes. Biochim Biophys Acta 1113:171–199
Yoshida A, Hashizaki K, Yamauchi H, Sakai H, Yokoyama S, Abe M (1999) Effect of lipid with covalently attached poly(ethylene glycol) on the surface properties of liposomal bilayer membranes. Langmuir 15:2333–2337
Acknowledgements
Supported by NIH grants GM52329, GM57305, and the Center for Cancer Nanotechnology Excellence (CCNE) initiative of the National Institutes of Health’s National Cancer Institute under Award Number U54CA119341.
Author information
Authors and Affiliations
Corresponding author
Rights and permissions
About this article
Cite this article
Lei, G., MacDonald, R.C. Effects on Interactions of Oppositely Charged Phospholipid Vesicles of Covalent Attachment of Polyethylene Glycol Oligomers to Their Surfaces: Adhesion, Hemifusion, Full Fusion and “Endocytosis”. J Membrane Biol 221, 97–106 (2008). https://doi.org/10.1007/s00232-007-9089-x
Received:
Accepted:
Published:
Issue Date:
DOI: https://doi.org/10.1007/s00232-007-9089-x