Liposomes are spherical vesicles composed of phospholipid bilayers that can encapsulate water-soluble drugs in their aqueous core and lipid-soluble drugs within their membrane. They have advantages for drug delivery such as providing selective targeting to tissues, increasing drug efficacy and stability, and reducing toxicity. However, they also have challenges with drug leakage and uptake by the reticuloendothelial system. Liposomes can be classified based on their lamellarity and size, and are prepared using methods like film hydration, ethanol injection, and detergent removal. They have applications for delivery of drugs, genes, vaccines, and contrast agents for imaging.

1. Targeted Drug Delivery System
LIPOSOMES

2. Learning Objectives
• Introduction
• Mechanism of liposome formation
• Classification of liposomes
• Material used in preparation of liposomes
• Methodes of liposome preparation
• Characterization of liposomes
• Stability
• Therapeutic application
• References

3. What are Liposomes?
• They are simply vesicles or ‘bags’ in which
an aqueous volume is entirely enclosed by
a membrane composed of lipid (fat)
molecules, usually phospholipids.

4. •Structurally, liposomes are
bilayered vesicles in which an
aqueous volume is entirely
enclosed by a membranous lipid
bilayer mainly composed of natural
or synthetic phospholipids.
• These vesicles can encapsulate water-soluble
drugs in their aqueous spaces and lipid soluble drug
within the membrane itself.
• The unique property of liposomes, namely their
versatile, biodegradable, hypoallergenic nature,
along with their similarity to biological membranes
are the important factors in the continued efforts to
develop liposomal drug delivery froms.

5. Advantages of liposome :
• Provides selective passive targeting to tumor
tissues
• Increased efficacy and therapeutic index
• Increased stability via encapsulation
• Reduction in toxicity of the encapsulated agent.
• Improved pharmacokinetic effects
• Used as carriers for controlled and sustained
drug delivery
• Can be made into variety of sizes.

6. Disadvantages of liposome :
• Leakage of encapsulated drug during storage.
• Uptake of liposomes by the reticuloendothelial
system
• Batch to batch variation
• Difficult in large scale manufacturing and
sterilization
• Once administered, liposomes can not be removed
• Possibility of dumping, due to faulty administration

7. 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 imunoliposomes

8. • 1987 first synthetic cationic liposomes deliver
genes to cells
• 1987 first sterically stabilized long circulating
liposomes system introduced
• 1992 first lioposome based non viral vecrtor
gene therapy clinical trail on cystic fibrosis
patients
• 1993 frist liposome based vaccine against
hepatitis A is marketed
• 1995 first long circulating immunoliposomes
• 1995 the liposomes encapsulated from of the
anticancer drug doxorubicin and
daunorubicin approved for human use
• 1997 first liposomes based DNA vaccine

9. Mechanism of liposome formation
• In order to understand why liposomes are formed
when phospholipids are hydrated, it requires a basic
understanding of physiochemical features of
phospholipids.
• Phospholipids are amphipathic molecules (having
affinity for both aqueous and polar moieties) as they
have a hydrophobic tail is composed of two fatty
acids containing 10-24 carbon atoms and 0-6
double bonds in each chain.

10. • In aqueous medium the phospholipid molecules
are oriented in such a way that the polar portion of
the molecule remains in contact with the polar
environment and at the same shields the non-polar
part.
• They align themselves closely in planer bilayer
sheets to minimize the interaction between the
bulky aqueous phase and long hydrocarbon fatty
acyl chains.
• This alignment requires input of sufficient amount
of energy (in the form of shaking, sonication,
homogenization, heating, etc).

11. • Interactions are completely eliminated when
these sheets fold over themselves to form
closed, sealed and continuous bilayer vesicles.

12. Classification of liposomes
1. Multilamellar vesicles (MLVs) : consist of several
bilayers and having size ranging from 100nm-20m
2. Small unilamellar vesicles (SUVs) : composed of
single lipid bilayer with dimeter ranging from 20-
100nm
3. Large unilamellar vesicles (LUVs) : consist of
single bilayer with diameter ranging from 0.1-1m
4. Multivesicular vesicles (MVVs) : consist of
vesicles with size ranging from 100nm-20m

14. Materials used in preparation of liposomes
A.Phospholipids :
• It 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.
• It is originated from animal (hen egg) and
vegetable (soyabean).

16. B. Steroids :
• Cholesterol is generally used steroid in the
formulation of liposomes.
• It improves the fluidity of the bilayer
membrane and reduces the permeability of
bilayer membrane in the presence of
biological fluids such as blood / plasma.
• Cholesterol appers to reduce the
interactions with blood proteins.

17. Methods of liposomes
preparations
Passive loading Active loading
technique technique
Mechanical dispersion Detergent removal Solvent dispersion
methods methods methods

18. • Mechanical dispersion methods
Lipid is solublised in organic solvent, drug to be
entrapped is solubilise in aqueous solvent, the
lipid phase is hydrated at high speed stirring due
to affinity of aqueous phase to polar head it is
entrapped in lipid vesicles.
e.g. Lipid film hydration, Micro-emulsification
( Microfluidizer ), Sonication, Dried reconstituted
vesicle

19. • Solvent dispersion methods
in this method, lipids are first dissolved in organic
solvent, which then brought in to contact with
aqueous phase containing material which is to
be entrapped in liposome under rapid dilution
and rapid evaporation of organic solvent.
e.g.
Ethanol injection
Ether injection
De-emulsification
• Detergent removal methods

20. Physical Characterization
Parameter Characterization method
Vesicle shape and surface Transmission electron microscopy,
morphology Freeze-fracture electron microscopy
Mean vesicle size and size Dynamic light scattering, zetasizer,
distribution Photon correlation spectroscopy, laser
light scattering, gel permeation and gel
exclusion
Surface charge Free-flow electrophoresis
Electrical surface potential Zetapotential measurements & pH sensitive
and surface pH probes
Percent of free drug/ Minicolumn centrifugation, ion-exchange
percent capture chromatography, radiolabelling
Drug release Diffusion cell/ dialysis

21. Chemical Characterization
Parameter Characterization method
Phospholipid concentration Barlett assay, stewart assay, HPLC
Cholesterol concentration Cholesterol oxidase assay and HPLC
Phopholipid peroxidation UV absorbance, Iodometric and GLC
Phospholipid hydrolysis,
HPLC and TLC
Cholesterol auto-oxidation
Osmolarity Osmometer

22. Biological Characterization
Parameter Characterization method
Sterility Aerobic or anaerobic cultures
Pyrogenicity Limulus Amebocyte Lysate (LAL) test
Animal toxicity Monitoring survival rates, histology and
pathology

23. Stability
• Physical stability :
Once liposomes are formed, they behave similar to
the other colloidal particles suspended in water.
Neutral particles tend to aggregate or flocculate and
sediment with increase in size on storage. Adding
charged lipids such as stearyl amine, diactyl
phosphate and phosphatidyl serine can control the
aggregation.
The addition of charged lipids causes repulsion and
prevents major changes in the overall size of
liposomes.

24. • Chemical stability :
Phospholipids, especially those derived from
natural sources, are subject to two major
degradative reaction :
A. Lipid peroxidation : most phospolipid liposomes
contain unsaturated acyl chains as part of their
molecular structure and susceptible to oxidative
degradation. It can be minimized by the use of
animal derived lipids like egg PC, which has less
saturated lipids, use of light resistant containers,
use of antioxidants are useful in minimizing
oxidation.

25. B. Lipid hydrolysis :
hydrolysis in phospolipids results in the formation of
free fatty acids and lyso-lecithin. Selecting a good
source of lipid, temperature, pH, and minimizing
oxidation.
• Biological stability :
liposomes release entrapped molecules rapidly
when incubated with blood or plasma. This
instability is attributed to the transfer of bilayer lipids
to albumin and high density liposomes.

26. Therapeutic applications of liposomes
1. Liposomes as drug / protein delivery vehicles
• Controlled and sustain release in situ
• Enhanced drug solubilization
• Enzyme replacement therapy and lysosomal
storage disorders
• Altered pharmacokinetics and biodistribution
2. Liposomes in antimicrobial, antifungal and
antiviral therapy
3. Liposomes in tumour therapy
• Carrier of small cytotoxic molecules
• Vehicle for macromolecules as cytokines and
genes

27. 4. Liposomes in gene delivery
• Genes and antisense therapy
• Genetic (DNA) vaccination
5. Liposomes in immunology
6. Liposomes as radiopharmaceutical and radio
diagnostic carrier
7. Liposomes in cosmetic and dermatology
8. Liposomes in enzyme immobilization and
bioractor technology

28. Drug Route of Targeted
administration Diseases
Amphotericin-B Oral delivery Mycotic infection
Insulin Oral, Ocular, Diabetic mellitus
Pulmonary and
Transdermal delivery
Ketoprofen Ocular delivery Pain muscle condition
Pentoxyfylline Pulmonary delivery Asthma
Tobramycin Pulmonary delivery Pseudomonas
infection, aeruginosa

29. Drug Route of Targeted
administration Diseases
Salbutamol Pulmonary delivery Asthma
Benzocain Transdermal ulcer on mucous surface
with pain
Ibuprofen Oral delivery Rheumatoid arthritis
Adrenaline Ocular delivery Glucoma, Conjectivitis
Penicillin G Pulmonary delivery Meningococal,
staphylococcal
Methotrexate Transdermal Cancer

30. Marketed Drug used Target Company
product diseases
DoxilTM or Doxorubicin Kaposi’s SEQUUS, USA
CaelyxTM sarcoma
DaunoXomeTM Daunorubicin Kaposi’s NeXstar, USA
sarcoma, breast
& lung cancer
AmphotecTM Amphotericin-B fungal infections, SEQUUS, USA
Leishmaniasis
VENTUSTM Prostaglandin-E1 Systemic The liposome
inflammatory company, USA
diseases
ALECTM Dry protein free Expanding lung Britannia Pharm,
powder of DPPC- diseases in UK
PG babies

31. Marketed Drug used Target Company
product diseases
Topex-Br Terbutaline Asthma Ozone, USA
sulphate
Depocyt Cytarabine Cancer therapy Skye Pharm,
USA
Novasome® Smallpox vaccine Smallpox Novavax, USA
Avian retrovirus Killed avian Chicken pox Vineland lab,
vaccine retrovirus USA
Epaxal –Berna Inactivated Hepatitis A Swiss serum &
Vaccine hepatitis-A vaccine institute,
Virions Switzerland

32. Conclusion
• Liposomes are one of the unique drug delivery
system, which can be of potential use in controlling
and targeting drug delivery.
• Liposomes are administrated orally, parenterally
and topically as well as used in cosmetic and hair
technologies, sustained release formulations,
diagnostic purpose and as good carriers in gene
delivery.
• Nowadays liposomes are used as versatile carriers
for targeted delivery of drug.

33. Reference
• Targeted and controlled drug delivery, S.P.Vyas
and R.K.Khar, CBS Publication 2008,
Nanoparticles – page no 331 to 386.
Resealed Erythrocytes – page no 387 to 416.
Liposomes – page no 173 to 248.
• Text book of Industrial Pharmacy, Shobha Rani
Hiremath, Orient Longman Private ltd.
Nanoparticles – 129 to 142.
Liposomes – 97 to 110

34. • Medical applications of nanotechnology by
Timothy E. Morey, University of Florida.
• Liposome: A versatile platform for targeted
delivery of drugs by Sanjay S. Patel
• Resealed Erythrocytes : A Review by
A.V.Gothoskar MIT Campus, Pune.
• www.pharmainfo.net
• www.google.com

35. Any
question...

36. Thank You