NAME: V.SPANDANA

REGISTRATION NUMBER: 133H1S1103

BRANCH: PHARMACEUTICAL TECHNOLOGY

COLLEGE: SRI SAI ADITYA INSTITUTE OF PHARMACEUTICAL

SCIENCES & RESEARCH

INTRODUCTION

MECHANISM OF LIPOSOME FORMATION

TYPES OF PHOSPHOLIPIDS

CLASSIFICATION

BIOLOGICAL FATE OF LIPOSOMES

ADVANTAGES & DISADVANTAGES

METHODS OF PREPARATION

CHARACTERIZATION OF LIPOSOMES

STABILITY OF LIPOSOMES

LIPOSOMAL PHARMACOKINETICS

APPLICATIONS

Liposomes were discovered by Bhangam and co-workers in

1960’s.

Liposomes are simple microscopic , concentric bi-layered vesicles

in which an aqueous volume is entirely enclosed by a

membranous lipid bi-layer mainly composed of phospholipids

and cholesterol.

The exact location of the drug in the liposome depends up on the

physicochemical characterization of the drug and the composition

of the lipid content.

Stable liposomes from phospholipids are formed only as

temperature above the “gel to liquid crystalline” phase transition

temperature (Tc)

Vesicles are formed by hydrophobic effect.

Ratio of hydrophilic and hydrophobic moieties.

Critical packing parameter (CPP)

If CPP value is less than 0.5 then liposomes are formed by

hydrophobic effect.

If CPP value is more than 0.5 then liposomes are formed by

hydrophilic effect.

If CPP value is between 0.5 – 1 then liposomes are formed by

surfactant effect.

CPP = v / lc Ap = Ahp / Ap

Where:

v = hydrophobic group volume

lc = hydrophobic group length

AP = cross sectional area of hydrophilic head group

Ahp = cross sectional area of hydrophobic head group

The phospholipids used in liposomes are

Phosphotidyl choline

Phosphotidyl ethanolamine

Phosphotidyl serine

Phosphotidyl glycerol

Cholesterol alone cannot form liposome but with lipids it

intercalates i.e., Hydroxyl group aligns towards water surface and

aliphatic chain parallel to acyl chains in the center of bi-layer.

Widely used polar phospholipids is phosphotidyl choline which is

used alone and in combination with cholesterol.

Cholesterol condenses the packing of phospholipids in bi-layer

above the phase transition temperature

BASED ON STRUCTURE :

Multi-lamellar large vesicles (>0.5 µm) MLV

Oligo-lamellar vesicles (0.1 – 1µm) OLV

Uni-lamellar vesicles ( All size ranges) UV

Small uni-lamellar vesicles (20 – 100 nm) SUV

Medium size uni-lamellar vesicles (>100 nm) MUV

Large uni-lamellar vesicles (>100 nm) LUV

Giant uni-lamellar vesicles (>1 µm) GUV

Multi-vesicular vesicles (>1 µm) MV

BAESD ON LIPOSOMAL FORMATION:

Reverse phase evaporation REV

Multi-lamellar vesicle by REV MLV-REV

Stable plurilamellar vesicle SPLV

Frozen and thawed MLV FATLV

Vesicles prepared by extrusion techniques VET

Dried reconstituted vesicles DRV

Liposomes in blood stream taken up by reticulo- endothelial

system.

The macrophages engulf the liposomes which are taken by the

reticulo-endothelial system (endocytosis).

Then phagosome and lysosome combine and form as a

phagolysosome.

The membrane of phagolysosome have proton pumps which

decrease the pH of phagolysosome and the enzyme phospholipase

destruct the liposomal membrane and releases the drug from

destructed liposome.

ADVANTAGES:

Biocompatibility and Biodegradability.

Easy manufacture.

Targeted drug delivery

Prolonged circulation in stealth mode

Able to protect encapsulated drug from degradation.

DISADVANTAGES:

Poor stability

High manufacturing cost

Poor loading capacity

Challenging sterilization

Poor reproducibility

Liposomes are prepared by two methods. They are:-

Passive Loading Technique

Active Loading Technique

PASSIVE LOADING TECHNIQUE:

The passive loading technique again subdivided into 3methods.

Mechanical Dispersion Method

Lipid Film Hydration

• Hand Shaking

• Non Hand Shaking

• Freeze Drying

Microemulsion

Sonication

French Pressure cell

Membrane Extrusion

Dried reconstituted Vesicles

Freeze Thawed Liposomes

SOLVENT DISPERSION METHODS

Ethanol injection

Ether injection

Double Emulsion Vesicles

Reverse Phase Evaporation

Stable Plurilamellar Vesicles

DETERGENT REMOVAL METHODS

Detergent ( cholate,alkyl glycoside) removal from micelles by

dialysis

Column Chromatography

Dilution

Visual appearance

Vesicle shape and lamellarity (No.of bi-layers):

• Sample + 31p NMR + Manganese ( affect signal intensity)

• If intensity is decreased by 50% it forms unilamellar vesicles.

• If intensity is decreased by more intensity Multilamellar vesicles

are formed.

• Freeze fracture electron microscopy

• Optical microscopy

Vesicle size

• Light microscopy

• Fluorescent microscopy

• Electron microscopy :SEM,TEM

• Laser light scattering

• Gel permeation

• Ultracentrifugation

• Optical microscopy

Liposome stability : Determined by physical , biological and

chemical methods.

Surface charge : Determined by Electrophoresis(Zeta potential)

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

Chemical characterization

• Quantitative determination of phospholipids

• Phospholipid hydrolysis

• Phospholipid oxidation

• Cholesterol analysis

Phospholipid determination: (Bartlett assay)

• Phospholipid phosphorus + Hydrolysis = Inorganic phosphate

• Inorganic phosphate + ammonium molybdate = Phosphomolybdic

acid

• Phosphomolybdic acid + Amino naphthyl sulfonic acid = reduced

to blue color whose intensity is measured and compared with

standard

Phospholipid Hydrolysis:

• Phospholipids + Hydrolysis = Lysolecithin

• One chain is lost by deesterification

• Determined by HPLC

Phospholipid oxidation:

• Free radical determination by UV, Iodometric method, GLC etc.

Cholesterol analysis:

• Cholesterol + Iron + Reagent ( Ferric perchlorate, ethyl acetate

sulfuric acid = purple complex , which is determined at 610 nm).

Liposomes stability can be done in two ways.

• In vitro stability

• In vivo stability

IN VITRO STABILITY:

Liposomes are not thermodynamically stable but they represents a

metastable state.

Liposomal vesicles possess excess energy.

Phospholipids are prone to oxidation and hydrolysis leads to their

degradation.

The method of preparation, nature of amphipile and the

encapsulated drug effects membrane fluidity/rigidity and

permeability characteristics.

Drug leakage from aqueous domains of lipid bilayers i.e.,

Hydrophilic drugs.

Physicochemical and bio environmental stimuli.

IN VIVO STABILITY:

Rapid RES uptake fast biodegradation.

Gastric stability for orally administered liposomes

LIPOSOMAL PHAMACOKINETICS:

Protection of drug from metabolism and inactivation in plasma.

Decreased volume of distribution and hence decrease in non

specific localization of drug.

High therapeutic index.

Decreased amount and type of non specific toxicity.

Increase in concentration of drug at target site.

Formulation of antineoplastic drugs into liposomes will

significantly enhances systemic circulation time.

Decreased toxicity by reducing free drug levels in plasma.

Increased EPR (Enhanced permeability &retention effect).

Decreased cardio-toxicity of Doxorubicin by liposomal

encapsulation.

Positively charged liposomes have enhanced immunogenic

properties for vaccines and hypersensitivity responses.

PEGylated liposomes are recent advancement in brain targeted

drug delivery systems.

Liposomes used as drug carriers for efficient treatment of neuronal

inflammation (Methyl prednisolone) & others exhibited superior

anti inflammatory activity than

BRAND NAME DRUG CATEGORY ROUTE

Doxil Doxorubicin Anticancer Intravenous

Daunoxome Daunorubicin Anticancer Intravenous

Epaxel Hepatitis A

vaccine

Protection against

Hepatitis

Subcutaneous

Elamax Lidocaine Local anesthetic Topical

Mikasome Amikacine Antibacterial Intravenous

DRUGS CATEGORY ROUTE OF

ADMINISTRATION

Oleonolic acid Anticancer Oral

Midazolam Sedative Oral

Diclofenac sodium Arthritis Topical

Cytarabine Anticancer Parentral

Insulin Diabetes Mellitus Pulmonary

Acyclovir Genital Herpes Vaginal

Liposomes are extremely useful drug carrier systems , additives

and tools in various scientific domains.

Specially for drug delivery and targeting in pharmaceutical fields.

The use of liposomes in delivery of drugs and genes to tumour

sites are more promising and may serve as a major area for focus

of future research.

www.slideshare.com

www.authorstream.com

Targetted & controlled Drug delivery Novel carrier systems

- S.P.Vyas

- R.K.Khar

Novel drug delivery systems by N.K.Jain