Many researchers claim that that liposomes and nanoliposomes form spontaneously upon hydration of their ingredients. However, when we put lipid and phospholipid molecules (constituents of these vesicles) in an aqueous medium and wait for, let say ever, we can not see any bilayer vesicle even using high resolution microscopes. Any comments please?
Dear Mozafari,
Lipids when placed in water (aqueous solutions) will aggregate to form structures. Those structures may have many shapes and sizes [Pls see Ref
Silvius JR. In Phospholipid Handbook , Gregor C (ed). Marcel
Dekker: New York, 1993]. Liposome structures are one of the forms that may occur and these can be unilamelar or multilamelar.
In practice, liposome vesicles are formed in the lab by extrusion passing through a filter of a certain size. This will also help to normalize the size of the liposome population. I usually check the size of liposome by dynamic light scatering (DLS).
You can check the liposome vesicle protocol at the Avanti website (https://avantilipids.com/tech-support/liposome-preparation/).
Hope this helps,
Ana
Dear Dr Reis,
Many thanks for replying to my question. Although at first it may seem a simple fact, but looking at the biophysical aspect of the subject, particularly publications by the eminent scientist D.D. Lasic, I am somehow confused. He wrote in one of his publications:
Spontaneous formation of liposomes
Numerous papers claim erroneously that liposomes form spontaneously upon hydration of lipids. Without agitation, however, only few liposomes would form, caused by crystal defects and not to the spontaneity of liposome formation upon swelling of lipids. However, below, we shall show that this is exactly the feature that makes liposomes useful for drug encapsulation and delivery.
(in; Novel applications of liposomes Dan D. Lasic; TIBTECH JULY 1998 (VOL 16))
can you give me your views on this?
The lipids have to be dried under vacuum to form a film (preivously lipids should be completely dissolved in organic solvents). Then the film can be hydrated with water to form liposomes. Sometime you need higher temperature to hydrate the film properly.When you reach and omogenous solution, you have to pass it into a filter to obtain liposomes of the appropriate size you require.
Of course liposomes will form if you use fosfolipids... not just random polymers.
Regards
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