liposomes

3. What are liposomes
• Liposome is Greek word - lipo means “ fat ”
- soma means “ body ”
• These are the micro-particulate drug carriers
consisting of one or more concentric spheres of lipid
bilayer separated by aqueous buffer compartments.
• When phospholipids are dispersed in water they
spontaneously form closed structures with internal
aqueous compartments bounded by phospholipid
bilayer membranes.
• Their diameter ranges from 80nm to 100um

4. General structure of liposome
.
Lipid bilayer

5.  Phospholipids are amphipathic molecule i.e. having
affinity for both aqueous & polar moieties, as they have a
hydrophobic tail & hydrophilic head.
 The tail portion consist of 2 fatty acid chains having 10-
24 carbon atoms & 0-6 double bonds in each chain.
 The head or polar portion consist of phosphoric acid
bound to a water soluble molecule.
BASIC COMPONENTS OF LIPOSOMES
There are no of structural & non structural components of
liposomes, in which Phospholipids& cholestrol are major ones
PHOSHOLIPIDS

6.  Cholesterol by itself do not form a bilayer structure,
it acts as fluidity buffer.
 That means below phase transition temperature it
makes the membrane less ordered & slightly more
permeable while above phase transition temperature
it makes the membrane more ordered & stable.
 It inserts into membrane with hydroxyl group
oriented towards aqueous surface & aliphatic chain
aligned parallel to acyl chains in the centre of bilayer

11. PHYSICAL DISPERSON METHODE
Hand shaken multi lamellar vesicles(MLV’s)

15. MICRO EMULSIFICATION OF LIPOSOMES

16. MEMBRANE EXTRUSION LIPOSOMES

19. Dried reconstituted vesicle& freeze thawing methode

24. DOUBLE EMULSION VESICLES
 In this phase the outer portion of liposome membrane is
created at a Second interphase between emulsification of an
organic solution in water
w/o emulsion
excess aqous medium
w/o/w emulsion
removal of solvent
unilamellar vesicles

25. Phospholipids brought in to intimate contact with
aqous phase
By addition optimized concentration of detergent
Formation of micellae(liposomes)
Below CMC,detergent molecules exist in free solution,As the
concentration is increased micellae are forrmed
Note: liposome size &shape depends on chemical nature of
detergents, concentration&other lipids invoved

26. Vesicle shape& lamellarity ( No. of bilayers )
 Sample + 31p NMR + Mangnese (affect signal
intensity)
 If intensity is decrease by 50% = unilamellar vesicle
are formed
 If intensity is decrease by more intensity = MLVs are
formed
Freeze fracture electron microscopy.
Vesicles size determined by
 Ultracentrifugation 40
 Gel permeation
Laser light scattering
Electron microscopy: SEM, TEM
Fluorescent microscopy
Light microscopy
Characterization of Liposome: Physical

27. Surface charge: Determined by Electrophoresis
Drug release: Dissolution
Entrapped volume: (water content is determined)
• Water is replaced with deuterium oxide& is analyzed by NMR
Encapsulation efficiency:
•Protamine aggregation method:
•Liposome + Protamine = Precipitation
• Centrifuge (2000 rpm), remove supernatant
•Liposome pellet + Trixon x-100 (surface breaker)
•The encapsulation efficiency can be determined (Analytically)
• Mini column centrifugation

30. APPLICATIONS OF LIPOSOMES
LIPOSOMES IN RESPIRATORY DRUG DELIVERY SYSTEM:
ISONIAZID & RIFAMPICIN
- improved the effect of drugs for tuberculosis.
CYCLOSPORINS
- preferentially absorbed by lungs & show sustained release
LIPOSOMES AS VACCINE ADJUVANTS:
RABIES GLYCOPROTEINS
- interleukin 2 enhancement
CHOLERA TOXIN
- enhanced antibody level

31. LIPOSOMES FOR BRAIN TARGETING
- Addition of sulphatide group to liposome composition
increases their ability to cross blood-brain barrier.
- Liposomes coated with mannose was found to reach brain
tissue easily.
LIPOSOMES AS ANTI-INFECTIVE AGENTS
Active targeting approach
- pentamidin and anamycin for leishmaniasis
Passive targeting approach
- gentamycin for staphylococcal pneumoniasis

32. LIPOSOMES IN TUMOUR THERAPY
DOXARUBICIN
- For the treatment of refractory tumour and breast cancer.
VINCRISTINE
- for the treatment of solid tumour.
LIPOSOMES IN TOPICAL DRUG DELIVERY
TRIAMCINALONE,CORTICOSTEROID,METHOTREXATE etc
Canbe succesfully incorperated as topical liposomes
LIPOSOMES AS DRUG TARGETING

33. 1)Advances In Liposomal Therapeutics by S P Vyas and V Dixit
REFERNCES