Liposomes are spherical vesicles made of phospholipid bilayers that can encapsulate hydrophilic or hydrophobic drugs. They range in size from 25nm to 5000nm. This document discusses the structure of liposomes and their components, including phospholipids and cholesterol. It also covers various preparation methods such as lipid film hydration, extrusion, and detergent removal. Liposomes offer advantages for drug delivery such as the ability to encapsulate different drug types and provide controlled release, but also have challenges like high production costs and drug leakage.

1. Liposomes- A Novel
Drug Delivery System
From – Miss Snehal K. Dhobale
M-Pharm ( Pharmaceutics)

2. What are Liposomes???
• 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.
• Size range: 25nm-5000nm
• Liposomes consist of Cholesterol, Phospholipid
and drug molecule.
2

3. A simple view of liposomes
“Liposomes are microscopic
spheres made from fatty materials,
predominantly phospholipids.
“made up of one or more
concentric lipid bilayers, and range
in size from 50 nanometers to
several micrometers in diameter
3

4. Advantages with liposomes
Suitable for delivery of hydrophobic, hydrophilic
and amphipatic drugs and agents
Liposomes increases efficacy and therapeutic
index of drug (actinomycin-D)
 Liposome increased stability via encapsulation
Suitable for controlled release
Suitable to give localized action in particular
tissues.
Suitable to administer via various routes
Liposomes help reduce the exposure of sensitive
4
tissues to toxic drugs

5. Disadvantages of liposomes
Production cost is high.
Leakage and fusion of encapsulated drug /
molecules.
Sometimes phospholipid undergoes
oxidation and hydrolysis like reaction.
Short half-life.
Low solubility. 5

6. Components of liposomes
The structural components of liposomes
include:
A. Phospholipids
B. cholesterol

7. PHOSPHOLIPID
• Major component of biological cell membrane
Phospholipid
Hydrophobic
tail
2 fatty acid
chain containing
10-20 carbon
atoms
0-6 double bond
in each chain
Hydrophillic
head or polar
head
Phosphoric acid
bound to water
soluble
molecule
7

8. Commonly used other
Phospholipids
Natural phospholipid
 PC- phosphatidyl choline
 PE- phosphatidyl ethanolamine
 PS –phosphatidyl serine
Synthetic phosholipid
 DOPC = Dioleoyl Phosphatidylcholine
 DOPE = Dioleoyl phosphatidyl ethanolamine
 DSPC = Distearoyl phosphatidyl choline
 DSPE = Distearoyl phosphatidyl ethanolamine
 DLPC = Dilauryl phosphatidyl choline
8

9. Phosphatidylcholine PC
• The most common
phospholipid use is
phosphatidylcholine PC
• Phosphatidylcholine is
amphipathic molecule
containing
i. A hydrophillic polar head
group phosphocholine
ii. A glycerol bridge
iii. A pair of hydrophobic
acyl hydrocarbon chain
9

10. Cholesterol:
• Incorporation of sterols in liposome bilayer can bring about
major changes in the preparation of these membranes.
• Cholesterol does not by itself form bilayer structure,but
can be incorporated into phospholipid membranes in very
high concentration unto 1:1 or even 2:1 molar ratios of PC.
• Cholesterol incorporation increases the separation
between the cholin head groups and eliminates the normal
electrostatic and hydrogen-bonding interactions.
10

11. Role of cholesterol in bilayer formation:
 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.
 Incorporated into phospholipid membrane upto
1:1 or 2:1 of cholesterol to PC.
11

12. Preparation of Liposomes
• Mechanism of Vesicle Formation
A. The budding theory
B. The bilayer phospholipids theory
12

13. The budding theory
– Stress induced hydration of phospholipids
– Organization in to lamellar arrays
– Results in to budding of lipid bilayer leading
to down sizing
SUV OLV
13

14. The bilayer phospholipids theory
• Liposomes are formed when thin lipid films are hydrated
• The hydrated lipid sheets detach during agitation and self-close
to form large, multilamellar vesicles (LMV)
14

15. Modes of liposomes/cell interaction
1.
Endocytosis
2. Adsorption
3. fusion 4. Lipid
transfer
15

16. Factors affecting release of drug
• Solvents
• pH
• Temperature
• Agitation
• Enzymes
• Cell culture
• Volume
Drug release from liposomes
• The lipid bilayer of the
liposome can fuse with
other bilayers (e.g. cell
membrane) thus
delivering the liposome
contents.
16

17. CLASSIFICATION OF LIPOSOMES
Structure
Method of
preparation
Composition
and application
Conventional
liposome
Speciality
liposome
17

18. 1. Classification of liposomes based on Structure
Unilamellar (UV)-all size range
Small Unilamellar(SUV) [20-100nm]
Medium Unilamellar (MUV)
Large Unilamellar (LUV) [>100nm]
Giant Unilamellar (GUV) [>1μm]
Multi Lamellar Vesicles (MLV) [0.5nm]
Oligolamellar Vesicles (OLV)
Multi Vesicular (MV) [>1μm] 18

19. 2. Classification of liposomes Based on Method of Preparation
Single or oligo lamellar vesicle made by reverse phase evaporation method (REV’s)
Multi lamellar vesicle made by reverse phase evaporation method (MLV-REV
Stable pluri lamellar vesicle (SPLV)
Frozen and thawed multi lamellar vesicle (FATMLV)
Vesicle prepared by extrusion technique (VET)
Dehydration- Rehydration method (DRV)
Dehydration- Rehydration method (DRV)
19

20. 3. Classification of liposomes Based on Composition and Application
Type of liposome Abbreviation Composition
Conventional liposome CL Neutral of negatively charge phospholipids and cholesterol
Fusogenic liposome RSVE Reconstituted sendai virus enveops
pH sensitive liposomes - Phospholipids such as PER or DOPE
Cationic liposome - Cationic lipid with DOPE
Long circulatory liposome LCL Neutral high temp, cholesterol and 5-10% PEG, DSP
Immune liposome IL CL or LCL with attached monoclonal antibody or recognition
sequences
20

21. 4. Classification of Liposomes Based Upon
Conventional Liposome
1). Stabilize natural lecithin (PC)
mixtures
2). Synthetic identical, chain
phospholipids
3). Glycolipids containing
liposome
21

22. 5.)Classification of Liposomes based upon Speciality
5.)
Liposomes
Bipolar Fatty Acids
Antibody directed Liposome
Methyl/Methylene x- linked liposome
Lipoprotein coated liposome
Carbohydrate coated liposome
Muiltiple Encapsulated Liposome
22

23. Methods of liposome preparation
Passive loading techniques Active loading techniques
Mechanical disp
ersion
methods
Solvent dispersi
on
methods
Detergent
removal
technique
 LIPID FILM HYDRATION
 BY HAND SHAKING,
 FREEZE DRYING
 NON HAND SHAKING
 MICRO
EMULSIFICATION
 SONICATION
 FRENCH PRESSURE
CELL
 MEMBRANE EXTRUSON
 DRIED RECONSTITUTED
VESICLES
 ETHANOL
INJECTION
 ETHER INJECTION
 DOUBLE EMULSION
 REVERSE PHASE
EVAPORATION
1. Detergent removal
from mixed vesicles by
 DIALYSIS
 Column
Chromatography
 DILUTION

24. General Method Of Liposome Preparation
1
• Cholesterol + Lecithin + Charge and Dissolve
in organic solvent
2
• Drying down lipid from organic solvent( Vaccum )
• Dispersion of lipid in aqueous media (Hydration
3
• Purification of resultant Liposomes
• Analysis of final product
24

25. 1. Mechanical dispersion method
Lipid dissolve in organic solvent/co-solvent
Remove organic solvent under vacuum
Film deposition
Solid lipid mixture is hydrated by using aqueous buffer
Lipid spontaneously swell & Hydrate
Liposome
25

26. 1) Lipid Hydration Method
A.) By hand shaking method
vesiculate to
form Multi
lamellar
vesicles(MLVs)
Upon
hydration
lipids swell
and peel out
from RB flask
Then film is
treated with
aqueous
medium
Lipids form
stacks of
film from
organic
solution
26

27. 1) Lipid Hydration Method
B.) NON-HAND SHAKING METHOD
The procedure differs
from hand shaken
method wherein it
uses a stream of
nitrogen to provide
agitation rather than
rotationary
movements.
 Here the lipid film is
exposed to water
saturated nitrogen for
15-20 min
Milky suspension centrifugation
LUV
27

28. 1) Lipid Hydration Method
C.) FREEZE DRYING
• Another method of dispersing the lipid in a finely divided form,
prior to addition of aqueous media, is to freeze dry the lipid
dissolved in a suitable organic solvent.
• The solvent choice depends on the freeze point which needs to
above the temperature of the condenser lyophilizers. Tertiary
butanol is considered to be most ideal solvent.
• After obtaining the dry lipid which is an expanded foam like
structure, water or saline can be added with rapid mixing above
the phase transition temperature to give MLVs.
28

29. 2.) MICRO EMULSIFICATION
• This method is provided
for preparing small lipid
vesicles in commercial
quantities by
microemulsifying lipid
compositions using very
high shear forces
generated in a
homogenizing apparatus
operated at high
pressures at a selected
temperature.
• At least 20 circulations
(approximately 10
minutes) but not greater
than 200 circulations
(100 minutes) are
sufficient to produce a
micro emulsion of small
vesicles suitable for
biological application.
29

30. 3.) SONICATION
a)Probe sonication
 The tip of a sonicator is directly
engrossed into the liposome dispersion.
 The energy input into lipid dispersion is
very high in this method.
 The coupling of energy at the tip results
in local hotness; therefore, the vessel
must be engrossed into a water/ice
bath.
b)Bath sonication
 The liposome dispersion in a cylinder is
placed into a bath sonicator.
 Controlling the temperature of the lipid
dispersion is usually easier in this
method, in contrast to sonication by
dispersal directly using the tip.
30

31. 4.) FRENCH PRESSURE CELL
• The method involves the
extrusion of MLV at 20,000 psi at
4°C through a small orifice.
• The method has several
advantages over sonication
method.
• The method is simple rapid,
reproducible and involves gentle
handling of unstable materials.
• The resulting liposomes are
somewhat larger than sonicated
SUVs.
• The drawbacks of the method
are that the temperature is
difficult to achieve and the
working volumes are relatively
small (about 50 mL maximum).
31

32. 5.) MEMBRANE EXTRUSON
 Liposomes passed through membrane of defined pore size.
Lower pressure is required (<100 psi).
 LUVs as well as MLVs can be processed.
 Vesicle contents are exchanged with dispersion medium during
breaking and resealing of phospholipid bilayers as they pass
through the polycarbonate membrane.
 For high entrapment, the water soluble compounds should be
present in suspending medium during the extrusion process.
32

33. 6.) DRIED RECONSTITUTED VESICLES
SUV’s in SUV’s with
DRV
Freeze dried
aqueous
solute to be
membrane
phase
entrapped
Solutes with
oligo and uni
lamellar
Freeze membranes
drying Rehydration
33

34. B] Solvent dispersion methods
• Ethanol injection –SUV
• Ether injection -LUV
• Reverse phase evaporation vesicle –LUV
• Double emulsion vesicles Stable
plurilamellar vesicles
34

35. 1.) Ethanol Injection Method
• A lipid solution of ethanol is
rapidly injected to a vast
excess of buffer. The MLVs
are immediately formed.
• The drawbacks of the method
are that the population is
heterogeneous (30-110 nm),
liposomes are very dilute, it is
difficult to remove all ethanol
because it forms azeotrope
with water and the possibility
of various biologically active
macromolecules to inactivation
in the presence of even low
amounts of ethanol.
35

36. 2.) Ether Infusion Method
• A solution of lipids dissolved
in diethyl ether or
ether/methanol mixture is
slowly injected to an
aqueous solution of the
material to be encapsulated
at 55-65°C or under reduced
pressure.
• The subsequent removal of
ether under vacuum leads to
the formation of liposomes.
• This method is used to treat
sensitive lipids very gently.
36

37. Double emulsification
• In this process, an active ingredient is first dissolved in an
aqueous phase (w1) which is then emulsified in an organic
solvent of a polymer to make a primary w1/o emulsion.
• This primary emulsion is further mixed in an emulsifier-containing
aqueous solution (w2) to make a w1/o/w2
double emulsion.
• The removal of the solvent leaves microspheres in the
aqueous continuous phase, making it possible to collect
them by filtering or centrifuging.
37

38. 3.) Reverse-phase evaporation
Lipid organic solvent and
aqueous solution are
i. mixed,
ii. sonicated,
iii. formation of w/o
emulsion,
iv. evaporate to remove
the organic solvent
Lipids form a phospholipid
bilayer on vigorous
shaking , water droplets
collapse and formation of
LUV’s takes place. 38

39. Reverse phase evaporation technique.
Lipid in solvent
solution
Two-phase system Water in oil
emulsion
Gel formation Solvent removal
REV liposomes
Conti…
39

40. C. Detergent removal method
• The micellar dispersion is then subjected to
one of the following methods to remove the
detergent:
I. DIALYSIS :- Detergents with high CMC
(10-20 mM ) are used so that their removal
is facilitated e.g. bile salts- sodium cholate
and sodium deoxycholate , or synthetic
detergents like octileglucoside .
II. COLUMN CHROMATOGRAPHY :- By
passing dispersion over a Sephadex G-25
column. 40

41. i.) Dialysis Method
Dialysis is the simplest
procedure used for the removal
of the unbound drug, except
when macromolecular
compounds are involved
Advantages:
Dialysis Technique requiring
no complicated or expensive
equipment.
Dialysis is effective in
removing nearly all of the free
drug with a sufficient number
of changes of the dialyzing
medium 41

42. ii.) Column Chromatography
• Phospholipid in the form of either
sonicated vesicle or as a dry film, at a
molar ratio of 2:1 with deoxycholate form
unilamellar vesicles of 100nm on removal
of deoxycholate by column
chromatography
42

43. B. Active loading technique
AFTER DRYING IN PROCESS
FILM/CAKE OF LIPID IS FROM
STACKS OF LIPID
BILAYER FORM
SWELLING IN FLUID
SHEET IS SELF CLOSE
LOADING OF DRUG
ON pH- GRADIENT TECHNIQUE
FORMATION OF BILAYER
(LIPOSOMES) IF DRUG
 Two steps process generates this pH imbalance
and active (remote) loading.
1) Vesicles are prepared in low pH solution, thus
generating low pH within the liposomal interiors
2) followed by addition of the base to
extraliposomal medium.
 Basic compounds, carrying amino groups are
relatively lipophipic at high pH and hydrophilic at
low pH.
43

44. 1.) Lyophilization
• Freeze-drying (lyophilization) involves the removal of water from
products in the frozen state at extremely low pressures.
• The process is generally used to dry products and are thermo labile
and would be destroyed by heat-drying.
• The technique has a great potential as a method to solve long term
stability problems with respect to liposomal stability.
• It is exposed that leakage of entrapped materials may take place
during the process of freeze- drying and on reconstitution.
44

45. 2.) Pro-liposomes:
lipid Dried
over
lipid
Finely divided
particulate
support like
powdered
NACL/ sorbital
 To increase the surface area of dried lipid film and to facilitate continuous
hydration and lipid is dried over the finally divided particulate support i.e.-
NaCl, Sorbitol, or other polysaccharides. These dried lipid coated
particulates are called as proliposomes
 Proliposomes form dispersion of MLVs on addition of water, where support
is rapidly dissolved and lipid film hydrate to form MLVs
45

46. Uses of liposomes
• Chelation therapy for treatment of heavy metal poisoning
• Enzyme replacement
• Diagnostic imaging of tumors
• Study of membranes
• In gene delivery.
• As drug delivery carriers.
• Enzyme replacement therapy.
• Liposomes in antiviral/anti microbial therapy.
• In multi drug resistance.
• In tumour therapy.
• In immunology.
• In cosmetology
46

47. Applications
• Liposomes are successfully used to entrap anticancer
drugs. This increases circulation life time, protects from
metabolic degradation.
1.Cancer chemotherapy
• Steroids used for arthritis can be incorporated into large
MLVs.
• Alteration in blood glucose levels in diabetic animals was
obtained by oral administration of liposome encapsulated
insulin.
2.Liposomes as carrier of drug
in oral treatment
• Drugs like triamcilone, methotrexate, benzocaine,
corticosteroids etc can be successfully incorporated as
topical liposome
3.Liposomes for topical
applications
4. Liposomes for pulmonary
delivery
Inhalational devices like nebulizers are use to
produce an aerosol of droplets containing
liposomes.
47

48. DNA delivery of Genes by Liposomes
 Cheaper than viruses
 No immune response
 Especially good for in-lung
delivery (cystic fibrosis)
 100-1000 times more
plasmid DNA needed for the
same transfer efficiency as
for viral vector
48

49. Lipofection
49

50. Liposomes could serve as tumor specific vehicles
(even without special targeting)
Liposomes better penetrate into tissues with disrupted endothelial lining
50

51. Characterization of liposomes
• Shape, size and its distribution
• Surface charge
• Percentage drug entrapment
• Entrapped volume
• Lamellarity
• Phase behavior of liposome
• Percentage drug release
51

52. References
1) ‘Controlled and Novel Drug Delivery’, “JAIN N.K.’’, CBS Publisher And
Distributors.Page No.307-321.
2) ‘Targeted and controlled drug delivery, Novel carrier Systems’ , “VYAS S.P.
and KHAR R.K.’’, CBS Publishers Page no.181 -195.
3) A.Chonn,P.R.Cullis,“Recent advances in liposome technologies and their
applications for systemic gene delivery”,Advanced Drug Delivery Reviews
4) Liposomes preparation methods by Mohammad riaz ,Pakistan Journal of
Pharmaceutical Sciences Vol.19(1), January 1996, pp.65-77
5) Liposome- as drug carriers-International Journal of Pharmacy & life sciences-
Himanshu Anwekar*, Sitasharan Patel and A.K Singhai
6) http://www.avantilipids.com
7) http://www. Mssm.edu/medicine/thrombosis/phosphol.html
8) Garrett, R. and Grisham C. Biochemistry, 2nd ed. Saunders Colleges
Publishing. New York (1999). 264
9) "Liposomes." www.collabo.com/liposom0.htm
10) Sharma Vijay K1*, Liposomes: Present Prospective and Future
Challenges,International Journal Of Current Pharmaceutical Review And
Research, oct 2010,vol1, issue 2,6-16
11) Himanshu Anwekar*, Liposome- as drug carriers, International Journal Of
Pharmacy & Life Sciences, Vol.2, Issue 7: July: 2011, 945-951 52

53. 53