BIOL 201 Lecture Notes - Lecture 14: Liposome, Dispersity, Lecithin

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Published on 9 Feb 2013
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Liposomes, which use a form nanotechnology science, also impressively and harmoniously, use
the generalized nature of the liposomes themselves to increase the efficacy, bioavailability,
absorption, and delivery of these certain entrapped dietary and nutritional supplements. The
generalized nature and makeup of phospholipid composed liposomes adroitly complement the
natural lining of nearly every cell within the human body. This therefore creates a natural bond
and or affinity for the liposomes to deliver their onboard “payload” to the cells. The quality of
rawLipid used in the preparation and manufacturing of the liposomes therefore precisely co-
relates to this natural congruency between the liposomes and the cells of the human body.
The correct choice of liposome preparation method depends on the following parameters:
1. the physicochemical characteristics of the material to be entrapped and those of the
liposomal ingredients;
2. the nature of the medium in which the lipid vesicles are dispersed
3. the effective concentration of the entrapped substance and its potential toxicity;
4. additional processes involved during application/delivery of the vesicles;
5. optimum size, polydispersity and shelf-life of the vesicles for the intended application;
and,
6. batch-to-batch reproducibility and possibility of large-scale production of safe and
efficient liposomal products
Formation of liposomes and nanoliposomes is not a spontaneous process. Lipid vesicles are
formed when phospholipids such as lecithin are placed in water and consequently form one
bilayer or a series of bilayers, each separated by water molecules, once enough energy is
supplied. Liposomes can be created by sonicating phospholipids in water. Low shear rates create
multilamellar liposomes, which have many layers like an onion. Continued high-shear sonication
tends to form smaller unilamellar liposomes. In this technique, the liposome contents are the
same as the contents of the aqueous phase. Sonication is generally considered a "gross" method
of preparation as it can damage the structure of the drug to be encapsulated. Newer methods such
as extrusion and Mozafari method are employed to produce materials for human use.
Further advances in liposome research have been able to allow liposomes to avoid detection by
the body's immune system, specifically, the cells of reticuloendothelial system (RES). These
liposomes are known as "stealth liposomes", and are constructed with PEG (Polyethylene
Glycol) studding the outside of the membrane. The PEG coating, which is inert in the body,
allows for longer circulatory life for the drug delivery mechanism. However, research currently
seeks to investigate at what amount of PEG coating the PEG actually hinders binding of the
liposome to the delivery site. In addition to a PEG coating, most stealth liposomes also have
some sort of biological species attached as a ligand to the liposome in order to enable binding via
a specific expression on the targeted drug delivery site. These targeting ligands could
be monoclonal antibodies(making an immunoliposome), vitamins, or specific antigens. Targeted
liposomes can target nearly any cell type in the body and deliver drugs that would naturally be
systemically delivered. Naturally toxic drugs can be much less toxic if delivered only to diseased
tissues. Polymersomes, morphologically related to liposomes, can also be used this way.
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