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.

Phospholipids like lecithin is used as raw material. The phospholipid molecules have heads that love water. They also have two tails that are essential fatty acid chains repelled by water. When the phospholipids are put in a solution that is water-based, the heads end up side by side with the tails trailing behind. The fact that the tails repel water means that another layer lines up with the tails facing the tails of the first layer. This natural alignment results in two rows of tightly fitting molecules. These layers form membranes around and inside all cells.

Liposomes are used to deliver toxic drugs to target cancer cells. They are used for delivering nutrients deficient in the body or cosmetic nutrients to the skin. Many other medical applications are possible too such as in the field of genetics. Preparation methods depend on various factors such as the characteristics of the material to be carried, the consistency offered from batch to batch and scale of production.

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.

Different methods are known to have certain weaknesses and strengths. Some allow for high load dosing and others offer much lower dose loading. Some of them offer more consistency and stability. The encapsulated content is affected more by some methods than others.

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.

One of the greatest benefits of liposomes is there flexibility. They can be adapted in many different ways to suit different applications. Size, surface charge and lipid content can all be varied according to the techniques used. Conventional methods are effective but much experimentation is still being done. The future holds many new possibilities with the exciting developments taking place in this field.




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