liposomes are novel drug delivery dosage systems, where the drug is entrapped in phospholipid bilayered vesicles. the release of drug from the vesicles can be controlled or sustained.
the follwing presentation contain structure, classification and preparation methods, characterization and applications of liposomes.
Liposomes, Structure of liposome, phospholipids, classification of liposomes, method of preparation of liposomes, mechanism of liposome formation, application of liposomes.
Liposomes, Structure of liposome, phospholipids, classification of liposomes, method of preparation of liposomes, mechanism of liposome formation, application of 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.
Liposomes are spherical microscopic vesicles consisting phospholipids bilayers which enclose aqueous compartments.
The size of a liposome ranges from some 20 nm up to several micrometers.
Liposomes were first produced in England in 1961 by Alec D. Bangham, who was studying phospholipids and blood clotting.
Small unilamellar vesicles (SUV), 25 to 100 nm in size that consist of a single bilayer
Large unilamellar vesicle (LUV), 100 to 500 nm in size that consist of a single bilayer
Multilamellar vesicle (MLV), 200 nm to several microns, that consist of two or more concentric bilayer
Liposomes-Classification, methods of preparation and application Vijay Hemmadi
liposome preparation and application
A liposome is a tiny bubble (vesicle), made out of the same material as a cell membrane. Liposomes can be filled with drugs, and used to deliver drugs for cancer and other diseases. Membranes are usually made of phospholipids, which are molecules that have a head group and a tail group
NIOSOMES , GENERAL CHARACTERISTICS OF NIOSOME , TYPES OF NIOSOMES , OTHERS TYPES OF NIOSOMES , NIOSOMES VS LIPOSOMES , COMPONENTS OF NIOSOMES , Non-ionic surfactant , Cholesterol , Charge inducing molecule , METHOD OF PREPARATION , preparation of small unilamellar vesicles , Sonication , Micro fluidization , preparation of large unilamellar vesicles , Reverse Phase Evaporation , Ether Injection , preparation of Multilamellar vesicles , Hand shaking method , Trans membrane pH gradient drug uptake process (remote loading) , Miscellaneous method :Multiple membrane extrusion method , The “Bubble” Method , Formation of Niosomes From Proniosomes , SEPARATION OF UNENTRAPPED DRUGS , Gel Filtration , Dialysis , Centrifugation , FACTORS AFFECTING THE PHYSICOCHEMICAL PROPERTIES OF NIOSOMES , Membrane Additives , Temperature of Hydration , PROPERTIES OF DRUGS , AMOUNT AND TYPE OF SURFACTANT
Structure of Surfactants , Resistance to Osmotic Stress , Characterization of niosomes ,Therapeutic applications of Niosomes , For Controlled Release of Drugs , To Improve the Stability and Physical Properties of the Drugs , For Targeting and Retention of Drug in Blood Circulation , Proniosomes , Aspasomes , Vesicles in Water and Oil System (v/w/o) ,Bola - niosomes , Discomes , Deformable niosomes or elastic niosomes , According to the nature of lamellarity ,Small Unilamellar vesicles (SUV) 25 – 500 nm in size.,Large Unilamellar vesicles (LUV) 0.1 – 1μm in size , Multilamellar vesicles (MLV) 1-5 μm in size , According to the size:Small Niosomes (100 nm – 200 nm) , Large Niosomes (800 nm – 900 nm),Big Niosomes (2 μm – 4 μm)
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.
Liposomes are spherical microscopic vesicles consisting phospholipids bilayers which enclose aqueous compartments.
The size of a liposome ranges from some 20 nm up to several micrometers.
Liposomes were first produced in England in 1961 by Alec D. Bangham, who was studying phospholipids and blood clotting.
Small unilamellar vesicles (SUV), 25 to 100 nm in size that consist of a single bilayer
Large unilamellar vesicle (LUV), 100 to 500 nm in size that consist of a single bilayer
Multilamellar vesicle (MLV), 200 nm to several microns, that consist of two or more concentric bilayer
Liposomes-Classification, methods of preparation and application Vijay Hemmadi
liposome preparation and application
A liposome is a tiny bubble (vesicle), made out of the same material as a cell membrane. Liposomes can be filled with drugs, and used to deliver drugs for cancer and other diseases. Membranes are usually made of phospholipids, which are molecules that have a head group and a tail group
NIOSOMES , GENERAL CHARACTERISTICS OF NIOSOME , TYPES OF NIOSOMES , OTHERS TYPES OF NIOSOMES , NIOSOMES VS LIPOSOMES , COMPONENTS OF NIOSOMES , Non-ionic surfactant , Cholesterol , Charge inducing molecule , METHOD OF PREPARATION , preparation of small unilamellar vesicles , Sonication , Micro fluidization , preparation of large unilamellar vesicles , Reverse Phase Evaporation , Ether Injection , preparation of Multilamellar vesicles , Hand shaking method , Trans membrane pH gradient drug uptake process (remote loading) , Miscellaneous method :Multiple membrane extrusion method , The “Bubble” Method , Formation of Niosomes From Proniosomes , SEPARATION OF UNENTRAPPED DRUGS , Gel Filtration , Dialysis , Centrifugation , FACTORS AFFECTING THE PHYSICOCHEMICAL PROPERTIES OF NIOSOMES , Membrane Additives , Temperature of Hydration , PROPERTIES OF DRUGS , AMOUNT AND TYPE OF SURFACTANT
Structure of Surfactants , Resistance to Osmotic Stress , Characterization of niosomes ,Therapeutic applications of Niosomes , For Controlled Release of Drugs , To Improve the Stability and Physical Properties of the Drugs , For Targeting and Retention of Drug in Blood Circulation , Proniosomes , Aspasomes , Vesicles in Water and Oil System (v/w/o) ,Bola - niosomes , Discomes , Deformable niosomes or elastic niosomes , According to the nature of lamellarity ,Small Unilamellar vesicles (SUV) 25 – 500 nm in size.,Large Unilamellar vesicles (LUV) 0.1 – 1μm in size , Multilamellar vesicles (MLV) 1-5 μm in size , According to the size:Small Niosomes (100 nm – 200 nm) , Large Niosomes (800 nm – 900 nm),Big Niosomes (2 μm – 4 μm)
Vesicles are colloidal particles in which a concentric bilayer made-up of amphiphilic molecules surrounds an aqueous compartment Useful vehicle for drug delivery of both hydrophobic drugs and hydrophilic drugs, which are encapsulated in the interior aqueous compartment.
liposomes used in preparation of both hydrophilic and hudrophobic drug.
it increases therapeutic efficiency by site targeting and increase circulatory time.
Selection of an animal model is one of the most important steps in any of the experimental pharmacological study.
Animal model preferred for the study must be producing similar disease profile as in the human.
Screening models for evaluation of anti ulcer activitySIVASWAROOP YARASI
A sore that develops on the lining of the oesophagus, stomach or small intestine.
Ulcers occur when stomach acid damages the lining of the digestive tract. Common causes include the bacteria H. Pylori and anti-inflammatory pain relievers including aspirin.
Upper abdominal pain is a common symptom.
Treatment usually includes medication to decrease stomach acid production. If it is caused by bacteria, antibiotics may be required.
Irritable bowel syndrome - diagnosis, pathophysiology and pharmacologySIVASWAROOP YARASI
irritable bowel syndrome (IBS) is a common disorder that affects the large intestine. Signs and symptoms include cramping, abdominal pain, bloating, gas, and diarrhoea or constipation, or both. IBS is a chronic condition that you'll need to manage long term.
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Cancer immunotherapy is a therapy used to treat cancer patients that involves or uses components of the immune system. Some cancer immunotherapies consist of antibodies that bind to, and inhibit the function of, proteins expressed by cancer cells. Other cancer immunotherapies include vaccines and T cell infusions.
Separation techniques are those techniques that can be used to separate two different states of matter such as liquids and solids.
Separation is an important asset to purify component of interest from a mixture.
Adulteration is a practice of substituting original crude drug partially or whole with other similar looking substances but the latter is either free from or inferior in chemical and therapeutic properties. Adulteration in simple words is the debasement of an article. OR Adulteration is broadly defined as admixture or substitution of original or genuine article/ drug with inferior, defective or otherwise useless or harmful substances.
ADULTRANT : The adulterant must be some material which in both cheap and available in fairly large amounts.
The growth and development of plants is regulated by a number of
chemical substances which together exert a complex interaction to
meet the needs of the plant. Five groups of plant hormones are well
established; they are the auxins, gibberellins, cytokinins, abscisic acid
and its derivatives, and ethylene. These substances are of wide distribution
and may, in fact, occur in all higher plants. They are specific
in their action, are active in very low concentrations, and regulate cell
enlargement, cell division, cell differentiation, organogenesis, senescence
and dormancy. Their action is probably sequential. Other hormones
concerned with flower formation and reproduction, but as yet
uncharacterized, have also been envisaged. The essential role of these
substances is illustrated by cell and tissue cultures; without the addition
of suitable hormones no development or cell division occurs. The effects of these very active substances on the production of
secondary metabolites, particularly with a view to producing plants
containing an enhanced proportion of active constituent, are of interest
to pharmacognosists. In such studies the manner in which the results
are recorded is all-important, particularly as the treatment may also
influence the size of the test plant compared with the controls. For
commercial purposes yield per hectare is an obvious criterion, whereas
for biosynthetic studies yield per plant or per cent fresh weight may be
of more significance. For final drug evaluation per cent dry weight is
the most likely requirement.
Oral controlled drug delivery systems - Various Approaches SIVASWAROOP YARASI
these are the drug delivery systems which are given orally and the drug release is such that it releases at a controlled way at a predetermined rate for a particular period of time.
this is an act that comes under Indian judiciary. it deals about the cultivation, supply and proper usage of narcotic substances. it has its own committee that regulates the activities according to the act.
the following document contains various diagnostic test for screening liver function. and interpretation of results, which may confirm the presence of a disease or disorder
Autacoids - pharmacological actions and drugs related to them. SIVASWAROOP YARASI
Autacoids or "autocoids" are biological factors which act like local hormones, have a brief duration, and act near the site of synthesis. The word autacoids comes from the Greek "autos" (self) and "acos" (relief, i.e. drug).
it is a method of miscellaneous instrumental analytical technique. it is one of the thermal analytical techniques used. it also has wide applications in the field of pharmacy.
It is instrumental analytical technique. it is one of the major type of chromatography technique. its basic principle is adsorption. it has many applications in various fields
We all have good and bad thoughts from time to time and situation to situation. We are bombarded daily with spiraling thoughts(both negative and positive) creating all-consuming feel , making us difficult to manage with associated suffering. Good thoughts are like our Mob Signal (Positive thought) amidst noise(negative thought) in the atmosphere. Negative thoughts like noise outweigh positive thoughts. These thoughts often create unwanted confusion, trouble, stress and frustration in our mind as well as chaos in our physical world. Negative thoughts are also known as “distorted thinking”.
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The French Revolution, which began in 1789, was a period of radical social and political upheaval in France. It marked the decline of absolute monarchies, the rise of secular and democratic republics, and the eventual rise of Napoleon Bonaparte. This revolutionary period is crucial in understanding the transition from feudalism to modernity in Europe.
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Operation “Blue Star” is the only event in the history of Independent India where the state went into war with its own people. Even after about 40 years it is not clear if it was culmination of states anger over people of the region, a political game of power or start of dictatorial chapter in the democratic setup.
The people of Punjab felt alienated from main stream due to denial of their just demands during a long democratic struggle since independence. As it happen all over the word, it led to militant struggle with great loss of lives of military, police and civilian personnel. Killing of Indira Gandhi and massacre of innocent Sikhs in Delhi and other India cities was also associated with this movement.
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Synthetic fiber production is a fascinating and complex field that blends chemistry, engineering, and environmental science. By understanding these aspects, students can gain a comprehensive view of synthetic fiber production, its impact on society and the environment, and the potential for future innovations. Synthetic fibers play a crucial role in modern society, impacting various aspects of daily life, industry, and the environment. ynthetic fibers are integral to modern life, offering a range of benefits from cost-effectiveness and versatility to innovative applications and performance characteristics. While they pose environmental challenges, ongoing research and development aim to create more sustainable and eco-friendly alternatives. Understanding the importance of synthetic fibers helps in appreciating their role in the economy, industry, and daily life, while also emphasizing the need for sustainable practices and innovation.
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2. DEFINITION:
• Liposomes are concentric bilayer vesicles in which an aqueous volume is entirely
enclosed by a membranous lipid bilayer mainly composed of natural or
synthetic phospholipids.
• Liposomes were first produced in England in 1961 by Alec D. Bangham.
• The size of a liposome ranges from some 20 nm up to several micrometres.
3. ADVANTAGES:
• Provides selective passive targeting to tumor tissues (Liposomal doxorubicin).
• Increased efficacy and therapeutic index.
• Increased stability via encapsulation.
• Reduction in toxicity of the encapsulated agents.
• Site avoidance effect.
• Improved pharmacokinetic effects (reduced elimination, increased circulation life
times).
• Flexibility to couple with site specific ligands to achieve active targeting.
• Biocompatible and completely biodegradable
4. DISADVANTAGES:
• Production cost higher.
• Leakage and fusion of encapsulated drug.
• Short half life.
• Sometimes phospholipid undergoes oxidation and hydrolysis like reaction.
• Low solubility.
5. STRUCTURE AND COMPONENTS OF LIPOSOME:
• The lipid molecules are usually phospholipids-amphipathic moieties with a
hydrophilic head group and two hydrophobic tails.
• Composition of liposomes:
• The basic components of liposomes are phospholipids which are stabilised by
cholesterol, with other stabilisers sometimes added to the mixture depending on the
specific use of the liposome.
• Phospholipids
• Cholesterol
• Polymers.
6.
7.
8. • Phospholipids:
• Major component
• Two types
• Synthetic: Examples DOPC: Dioleoyl phosphatidylcholine, DSPC: Disteroyl phosphatidylcholine, DOPE:
phosphatidylethanolamine, DSPE: Distearoyl phosphatidylethanolamine.
• Natural: most common is the phosphatidylcholine (PC) also known as lecithin. Originated from animal (hen
egg) and vegetable (soya bean). Other examples are phosphatidyl serine, phosphatidyl inositol,
ethanolamine.
• Cholesterol:
• Cholesterol and its derivatives are often included in liposomes for
• Decreasing the fluidity or micro viscosity of the bilayer.
• Reducing the permeability of the membrane to water soluble molecules.
• Stabilizing the membrane in the presence of biological fluids such as plasma.
9. • Polymers:
• Synthetic phospholipids with diacetylene group in the hydrocarbon chain polymerize
when exposed to U.V, leading to formation of polymerized liposomes having
significantly higher permeability barriers to entrapped aqueous drugs. E.g. for other
Polymerizable lipids are – lipids containing conjugated diene, methacrylate etc.
10. MECHANISM OF LIPOSOME FORMATION:
• The basic part of liposome is formed by phospholipids, which are amphiphilic molecule
(having a hydrophilic head and hydrophobic tail).
• The hydrophilic part is mainly phosphoric acid bound to a water soluble molecule, whereas,
the hydrophobic part consists of two fatty acid chains with 10 – 24 carbon atoms and 0 – 6
double bonds in each chain.
• When these phospholipids are dispersed in aqueous medium, they form lamellar sheets by
organizing in such a way that, the polar head group faces outwards to the aqueous region
while the fatty acid groups face each other and finally form spherical/ vesicle like structures
called as liposomes.
• The polar portion remains in contact with aqueous region along with shielding of the non-
polar part.
11. • When phospholipids are hydrated in water, along with the input of energy like sonication,
shaking, heating, homogenization, etc.
• It is the hydrophilic/ hydrophobic interactions between lipid – lipid, lipid – water molecules
that lead to the formation of bilayered vesicles in order to achieve a thermodynamic
equilibrium in the aqueous phase,
• The reasons for bilayered formation include:
• The unfavorable interactions created between hydrophilic and hydrophobic phase can be minimized
by folding into closed concentric vesicles.
• Large bilayered vesicle formation promotes the reduction of large free energy difference present
between the hydrophilic and hydrophobic environment.
• Maximum stability to supramolecular self assembled structure can be attained by forming into
vesicles.
12.
13. CLASSIFICATION:
• Based on the structural parameters.
• Unilamellar vesicles:
• Small unilamellar vesicles (SUV): size ranges from 20-40 nm.
• Medium unilamellar vesicles (MUV): size ranges from 40-80 nm.
• Large unilamellar vesicles (LUV): size ranges from 100-1000 nm.
• Oligolamellar vesicles (OLV): these are made up of 2-10 bilayers of lipids surrounding
a large internal volume.
• Multilamellar vesicles (MLV): they have several bilayers. They can compartmentalize
the aqueous volume in an infinite number of ways. They differ according to way by
which they are prepared.
14.
15. • Based on method of liposome preparation:
Type Size and made of
REV Single or oligolamellar vesicles made
by reverse-phase evaporation
method.
MLV-REV Multilamellar vesicles made by reverse
phase evaporation method.
SPLV Stable plurilamellar vesicles.
FATMLV Frozen and thawed MLV.
VET Vesicles prepared by extrusion
technique.
DRV Dehydration-rehydration method.
16.
17. • Based on composition and application:
Type Property
Conventional liposomes Neutral or negatively charged phospholipids and
cholesterol.
Fusogenic liposomes (RSVE) Reconstituted sendai virus envelops.
pH sensitive liposomes Phospholipid such as PE and DOPE with either
CHEMS or OA.
Cationic liposomes Cationic lipids with DOPE.
Long circulatory (stealth) liposomes
(LCL)
Neutral high Tc˚, cholesterol and 5-10% of PEG-
DSPE.
Immuno-liposomes CL or LCL with attached monoclonal antibody or
recognition sequence.
18.
19. METHODS OF LIPOSOMES PREPARATION:
• Two types:
• Passive loading technique: Loading of the entrapped agents before/ during the
manufacture procedure.
• Active loading technique: Certain types of compounds with ionizable groups & those
with both lipid & water solubility can be Introduced into liposomes after the
formation of intact vesicles.
20.
21. PASSIVE LOADING TECHNIQUE:
• These are classified into three types based on the modes of dispersion. They are:
• Mechanical dispersion methods
• Solvent dispersion methods
• Detergent solubilizing methods.
22. MECHANICAL DISPERSION METHODS:
• Lipid is solubilised 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 trapped in lipid vesicles.
• Types:
• Lipid film hydration by hand shaking, freeze drying or non-hand shaking
• Micro emulsification
• Sonication
• French pressure cell
• Membrane extrusion
• Dried reconstituted vesicles.
23. THIN FILM HYDRATION USING HAND SHAKING AND NON HAND SHAKING
METHODS:
• Lipids are casted as stacks of film from their organic solution using flash rotatory
evaporator under reduced pressure (or by hand shaking) and then casted film is
dispersed in an aqueous medium.
• Upon hydration the lipids swell and peel off from the wall of the RBF and
vesiculate forming MLVs.
• Mechanical energy required for the swelling of lipids and dispersion of casted
lipid film is imparted by hand shaking or by exposing the film to a steam of water
saturated nitrogen for 15 min followed by swelling in aqueous medium without
shaking.
24.
25. SONICATION:
• Most extensively used method for the preparation of SUV.
• MLVs are sonicated either with a bath type sonicator or a probe sonicator under a
passive atmosphere.
• Disadvantages:
• Very low internal volume/encapsulation efficacy.
• Degradation of phospholipids and compounds to be encapsulated.
• Elimination of large molecules.
• Metal pollution from probe tip.
• Presence of MLV along with SUV.
26. Probe sonicator:
• Tip of a sonicator is directly engrossed into the liposome dispersion.
• Energy input into lipid dispersion is very high results in local hotness.
• With the probe sonicator, titanium will slough off and pollute the solution.
Bath sonication:
• The liposome dispersion in a cylinder is placed into a bath sonicator.
• Controlling temperature usually easier in this method.
• The material being sonicated can be protected in a sterile vessel, dissimilar the
probe units, or under an inert atmosphere
27.
28. FRENCH PRESSURE CELL: EXTRUSION:
• Involves the extrusion of MLV through a small orifice.
• The size of liposomes is reduced by gently passing them through polycarbonate
membrane filter of defined pore size at lower pressure.
• Used for preparation of LUVs and MLVs
• French press vesicle appears to recall entrapped solutes significantly longer than
SUVs do, produced by sonication or detergent removal.
29. Advantages:
• Less leakage.
• More stable liposomes are formed compared to sonicated forms.
• Gentle handling of unstable materials.
Disadvantages:
• High temperature is difficult to attain.
• Working volumes are comparatively small (about 50 mL as the maximum).
30.
31. SOLVENT DISPERSION METHODS
• In this method, lipids are first dissolved in organic solvent, which is then brought
into contact with aqueous phase containing material to be entrapped in
liposome under rapid dilution and rapid evaporation of organic solvent.
• Types:
• ethanol injection
• ether injection
• double emulsion
• reverse phase evaporation vesicles
• stable pluri lamellar vesicles
32. ETHER INJECTION:
• 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.
• The main drawbacks of the method are population is heterogeneous (70-190 nm)
and the exposure of compounds to be encapsulated to organic solvents or high
temperature.
33. ETHANOL INJECTION:
• 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.
34.
35. REVERSE PHASE EVAPORATION:
• First water in oil emulsion is formed by brief sonication of a two phase system
containing phospholipids in organic solvent (diethylether or sopropylether or
mixture of isopropyl ether and chloroform) and aqueous buffer.
• The organic solvents are removed under reduced pressure, resulting in the
formation of a viscous gel.
• The liposomes are formed when residual solvent is removed by continued rotary
evaporation under reduced pressure. The method has been used to encapsulate
small and large macromolecules.
36.
37. DETERGENT SOLUBILIZING METHODS.
• In this method the phospholipids are brought into intimate contact with
aqueous phase via detergent which associate with phospholipids molecules and
serve to screen the hydrophobic portions of the molecules from water.
Detergent (cholate, alkyl glycoside, Triton x-100) removed from mixed micelles
by
• Dialysis
• Column chromatography
• Dilution.
38. BY DIALYSIS:
• The detergents at their critical micelles concentrations have been used to solubilize
lipids.
• As the detergent is removed the micelles become progressively richer in phospholipid
and finally combine to form LUVs.
• The detergents can be removed by dialysis.
• The advantages of detergent dialysis method are excellent reproducibility and
production of liposome populations which are homogenous in size.
• The main drawback of the method is the retention of traces of detergent(s) within the
liposomes.
39. GEL-PERMEATION CHROMATOGRAPHY:
• In this method, the detergent is depleted by size special chromatography.
Sephadex G-50, Sephadex G-l 00, Sepharose 2B-6B, and Sephacryl S200-S1000
can be used for gel filtration.
• The liposomes do not penetrate into the pores of the beads packed in a
column.
• At slow flow rates, the separation of liposomes from detergent monomers is
very good.
40. CHARACTERIZATION OF LIPOSOMES:
• Liposomes produced by different methods have varying physicochemical
characteristics, which leads to differences in their
• in vitro (sterilization and shelf life) and
• in vivo (disposition) performances.
41. SIZE AND SIZE DISTRIBUTION:
• When liposomes are intended for inhalation or parenteral administration, the size
distribution is of primary consideration.
• Various techniques of determing the size of the vesicles include:
• microscopy (optical microscopy, negative stain transmission electron microscopy ,
cryo-transmission electron microscopy, freeze fracture electron microscopy and
scanning electron microscopy ),
• Diffraction and scattering techniques (laser light scattering, and photon correlation
spectroscopy)and
• hydrodynamic techniques (field flow fractionation, gel permeation and
ultracentrifugation).
42. PERCENT DRUG ENCAPSULATION
• The amount of drug encapsulated/ entrapped in liposome vesicle is given by percent drug
encapsulation.
• The formulation consists of both free (unencapsulated) and encapsulated drug.
• Column chromatography can be used to estimate the percent drug encapsulation of liposomes.
• So as to know the exact amount of drug encapsulated, the free drug is separated from the
encapsulated one.
• Then the fraction of liposomes containing the encapsulated drug is treated with a detergent, so
as to attain lysis, which leads to the discharge of the drug from the vesicles into the surrounding
medium.
• This exposed drug is assayed by a suitable technique which gives the percent drug encapsulated
from which encapsulation efficiency can be calculated
43. • Trapped volume per lipid weight can also give the percent drug encapsulated in a
liposome vesicle.
• It is generally expressed as aqueous volume entrapped per unit quantity of lipid,
μl/μmol or μg/mg of total lipid.
• In order to determine the trapped volume, various materials like radioactive
markers, fluorescent markers and spectroscopically inert fluid can be used.
• % Encapsulation
• Drug entrapped in liposomes/ Total drug added x 100
44. SURFACE CHARGE:
• Charge on the liposome surface plays a key role in the in vivo disposition, it is
essential to know the surface charge on the vesicle surface.
• Two methods namely:
• free-flow electrophoresis
• zeta potential measurement.
• The surface charge can be calculated by estimating the mobility of the liposomal
dispersion in a suitable buffer (determined using Helmholtz– Smolochowski
equation)
45. VESICLE SHAPE AND LAMELLARITY
• Various electron microscopic techniques can be used to assess the shape of the
vesicles.
• The number of bilayers present in the liposome, i.e., lamellarity can be
determined using:
• Freeze fracture electron microscopy and
• 31P-Nuclear magnetic resonance analysis.
• The surface morphology of liposomes can be assessed using
• freeze-fracture and
• freeze-etch electron microscopy .
46. PHOSPHOLIPID IDENTIFICATION AND ASSAY:
• The chemical components of liposomes must be analyzed prior to and after the
preparation.
• To estimate the phospholipid concentration:
• Barlett assay , Stewart assay and thin layer chromatography can be used
• A spectrophotometric method is used to quantify total phosphorous, which
measure the intensity of blue color developed at 825 nm against water.
• Techniques can be used to determine the cholesterol concentration:
• Cholesterol oxidase assay or ferric perchlorate method and Gas liquid chromatography
47. STABILITY OF LIPOSOMES:
• The therapeutic activity of the drug is governed by the stability of the liposomes
right from the manufacturing steps to storage to delivery.
• A well designed stability study includes the evaluation of its physical, chemical
and microbial parameters along with the assurance of product’s integrity
throughout its storage period.
• Physical:
• morphology, size and size distribution of the vesicles are important parameters to
assess the physical stability.
• In order to monitor this, a variety of techniques like light scattering and electron
microscopy can be used to estimate the visual appearance (morphology) and size of
the vesicles.
48. • Chemical:
• Phospholipids are chemically unsaturated fatty acids that are prone to oxidation and
hydrolysis, which may alter the stability of the drug product.
• Indeed chemical reaction can be induced even by light, oxygen, temperature and
heavy metal ion
• Liposomes can be prevented from oxidative degradation by protecting them from
light, by adding anti-oxidants such as alpha – tocopherol or butylated hydroxyl
toluene (BHT), producing the product in an inert environment (presence of nitrogen or
Argon) or by adding EDTA to remove trace heavy metals
49. IN-VITRO DRUG RELEASE:
• In vitro drug release can be performed using the dialysis tube diffusion
technique.
• The dialysis bag membrane should be selected following screening of various
membrane, no drug adsorption may occur and the membrane should be freely
permeable to the active ingredient.
• The entire system is kept at 37 degree C under continuous magnetic stirring
and the receptor medium is closed to avoid evaporation of the dissolution
medium.
• Samples of the dialysate are taken at various time intervals and assayed for the
drug by HPLC, spectrophotometer or any other convenient method.
50. APPLICATIONS:
• As drug delivery carriers.
• Site-avoidance delivery
• Site specific targeting:
• Intracellular drug delivery
• Sustained release drug delivery
• Immunological adjuvants in vaccine
• In gene delivery.
• Enzyme replacement therapy.
• Chelation therapy for treatment of heavy metal poisoning.
• Liposomes in antiviral/anti microbial therapy.
• In multi drug resistance.
• In cosmetology