Bilayer vesicles encapsulation

Injection, Suspension, Liposomal A liquid preparation, suitable for injection, which consists of an oil phase dispersed throughout an aqueous phase in such a manner that liposomes (a lipid bilayer vesicle usually composed of phospholipids which is used to encapsulate an active drug substance, either within a lipid bilayer or in an aqueous space) are formed. 

Lipid bilayers are formed by many amphiphilic molecules in the presence of water. Their interest derives not only from the fact that they are a major, if not the only, organizing principle of biological membranes (1), but also because they tend to form closed (usually) spherical structures (liposomes or lipid bilayer vesicles) in which inner and outer aqueous spaces are separated by the lipid bilayers (2) which thereby provides a means of encapsulation (3, 4). 

Encapsulation Processes by Bilayer Vesicles 423 Mean Curvature... 

In this brief review we will describe some important encapsulation processes by vesicular aggregates. Encapsulation will be broadly interpreted. Apart from solubilization in the aqueous pool inside the vesicle, the term will also encompass binding of solubilizates to all binding sites available in the vesicular system. We will not discuss bilayer vesicles formed from amphiphiles further functionalized by receptor molecules, such as amphiphilic cyclodextrins. ... 

Interesting and practically relevant materials for stud5dng the behavior of smart polymers attached to lipid membranes are liposomes, self-assembled 50-200 nm vesicles that have one or more (phospho)lipid bilayers which encapsulate a fraction of the solvent. Liposomes are stable in aqueous suspension because of the repulsive forces that appear when two liposomes approach each other. Liposomes are widely used for drug delivery and in cosmetics (96). 

Sustained Release. Depending on permeation coefficient, vesicle radius, and bilayer thickness, encapsulated low molecular weight solutes will be released on timescales of minutes to days. This can be used for the controlled release of drugs, where the dose can be predicted from the encapsnlated volume and the initial drug concentration in the vesicle using eqnation 21. Large ionic solutes, in particular proteins, will have low release rates and are practically permanently encapsulated until the vesicle is ruptured. 

In addition to encapsulation within the aqueous phase of vesicles, amphiphilic and lipophilic compounds can interact with the bilayer. 

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