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.

Formation of liposomes is not spontaneous. Lipid vesicles are formed when phospholipids like lecithin are placed in water. Each molecule has a water-loving head and two water-repelling tails. When these molecules are placed in a water-based solution, the heads line up side by side with the tails behind. The fact that the tails are repelled by water means that another layer lines up with the tails facing one another. These two rows form a protective membrane around the cell.

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.

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.

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.

So, the general elements consist of lipid preparation for hydration, hydration with agitation and then sizing of vesicles. Each different method used has certain advantages and disadvantages. Liquid hydration methods usually result in low dose loading. Sonication can affect the structure of an encapsulated drug.

The type of manufacturing processes and equipment used both have an effect on the type of liposomes produced. Inconsistent sizes, high production costs and structural instability are just some of the challenges faced in production. Many advances are being made in this respect as research proceeds at a rapid pace. An exciting example is research into how to make liposomes that can target certain organs or diseased tissue.

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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