Techniques And Methods For Liposome Manufacturing

By Jody Leach


The discovery of liposomes with their many interesting properties has attracted much attention. These tiny spheres are suitable for using as delivery vehicles for nutrients and drugs into the human body. Identical to human cell membranes, they easily transfer and deliver active ingredients. Liposome manufacturing involves the same basic steps but the use many different techniques. Research is constantly being done to increase their effectiveness.

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 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.

Various lipids and mixtures can be used to make liposomes and some of these are of a higher quality than others. What they have in common is they do not go through the digestive tract and the encapsulated payload is not biologically active until it reaches the cells. It is how, when, where and why the rupture of the membrane occurs that the difference between them comes in.

The methods used in preparation may all be quite different but the basic stages remain the same. Thin lipid films are hydrated and this causes liquid bilayers to form. These large vesicles need to be reduced in size and energy output is required for this. Sonication is the use of sound waves and another mechanical method used is extrusion.

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.

A great benefit involved in using liposomes is that they can be customized for different applications by varying the method of preparation, size, lipid content and surface charge. Many conventional techniques for preparing them and reducing their size are fairly simple to implement and equipment does not have to be too sophisticated. However, novel routes are being discovered for preparation due to motivation to scale-down for point-of-care applications or or to scale-up for industrial applications.




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