2. Outline
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liposomes
Basic liposome structure.
Structural Components of Liposomes
Advantages of liposomes.
Classification of liposomes.
Preparation of liposomes.
Evaluation of liposomes
Applications
3. • Liposomes are concentric bilayered vesicles in which an aqueous
core is entirely enclosed by a membranous lipid bilayer mainly
composed of natural or synthetic phospholipids.
• The size of a liposome ranges from some 20 nm up to several
micrometers.
Liposomes
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Liposome
4. • The lipid molecules are usually phospholipids- amphipathic
moieties with a hydrophilic head group and two hydrophobic tails.
• On addition of excess water, such lipid moieties spontaneously
originate to give the most thermodynamically stable conformation.
• In which polar head groups face outwards into the aqueous
medium, and the lipid chains turns inwards to avoid the water
phase, giving rise to double layer or bilayer lamellar structures.
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6. Lamella
A Lamella is a flat plate like structure that
appears during the formation of liposomes.
The phospholipids bilayer first exists as a
lamella before getting converted into
spheres.
Several lamella of phospholipids bilayers
are stacked one on top of the other during
formation of liposomes to form a
multilamellar structure.
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7. Structural Components of Liposomes
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The main
components
of liposomes
are
Phospholipids
Cholesterol
8. Phospholipids
Two type of
hydrolysis
(along with
their hydrolysis
product)
Phosphoglycerides
Sphingolipids
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• Phospholipids are the major structural components of
biological membranes such as the cell membrane.
9. Phosphatidylcholine
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• Most common phospholipids used is
phosphatidylcholine (PC).
• Phosphatidylcholine is an amphipathic
molecule in which exists:-
– a hydrophilic polar head group,
phosphocholine.
– a glycerol bridge.
– a pair of hydrophobic acyl hydrocarbon
chains.
11. Cholesterol
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Cholesterol by itself does not form bilayer structure.
Cholesterol act as fluidity buffer
After intercalation with phospholipid molecules alter the freedom of motion
of carbon molecules in the acyl chain
Restricts the transformations of trans to gauche conformations.
Cholesterol incorporation increases the separation between choline head
group & eliminates normal electrostatic & hydrogen bonding interactions
12. Advantages of liposomes
Provides selective passive targeting to tumor tissues.
Increased efficacy and therapeutic index.
Increased stability of encapsulated drug.
Reduction in toxicity of the encapsulated agent.
Site avoidance effect (avoids non-target tissues).
Improved pharmacokinetic effects (reduced elimination
increased circulation life times).
Flexibility to couple with site specific ligands to achieve
active targeting.
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13. Disadvantages Of liposomes
Physical/ chemical stability
Very high production cost
Drug leakage/ entrapment/ drug fusion
Sterilization
Short biological activity / t ½
Oxidation of bilayer phospholipids and low solubility
Rate of release and altered bio distribution
Low therapeutic index and dose effectiveness
Overcoming resistance
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14. Liposomes Evolution
• 1965 First description of closed lipid bilayer vesicles.
• 1967 introduction of the term liposomes to describe closed
lipid bilayer vesicles
• 1972 liposomes first used as delivery systems of drugs
• 1974 first patients to be injected with liposomes
• 1979 liposomes first used as delivery systems of nucleic
acids to cells
• 1980 first monoclonal anti body targeted liposomes termed
immuno liposomes
• 1987 first synthetic cationic liposomes deliver genes to cells
• 1987 first sterically stabilized long circulating liposomes
system introduced
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15. • 1992 first liposome based non viral vector gene therapy
clinical trail on cystic fibrosis patients.
• 1993 first liposome based vaccine against hepatitis A is
marketed.
• 1995 first long circulating immune liposomes.
• 1995 the liposomes encapsulated from of the anticancer drug
doxorubicin and daunorubicin approved for human use.
• 1997 first liposomes based DNA vaccine.
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16. Classification On the basis of structural parameters
Multilamellar vesicles (> 0.5 µm) MLV
Oligo lamellar vesicles (0.1-1 µm) OLV
Unilamellar vesicles (all size range) UV
Small Unilamellar vesicles (20-100 nm) SUV
Medium sized Unilamellar vesicles MUV
Large Unilamellar vesicles (> 100 µm) LUV
Giant Unilamellar vesicles (>1 µm) GUV
Multi vesicular vesicles (>1 µm) MVV
On the basis of liposome preparation:
Vesicles prepared by reverse phase evaporation method REV
Multi lamellar vesicle by REV MLV-REV
Stable plurilamellar vesicle SPLV
Frozen & thawed MLV FATMLV
Vesicles prepared by extrusion techniques VET
Dried reconstituted vesicles DRV 12
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17. Method of liposome preparation
Physical dispersion method:
1. Hand shaking MLVs
2. Non-shaking LUVs
3. Freeze drying
4. Pro-liposomes
To reduce liposome size:
1. Micro emulsification
2. Membrane extrusion
3. Ultrasonication
4. French pressure cell
To increase liposome size:
1. Dried reconstituted vesicle
2. Freeze thawing
3. Induction of vesiculation by PH change
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18. Solvent dispersion method-
1. Ethanol injection
2. Ether injection
3. Water organic phase:
A) Double emulsion method
B) Reverse phase evaporation
C) Stable plurilamellar vesicles.
Detergent solubilization
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30. Evaluation of liposomes
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The liposomes prepared by various techniques are to be evaluated
for their physical properties, has these influence the behavior of
liposomes in vivo.
1. Particle size and particle size distribution-
• Both particle size and particle size distribution of liposomes
influence their physical stability.
• These can be determined by the following method.
a) Laser light scattering
b) Transmission electron microscopy
31. 3/25/2019 31
2.Surface charge
The positive, negative or neutral charge on the surface of the
liposomes is due to the composition of the head groups.
The surface charge of liposomes governs the kinetic and extent of
distribution in vivo, as well as interaction with the target cells.
The method involved in the measurement of surface charge is
based on free-flow electrophoresis of MLVs.
It utilizes a cellulose acetate plate dipped in sodium borate buffer
of pH 8.8.
About 5N moles of lipid samples are applied on tom the plate,
which is then subjected to electrophoresis at 4 ͦ c for 30 mins.
The liposomes get bifurcated depending on their surface charge.
This technique can be used for determining the heterogeneity of
charges in the liposome suspension as well as to detect any
impurities such as fatty acids.
32. 3. Percent drug encapsulated.
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Quantity of drug entrapped in the liposomes helps to estimate the
behavior of the drug in biological system
Liposomes are mixture of encapsulated and unencapsulated drug
fractions
The % of drug encapsulation is done by first separating the free
drug fraction from encapsulated drug fraction
The encapsulated fraction is then made to leak off the liposome
into aqueous solution using suitable detergents
The methods used to separate the free drug from the sample are:
1. Mini column centrifugation method
2. Protamine aggregated method
33. 4. Phase behavior
• At transition temperature liposomes undergo reversible phase
transition
• The transition temperature is the indication of stability permeability
and also indicates the region of drug entrapment Done by DSC.
5. Drug Release Rate
•The rate of drug release from the liposomes can be determined
by in vivo assays which helps to predict the pharmacokinetics
and bioavailability of the drug. However in vivo studies are
found to be more complete.
• Liposome encapsulating the tracer [ᵌH] insulin are employed for
the study.
• This [ᵌH] insulin is preferred, as it is released only in the ECF
and undergoes rapid renal excretion of the face tracer coupled to
the degradation rate constant o the tracer released from the
liposomes
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34. Applications
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Liposomes as drug or protein delivery vehicles.
Liposome in antimicrobial, antifungal(lung therapeutics) and antiviral
(anti HIV) therapy.
In immunology.
Liposomes as artificial blood surrogates.
Liposomes as radiopharmaceutical and radio diagnostic carriers.
Liposomes in cosmetics and dermatology.
35. CONCLUSION
• Liposomes have been used in a broad range of pharmaceutical
applications.
• Liposomes are showing particular promise as intracellular delivery
systems for anti-sense molecules, ribosomes, proteins/peptides,
and DNA.
• Liposomes with enhanced drug delivery to disease locations, by
ability of long circulation residence times, are now achieving
clinical acceptance.
• Also, liposomes promote targeting of particular diseased cells
within the disease site.
• Finally, liposomal drugs exhibit reduced toxicities and retain
enhanced efficacy compared with free complements.
• Only time will tell which of the above applications and
speculations will prove to be successful.
• However, based on the pharmaceutical applications and available
products, we can say that liposomes have definitely established
their position in modern delivery systems.
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36. References
1. Sahoo SK, Labhasetwar V. Nanotech approaches to drug delivery
and imaging. DDT. 2003;8:24.[PubMed]
2. Gabizon A, Goren D, Cohen R, Barenholz Y. Development of
liposomal anthracyclines: from basics to clinical applications. J
Control Release. 1998;53:275–279. doi: 10.1016/S0168-
3659(97)00261-7.[PubMed] [CrossRef]
3. Allen TM. Liposomes. Opportunities in drug
delivery. Drugs. 1997;54(Suppl 4):8–14. [PubMed]
4. Chrai SS, Murari R, Imran A. Liposomes: a review. Bio
Pharm. 2001;14(11):10–14.
5. Andreas W, Karola VU. Liposome technology for industrial
purposes. J Drug Deliv. 2011;2011:9.
6. Atrooz OM. Effects of alkylresorcinolic lipids obtained from
acetonic extract of Jordanian wheat grains on liposome
properties. Int J Biol Chem. 2011;5(5):314–321.
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