Different Methods Of Liposome Manufacturing

By Jody Leach


Liposomes have attracted much attention since they were first discovered. These artificially created, microscopic spheres have many properties that make them extremely useful. One of these is their bio-compatibility. They act in exactly the same way as the cellular membranes of the body. This means they can be used as a unique delivery system for nutrients, drugs and other agents to specific areas in an organism. There are a numbers of ways in which liposome manufacturing is achieved, all of which have advantages and disadvantages.

When phosphlipids such as lecithin come into contact with water, an interesting effect occurs. The molecules consist of a head which loves water and two tails that repel it. This means that the heads all face one side and the tails the other. Another layer is formed with tails all facing the tails of the first later and the heads facing the other way. These layers form the membranes around and inside every cell of the human body.

Liposomes can be used as delivery vehicles for a wide variety of drugs, vaccines, enzymes, genetic material and for some nutritional supplements as well. They not only allow for release of encapsulated materials but are beneficial in themselves for cells. The lipids used to construct the fatty part of the molecule is used by the cell wall for repair and construction of new membranes.

All liposomes consist of a lipid bilayer encapsulating a payload of therapeutic molecules. They bypass the digestive tract, so the payload remains biologically inert until such stage as the cell membrane ruptures. The difference between liposomes comes in the way, how, when and where that occurs.

Liposomes are usually synthesized by mixing and dissolving phospholipids in organic solvent. A clear lipid film is formed by removing the solvent. Hydration of this film eventually leads to formation of large vesicles which have several layers, much like the structure of an onion. Each bilayer is separated from the other by water. A form of energy is required to reduce their size. Sonication, agitation by sound waves, is one method used and extrusion is another.

Liposomes are actually fairly simple to make, not requiring complex materials, equipment or methods. Each method and technique offers certain benefits and has some failings. Sonication can cause structural changes to what is entrapped. Liquid hydration methods do not produce a high payload.

Some of the problems associated with these processes are inconsistencies in size, structural instability and high costs. These problems are all receiving attention and solutions are being found. Cosmetology, for example, is benefiting from the production of tiny particles called nanosomes which are much, much smaller than normal liposomes and can therefore penetrate the skin more easily.

Although conventional methods of manufacture are effective, research continues apace to make them more so. Much research is being conducted into ways in which liposomes can be created that have a strong chemical affinity for the cells of a particular organ or kind of tissue. They also need to have the ability to deliver payloads to the cells as efficiently as possible.




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