liposomes

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Liposomes:

Liposomes PRESENTED BY M.RANJEETH KUMAR

LIPOSOMES:

LIPOSOMES INTRODUCTION Liposome was discovered about 40 years ago by Bangham and co-workers. Liosomes are microscopic vesicles composed of a bilayer of phospholipids or any similar amphipathic lipids (Remington et a., 2000). Liposomes vary incharge and size depending on the method of preparation and the lipids used the multi lamellar vesicle [MLV] size range is 0.1 to 5.0 micrometers. The small unilamellar vesicle [SUV] size range is 0.02 to 0.05 micrometers and large unilamellar vesicle [LUV] size range varies from 0.06 micrometre and greater (lasic DD et al .,1990 ). Liposomes are drug carrying vesicles containing concentric phospholipid bilayers circulating around aqueous compartment ranging from 50-1000 nm in diameter. Various drugs from low molecular weight (glucose, synthetic drugs, etc.) to high molecular weight (peptides and proteins, DNA, etc.) have been incorporated in liposomes.

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LIPOSOMES DEFINITION Liposomes are defined as structure consisting of one or more concentric spheres of lipid bilayers separated by water or aqueous buffer compartments. ( Or) liposomes are simple microscopic vesicles in which an aqueous volume is entirely enclosed by a membrane composed of lipid bilayer .

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ADVANTAGES 1.It provides controlled drug delivery 2.Liposome should be bio degradable, bio compatible , and flexible. 3.It should be non ionic. 4.It can carry both water and lipid soluble drugs. 5.It should be improve the protein stabilization it provides controlled hydration. 6.It provide sustained release. 7.It provides targeted drug delivery or site specific drug delivery.

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. DISADVANTAGES 1.Liposomes are having low solubility. 2.It is less stability. 3.It is short half life. 4.The phospholipids undergoes oxidation, hydrolysis. 5.Leakage and fusion. 6.t is high production cost . l.

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LIPOSOMES BASIC COMPONENTS OF LIPOSOMES A. Phospholipids The most common natural phospholipid is the phospatidylcholine (PC) is the amphipathic molecule and also known as lecithin. Naturally occurring phospholipids used in liposomes are: Phosphatidylcholine Phosphatidylethanolamine Phosphatidylserine Synthetic phospholipids used in the liposomes are: Dioleoyl phosphatidylcholine Disteroyl phosphatidylcholine Dioleoyl phosphatidylethanolamine Distearoyl phosphatidylethanolamine

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Phosphatidylcholine is an amphipathic molecule in which exists A hydrophilic polar head group, phosphocholine. A glycerol bridge A pair of hydrophobic acyl hydrocarbon chains

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B. Cholestrol Cholesterol can be incorporated into phospholipids membrane in very high concentration up to 1:1 or 2:1 molar ratios of cholesterol to phospatidylcholine. Being an amphipathic molecule, cholesterol inserts into the membrane with its hydroxyl group of cholesterol oriented towards the aqueous surface and aliphatic chain aligned parallel to the acyl chains in the center of the bilayers and also it increase the separation between choline head groups and eliminates the normal electrostatic and hydrogen bonding interaction.

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Over all composion

LIPOSOMES:

LIPOSOMES PREPARATION OF UVs BY PHYSICAL METHODS A. SONICATED SUVs The Small unilamellar vesicles(SUVs) are produced from MLVs by exposing the MLVs to ultrasonic irradiation. The production can be achieved by the following sonicators. 1.Bath type sonicator: The arrangement of sonicator is used for the processing large volumes of diluted lipids an inert atmosphere in the sonicator is maintained by means of sonicator nitrogen or organ.

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LIPOSOMES BATH TYPE SONICATOR

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LIPOSOMES Probe sonicator: It is for rapid processing of small volumes of lipids with high energy. It also utilizes nitrogen gas and ice bath.

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LIPOSOMES B) Small Unilamellar Liposomes (SUV) (i) Sanitation Method (ii) French Pressure Cell Method

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LIPOSOMES C) Large Unilamellar Liposomes (LUV) They have high internal volume/encapsulation efficiency and are now a day’s being used for the encapsulation of drugs and macromolecules. (i) Solvent Injection Methods (a) Ether Infusion Method (b) Ethanol Injection Method (ii) Detergent Removal Methods (iii) Reserves Phase Evaporation Method (iv) Freeze-Thaw Method (C) Giant Liposomes (D) Multivesicular Liposomes

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LIPOSOMES 8).Evaluation of Liposomes Physical Properties 1.Partical size Both particle size and particle size distribution of liposomes influence their physical stability. These can be determined by the following methods. (a) Laser Light Scattering Proton correlation spectroscopy measures the fluctuations in the scattered light, caused due to the Brownian motion of particles in liposomal suspension. It involves the Stokes-Einstein equation D= kT /6nRh

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Where, D=Translational diffusion coefficient K=Boltzmann constant T=Absolute temperature n=Viscosity of solvent Rh=Mean hydrodynamic radius 2. Surface Charge The method involved in the measurement of surface charge is based on free-flow electrophoresis of MLVs. 3.Percent Drug Entrapment Determination of the quantity of drug encapsulated in the liposomes helps to estimate the behaviour of drug in biological systems. However, the initial step is to remove any free drug i.e, encapsulated drug fraction from the sample.

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4.Phase Behaviour : Liposomes at transition temparature(T c) undergo reversibe phasetransition i.e.the plor head groups in gel state become disordered to form the liquid crytalline state. 5.Drug Release Rate: the rate if drug release from the liposomes can be determined by invitro assays which helps to predict the pharmacokinetics and bio –ava libility of the drug. However quantitative in vivo studies are found to be more complete aline state.

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LIPOSOMES Chemical Properties 1.Determination of phospholipids: The phospholipid content of liposomes can be determined indirectly by two assays ,Bartlett assay and steward assay. Barlett assay: This method of determining the phospholipids is very sensitive and may produce erroneous results in the presence a of even trace of amounts of inorganic phosphate.Therefore , borosilicate glass tubes and double distiilled water is used . Steward Assay : This assay overcomes the drawbacks of bartlett , assay but cannot used to evaluate those samples which contains the mixtures of unknown phospholipids .

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LIPOSOMES 2. Cholesterol analysis : (a) Qualitative analysis Performed using a capillary column filled with fused silica. Quantitative analysis The sample is reacted with a reagent and the absorbance of purple coloured complex is measured at 610nm.

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Applications 1.Liposomes offer a great use in all the fields of science and medicine. Especially in Bio technology considering the targeted action. 2.Liposomes have their application in the many fields of medicine like diagnosis and therapy. 3.Liposomes have their application in cosmetic industry wider than any other field. 4.Liposomal application in fermentation technology has yielded better results in the production of cheese, enzymes, antibiotics, etc. 5.Even agro-food industry employs liposome's in application to herbicides and pesticides by adopting the sustained release from the liposome's.

liposomes:

liposomes Conclusion: From the above article it is concluded that the consideringstheadvan-tages of this novel drug delivery system. A novel technology has been developed by which water soluble subtances can be sloubilized in the absence of water in to oils. The Formation of anhydrous revers micelles might play an important role in the solubilizationAnd the resulting oil solution are physically and chemically stable. Two types of formula- tion are developed. On exposureto water, a substantial amount of drug can be released From type 1 formulations in theliposome-entrapped fromtherefore, type1formulation Can be used as lipiddepot drug delivery system. In contrast, type 2 formulation are self-Emulsifying drug delivery system and might find application in oral deliverpeptides/Proteins. Liposomes also its modification or upgrade versions like enzymosomes, viro- Somes, hemosomes, erytrosomes etc.

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REFERENCES Alpes H., Allmann K., Plattner H., Reichert J., Rick R. and Schulz S. (1986). Biochim. Biophys. Acta. 862 : 294. Bangham A.D., Standish M.M. and Watlins J.C. (1965). J. Mol. Biol. 13 : 238. Bangham A.D., Hill M.W. and Miller N.G.A. (1974). In : Methods in Membrane Biology. Batzri S. and Kprn E.D (1973). Biochim. Biophys. Acta. 298 : 1015. Cestaro B., Pistolesi E., Hershkowitz N. and Galt S. (1982). Biochim. Biophys. Acta. Chu Chun-Jung and Szoka C. Jr. (1994). J. Liposome Res. 361. Crow J.H., Spargo B.J. and Crow L.M. (1987). Proc. Natl. Acad. Sci. USA. 84 : 1537. Cullis R.P., Hope M.J., Bally M.B., Madden T.D and Janoff AS. (1987). In : liposome fromBiophysics to Therapeutics (Ostro M.J., Ed.) Marcel Dekker, N.Y., Chapter 2, p.39.

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Thank You 

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