54:, often the composition of the phospholipids is different between the inner and outer leaflets. Phosphatidylcholine, phosphatidylethanolamine, phosphatidylserine, phosphatidylinositol, and sphingomyelin are some of the most common lipids most animal cell membranes. These lipids are widely different in charge, length, and saturation state. The presence of unsaturated bonds (double bonds) in lipids for example, creates a kink in acyl chains which further changes the lipid packing and results in a looser packing. Therefore, the composition and sizes of the unilamellar liposomes must be chosen carefully based on the subject of the study.
42:
20–100 nm, large unilamellar liposomes/vesicles (LUVs) with a size range of 100–1000 nm and giant unilamellar liposomes/vesicles (GUVs) with a size range of 1–200 μm. GUVs are mostly used as models for biological membranes in research work. Animal cells are 10–30 μm and plant cells are typically 10–100 μm. Even smaller cell organelles such as mitochondria are typically 1–2 μm. Therefore, a proper model should account for the size of the specimen being studied. In addition, the size of vesicles dictates their
117:
with certain frequency and voltage is applied which promotes formation of GUVs. For polyunsaturated lipids, this technique can induce a significant oxidation effect on the vesicles. Nevertheless, it is a very common and reliable technique to generate GUVs. Modified approaches exist that employ gel-assisted swelling (agarose-assisted swelling or PVA-assisted swelling) for the formation of GUVs under more biologically relevant conditions.
104:(for instance with 1 second pulses in 3 Hz cycles at a power of 150 W) or by extrusion. In extrusion method, the lipid mixture is passed through a membrane for 10 or more times. Depending on the size of the membrane, either SUVs or LUVs can be obtained. Keeping vesicles under argon and away from oxygen and light can extend their lifetime.
112:
Natural swelling: in this method soluble lipids in chloroform are pipetted on a Teflon ring. The chloroform is allowed to evaporate and the ring is then placed under the vacuum for several hours. Next the aqueous buffer is added gently over the Teflon ring and lipids are allowed to naturally swell to
99:
can be used to form a homogeneous layer of liposomes. This step removes the bulk of chloroform. To remove the residues of trapped chloroform, lipids are placed under vacuum from several hours to overnight. Next step is re-hydration where the dried lipids are re-suspended in the desired buffer. Lipids
116:
Electroformation: In this method lipids are placed on a conductive cover glass (indium tin oxide or ITO coated glass) or on Pt wires instead of a Teflon ring and after vacuuming, buffer is placed on the dried lipids and it is sandwiched using a second conductive cover glass. Next an electrical field
120:
A variety of methods exist to encapsulate biological reactants within GUVs by using water-oil interfaces as a scaffold to assemble lipid layers. This allows the use GUVs as cell-like membrane containers for the in vitro recreation (and investigation) of biological functions. These encapsulation
41:
or a mixture of such lipids, containing aqueous solution inside the chamber. Unilamellar liposomes are used to study biological systems and to mimic cell membranes, and are classified into three groups based on their size: small unilamellar liposomes/vesicles (SUVs) that with a size range of
94:
lipids. In the case of lyophilized lipids, they can be solubilized in chloroform. Lipids are then mixed with a desired molar ratio. Then chloroform is evaporated using a gentle stream of nitrogen (to avoid oxygen contact and oxidation of lipids) at room temperature. A
162:
In biomedical research, unilamellar liposomes are extremely useful to study biological systems and mimicking cell functions. As a living cell is very complicated to study, unilamellar liposomes provide a simple tool to study membrane interaction events such as
46:
which is an important factor in studying fusion proteins. SUVs have a higher membrane curvature and vesicles with high membrane curvature can promote membrane fusion faster than vesicles with lower membrane curvature such as GUVs.
698:
Noyhouzer T, L'Homme C, Beaulieu I, Mazurkiewicz S, Kuss S, Kraatz HB, et al. (May 2016). "Ferrocene-Modified
Phospholipid: An Innovative Precursor for Redox-Triggered Drug Delivery Vesicles Selective to Cancer Cells".
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There are several methods to prepare unilamellar liposomes and the protocols differ based on the type of desired unilamellar vesicles. Different lipids can be bought either dissolved in
155:, and thus drugs can be targeted to these cells. For general or overall delivery, SUVs may be used. For topical applications on skin, specialized lipids like phospholipids and
50:
The composition and characteristics of the cell membrane varies in different cells (plant cells, mammalian cells, bacterial cells, etc). In a membrane
73:(MLVs), consist of many concentric amphiphilic lipid bilayers analogous to onion layers, and MLVs may be of variable sizes up to several micrometers.
515:
Zhou Y, Berry CK, Storer PA, Raphael RM (February 2007). "Peroxidation of polyunsaturated phosphatidyl-choline lipids during electroformation".
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can be vortexed for several minutes to insure that all the lipid residues get re-suspended. SUVs can be obtained in via two methods. Either by
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form GUVs overnight. the disadvantage of this method is that a large amount of multilamellar vesicles and lipid debris are formed.
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17:
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may be used to make drug-free liposomes as moisturizers, and with drugs such as for anti-ultraviolet radiation applications.
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745:
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methods include microfluidic methods, which allow for a high-yield production of vesicles with consistent sizes.
268:"Giant unilamellar vesicles - a perfect tool to visualize phase separation and lipid rafts in model systems"
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of these liposomes. If injected into circulation of human/animal body, MLVs are preferentially taken up
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Litschel T, Schwille P (March 2021). "Protein
Reconstitution Inside Giant Unilamellar Vesicles".
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Alberts B, Johnson A, Lewis J, Raff M, Roberts K, Walter P (2002). "The Lipid
Bilayer".
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649:"Creation of Artificial Cell-Like Structures Promoted by Microfluidics Technologies"
385:"Lipid composition of cell membranes and its relevance in type 2 diabetes mellitus"
309:"SNAREpin/Munc18 promotes adhesion and fusion of large vesicles to giant membranes"
129:
552:"Production of Isolated Giant Unilamellar Vesicles under High Salt Concentrations"
433:"Preparing Large, Unilamellar Vesicles by Extrusion (LUVET) | Avanti Polar Lipids"
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458:"Comparison of Extruded and Sonicated Vesicles for Planar Bilayer Self-Assembly"
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Proceedings of the
National Academy of Sciences of the United States of America
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217:"Liposomes and polymersomes: a comparative review towards cell mimicking"
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167:, protein localization in the plasma membrane, study ion channels, etc.
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38:
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Stein H, Spindler S, Bonakdar N, Wang C, Sandoghdar V (2017).
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drugs can be carried as solution inside the SUVs or MLVs and
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Wesołowska O, Michalak K, Maniewska J, Hendrich AB (2009).
307:
Tareste D, Shen J, Melia TJ, Rothman JE (February 2008).
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Small unilamellar vesicles and large unilamellar vesicles
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Cho NJ, Hwang LY, Solandt JJ, Frank CW (August 2013).
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34:, bounded by a single bilayer of an
529:10.1016/j.biomaterials.2006.10.016
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647:Sato Y, Takinoue M (March 2019).
147:drugs can be incorporated into
18:Vesicle (biology and chemistry)
1:
383:Weijers RN (September 2012).
369:Molecular Biology of the Cell
713:10.1021/acs.langmuir.6b00511
606:Annual Review of Biophysics
69:, in general. In contrast,
61:structure is comparable to
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401:10.2174/157339912802083531
108:Giant unilamellar vesicles
15:
244:21.11116/0000-0002-1554-8
569:10.3389/fphys.2017.00063
389:Current Diabetes Reviews
272:Acta Biochimica Polonica
221:Chemical Society Reviews
556:Frontiers in Physiology
334:10.1073/pnas.0712125105
71:multilamellar liposomes
285:10.18388/abp.2009_2514
65:lipid organization in
741:Drug delivery devices
135:are used as targeted
67:biological membranes
24:unilamellar liposome
756:Colloidal chemistry
474:2013Mate....6.3294C
437:Avanti Polar Lipids
325:2008PNAS..105.2380T
666:10.3390/mi10040216
234:10.1039/C8CS00162F
177:Lipid polymorphism
44:membrane curvature
483:10.3390/ma6083294
227:(23): 8572–8610.
215:(November 2018).
97:rotary evaporator
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125:Applications
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751:Surfactants
612:: 525–548.
278:(1): 33–9.
145:hydrophobic
141:Hydrophilic
92:lyophilized
77:Preparation
36:amphiphilic
735:Categories
659:(4): 216.
442:2018-10-29
193:References
102:sonication
88:chloroform
16:See also:
634:232131463
462:Materials
139:systems.
133:liposomes
721:26987014
701:Langmuir
685:30934758
626:33667121
588:28243205
537:17107709
502:28811437
419:22698081
353:18268324
294:19287805
253:30177983
182:Liposome
171:See also
28:liposome
676:6523379
579:5303729
493:5521307
470:Bibcode
410:3474953
344:2268145
321:Bibcode
52:bilayer
32:vesicle
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562:: 63.
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90:or as
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57:Each
39:lipid
717:PMID
681:PMID
622:PMID
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533:PMID
498:PMID
415:PMID
349:PMID
290:PMID
249:PMID
30:, a
709:doi
671:PMC
661:doi
614:doi
574:PMC
564:doi
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488:PMC
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317:105
280:doi
239:hdl
229:doi
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