Liposome

Liposome

A liposome is an artificially-prepared vesicle composed of a lipid bilayer. The liposome can be used as a vehicle for administration of nutrients and pharmaceutical drugs.

Liposomes were first described by British haematologist Dr Alec D Bangham in 1961 (published 1964), at the Babraham Institute, in Cambridge.

Fig: Liposome 

CHARACTERISTICS OF LIPOSOMES

The smallest artifical vesicles of spherical shape that can be produced from natural non-toxic phospholipids and cholesterol. Being fat bodies, they are microscopic and spherical lipid vesicles formed by a bilayer of lecithin molecules surrounding an aqueous core. Ideally, all the liposomes should be less than 100 nm in diameter.

USE OF LIPOSOMES

1. As drug carriers and loaded with a great variety of molecules, such as small drug molecules, proteins, nucleotides and even plasmids.

2. As carriers for lipophilic drugs like the anti-tumor drug NOAC by encapsulation

ADVANTAGES OF LIPOSOMES

1.Biocompatible, completely biodegradable,non-toxic,flexible. 

2.Reduced toxicity and increased stability of entrapped drug via encapsulation. (Amphotericin B, Taxol)

3.Increased efficacy and therapeutic index of drug (Actinomycin-D).

4.Reduce exposure of sensitive tissues to toxic drugs.

5.Alter the pharmacokinetic and pharmacodynamic property of drugs (reduced elimination, increased circulation life time).

DISAVANTAGES OF LIPOSOMES

1. Production cost is high

2. Leakage and fusion of encapsulated drug / molecules.

3. Sometimes phospholipid undergoes oxidation and hydrolysis like reaction.

4. Short half-life

5. Low solubility

6. Fewer stables

3. Anti-viral derivatives of AZT and ddC.

4. as to carry normal genes into a cell.

l  Pharmacy use

1. Controlled release and transfer of drugsand more recently by the cosmetic industry.

2. Versatile liposomes have been used in cancer therapy,

3. Gene manipulation.

4. Skin care

Food industry of Liposomal

1. As to encapsulate various ingredients;

       Such as, flavors, functional ingredients and vitamins.

2. in cheese making industry.

3. Liposomes are commonly used in ripening the cheese

Composition of liposome

Phospholipid:

     Phospholipid is the major component of the biological membrane; two types of phospholipids are used natural and synthetic phospholipids. The most common natural phospholipid is the phospatidylcholine (PC) is the amphipathic molecule and also known as lecithin.

Cholesterol:

     Incorporation of cholesterol in liposome bilayer can bring about big changes in the preparation of these membranes. It does not mean by itself form bilayer membrane structure, but can be incorporated into phospholipids membrane in very high concentration up to 1:1 or 2:1 molar ratios of cholesterol to phospatidylcholine .

Mechanism of Liposome

A liposome encapsulates a region of aqueous solution inside a hydrophobic membrane; dissolved hydrophilic solutes cannot readily pass through the lipids. Hydrophobic chemicals can be dissolved into the membrane, and in this way liposome can carry both hydrophobic molecules and hydrophilic molecules.

Manufacturing

l  The correct choice of liposome preparation method depends on the following parameters.the physicochemical characteristics of the material to be entrapped and those of the liposomal ingredients;

l  the nature of the medium in which the lipid vesicles are dispersed

l  the effective concentration of the entrapped substance and its potential toxicity;

l  additional processes involved during application/delivery of the vesicles;

l  optimum size, polydispersity and shelf-life of the vesicles for the intended application; and,

l  batch-to-batch reproducibility and possibility of large-scale production of safe and efficient liposomal products.

Pharmaceutical Applications of Liposomes

l  The liposomal formulation of doxorubicin.

l  Liposomes in Cancer Therapy

l  Liposomes in AIDS Therapy

l  Liposomes in Malaria Therap

l  Liposome in lung therapy

l  Liposomes in Dermatology and Cosmetology