Film rehydration

Form SUVs, as described in the protocol above, by thin film rehydration in 1-5 ml of 10 mM Tris, leaving a final concentration of 80 mM lipid (see Note 3). 

Solvent Free Preparation Methods (Film Rehydration, Electroformation). 139... 

The method of solid rehydration (bulk swelling) resembles the film rehydration method however, the amphiphile is directly hydrated as bulk powder. Therefore, longer or more vigorous agitation to completely hydrate the polymer is required [42,103,114],... 

For the solvent inversion method the whole block copolymer has to be completely dissolved in a solvent before polymersome formation is initiated. Once the solvent containing the dissolved polymer is poured into an excess of water, the hydrophobic block becomes insoluble and polymersome formation is induced. Here, the created vesicles are typically between 100 and 200nm in diameter. Besides solvent inversion, film rehydration also relies on dissolving the amphiphilic block copolymer in a solvent other than water, hi contrast to solvent inversion, the solvent is slowly evaporated during this method to produce a thin film of precipitated polymer at the wall of the jar used. Once the film is created, the jar is filled with water and the self-assembly starts from the precipitated polymer film. Eventually, polymersomes are formed and the film is totally removed. If the jar surface is chemically altered, vesicles of up to 20 pm can be achieved. Otherwise, film rehydration yields the same vesicle sizes as solvent inversioa... 

FIGURE 6.4 Mechanisms of polymersome formation from block copolymers. For solvent inversion, film rehydration, and electroformation, the polymCT is first dissolved in an organic solvent and polymersomes are initiated after water is added to the system. In contrast, pH-sensitive polymers are dissolved in acidic water and polymersomes are formed by switching to basic conditions. 

The encapsulation of a larger hydrophobic model substrate was successfully realized utilizing highly fluorescent QDs. The enclosing of these nanoparticles inside the PB-h-PEO polymersomes was performed only via the film rehydration procedure because the preferred dispersant of QDs, chloroform, is immiscible with water and therefore not suitable for the cosolvent method. The rehydration procedure for QDs was done analogously to that for the Nile Red samples. Afterwards, filtration through 0.45-pm filters ensured a smaller vesicle size regime, which is important for further characterization. Absorption and emission spectra indicated the presence of QDs in the vesicle solution after filtration (Fig. 65). 

A method resulting in improved encapsulation of aqueous phase by MLV is the so-called dehydration-rehydration procedure (Kirby and Gregoriadis, 1984 Shew and Deamer, 1985). The lipid (usually preformed liposomes) is dried (by either lyophilization or evaporation) in the presence of the aqueous solute to be entrapped, thus forming a mixed film with solute trapped between layers. Subsequent gradual rehydration with a minimum of aqueous phase leads to the formation of MLV with a high entrapment of the aqueous solutes added. 

Desizing by chemical decomposition is applicable to starch-based sizes. Since starch and its hydrophilic derivatives are soluble in water, it might be assumed that a simple alkaline rinse with surfactant would be sufficient to effect removal from the fibre. As is also the case with some other size polymers, however, once the starch solution has dried to a film on the fibre surface it is much more difficult to effect rehydration and dissolution. Thus controlled chemical degradation is required to disintegrate and solubilise the size film without damaging the cellulosic fibre. Enzymatic, oxidative and hydrolytic degradation methods can be used. 

The mixture of liposomes and macromolecules was first dried under nitrogen the two types of molecules formed a multilamellar film with sandwich structures. Larger liposomes, containing macromolecules (proteins or RNA) were formed on rehydration. This process could have occurred in hot regions of the young Earth with the help of the tidal rhythm of the oceans. 

Entrapment of plasmid DNA and/or protein into liposomes entails the preparation of a lipid film from which multilamellar vesicles and, eventually, small unilamellar vesicles (SUVs) are produced. SUVs are then mixed with the plasmid DNA and/or protein destined for entrapment and dehydrated. The dry cake is subsequently broken up and rehydrated to generate multilamellar dehydration-rehydration vesicles (DRV) containing the plasmid DNA and/or protein. On centrifugation, liposome-entrapped vaccines are separated from nonentrapped materials. When required, the DRV are reduced in size by microfluidization in the presence or absence of nonentrapped materials or by employing an alternative method (7) of DRV production, which utilizes sucrose (see below). 

As the first step, a Ni(II) metal complex of HPMA copolymer was formed and purified [35]. It was then mixed with protein solutions to form dried films, which were rehydrated to investigate the swelling profile and stimuli sensitivity. 

In order to prepare liposomes, the lipid preparation is dried at low temperature under an inert gas atmosphere (protect the lipid from oxidation). The lipid film is swollen with water or buffered aqueous solution and several freeze-thaw cycles are carried out to get optimal rehydration of the lipid. The rehydrated lipid preparation is filtered using membrane filters with defined pore size. After repeated filtration steps (extrusion) an unilamellar liposome preparation with a defined size distribution is obtained. Large unilamellar vesicles (LUV) are produced in this way. LUV s are about 100 nm in size the thickness of the lipid bilayer is about 4 nm. Even smaller liposomes can be derived from sonication (sonication probe or ultra-sonication bath). Separation of the prepared liposomes... 

The lipid film is rehydrated in 5 ml of lipid buffer to obtain 20 mg/ml lipid stock. 

Rehydrate the film with 1 ml of Buffer Hepes Glucose, to give a final concentration of 10-mM DOTAP/9-mM Choi. 

Rehydrate the lipid film with an aqueous solution to result in a concentration of 1 mg DOTAP per 10 ml, rehydration media (see Note 2). 

Liposomes are formed by rehydration of a lipid film at temperatures below 4°C. The substances to be entrapped are added to the aqneons solntion consequently, formation of vesicles and entrapment occur simultaneously. After this preparation period, inhibitor molecules are added to the external medium that block all enzymes that have not been entrapped, before the suspension is extruded through filters with appropriate pore sizes. One main drawback of this strategy is that it can only be applied with lipids that have their main transition temperature below 0°C. This technique has basically been applied for the synthesis of poly(Phe) in liposomes. ... 

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