LIPOSOMES.pptx

The name liposome is derived from two Greek words: Lipo meaning “fat” and Soma meaning “body”.
Liposome are also defined as artificial microscopic vesicles consisting of aqueous compartment and surrounded by one or more concentric layer of phospholipid.
The sphere like interior encapsulates a liquid and also contain more substance like peptides, protein, hormones, enzymes, antibiotic, antifungal and anticancer agents.

1. LIPOSOMES Presented by Punith M M. Pharm, 2 nd Semester Molecular pharmaceutics(NTDS) Department of Pharmaceutics Acharya & BM Reddy College of Pharmacy, Bengaluru 1

2. INTRODUCTION The name liposome is derived from two Greek words: Lipo meaning “fat” and Soma meaning “body”. Liposome are also defined as artificial microscopic vesicles consisting of aqueous compartment and surrounded by one or more concentric layer of phospholipid. The sphere like interior encapsulates a liquid and also contain more substance like peptides, protein, hormones, enzymes, antibiotic, antifungal and anticancer agents. The size of a liposomes ranges from some 20nm up to several micrometers and the thickness of each phospholipid layer is about 4nm. 2

3. 3 Fig 1 :- Structure of liposome

4. COMPOSITION OF LIPOSOMES Liposome are most often composed of - phospholipid and cholesterol. Phospholipid- It is major structural component of liposome. It has the characteristic of excellent biocompatibility and amphiphilic in nature. There exists two sorts of phospholipid – Glycerophospholipids and sphingolipids. Examples of phospholipid:- Phosphatidyl choline (Lecithin) – PC, Phosphatidyl ethanolamine (cephalin) – PE, Phosphatidyl serine (PS), Phosphatidyl inositol (PI) and Phosphatidyl glycerol (PG). 4

5. Cholesterol - Cholesterol is one of the other components present in liposome. Cholesterol does not itself form bilayer structure but can be incorporated into phospholipid membranes in very high concentration. It acts as fluidity buffer. The concentration of cholesterol is affecting the particle size of liposome,   improving the stability of the vesicle and preventing the aggregation of molecules. 5

6. PROPERTIES OF LIPOSOMES Some of the properties of liposomes imparted due to their structural characterization and organization are: They are amphiphilic. They are permeable to water. Osmotically, they are sensitive. The liposomes with positively charged membranes are impermeable to cations, and those containing negative charges are relatively permeable to anions. 6

7. PHASE TRANSITION TEMPERATURE OF LIPOSOME Phase transition temperature (Tc) is temperature at which a membrane changes between the fluid and gelled state. Phase transition of lipid bilayer is a important property of liposome. Liposome with low Tc (less than 37°C) are fluid like and result leakage of drug content at physiological temperature. But, the high Tc (greater than 37°C) of liposomes is rigid and less leakage possibility at physiological temperature. The transition from one phase to another can be detected by technique like micro-calorimetry. 7

8. LIPOSOME CELL INTERACTION/MECHANISM The adsorption and endocytosis are the two main mechanisms for liposomes cell interaction. Liposomes can be adsorbed to a cell surface directly (non-specifically) or by specific interaction with a cell-surface receptor. To achieve specificity, liposomes can be derivatized with protein, antibody, or carbohydrates moieties or with other polymers. In endocytosis, the target cell internalizes the liposomes actively. In addition to adsorption and endocytosis, there are two other categories of liposome interaction with the cell surface; fusion of the cell with the vesicle, and lipid exchange. 8

9. ADVANTAGES OF LIPOSOMES Can carry both water and lipid soluble drugs. Non-ionic in nature. Liposome is biocompatible, completely biodegradable, non-toxic, and non-immunogenic. Suitable for delivery of hydrophobic, amphipathic and hydrophilic drug. Protect encapsulated drug from the external environment. Liposome reduces toxicity and increase stability via encapsulation. They are increase activity of chemotherapeutic drug. 9

10. 8) Biodegradable drug can be stabilized from oxidation. 9) Reduce exposure of sensitive tissues to toxic drugs. 10) Improve protein stabilization. 11) Control hydration. 12) Provide sustained release. 13) Targeted drug delivery or site specific drug delivery. 14) Can be administered through various routes. 10

11. DISADVANTAGES Production cost is high. Leakage and fusion of encapsulated. Short half-life. Stability problems. Allergic reaction may occur to liposome constituents. Problem to targeting to various tissues due to their large size. Phospholipid undergoes oxidation, hydrolysis. 11

12. CLASSIFICATION OF LIPOSOMES Classification of liposome depending upon size and shape Multilamellar vesicles (MLV) Large unilamellar vesicles (LUV) Small unilamellar vesicles (SUV) 2) Classification of liposome according to composition Conventional liposome pH- sensitive liposome c) Cationic liposome d) Long circulating/Stealth liposomes 12

13. e) Immuno- liposome f) Transferosomes g) Ethosomes h) Virosomes i ) Archaeosomes j) Multivesicular Liposomes 3) Classification of liposome depending upon production method Passive loading technique B) Mechanical/Physical dispersion technique a) Sonication b) Lipid hydration by hand shaking or freeze drying 13

14. c) Micro emulsification d) French pressure cell e) Membrane extrusion f) Dried reconstituted vesicles (DRVs) g) Fusion method h) Freeze and thaw extrusion method (FAT) C) Solvent dispersion technique a) Ether injection b) Ethanol injection c) De-emulsification method d) Rapid solvent-exchange method 14

15. e) Double emulsion method f) Reverse phase evaporation D) Detergent removal technique E) Active loading technique 15

16. 1) DEPENDING UPON SIZE AND SHAPE a) Multilamellar vesicle (MLV) - Multilamellar vesicle are generally size between '100- 1000 nm' and it consist of two or more than two bilayers. The method of preparation of multilamellar vesicle is very simple, which include in thin- film hydration method/ hydration of lipids in excess of organic solvent. They are very long storable because they are mechanically stable. It is rapidly cleared by " Reticulo -Endothelium System" (RES) cell. b) Large unilamellar vesicle (LUV) - The large unilamellar vesicles of liposome consist of a single bilayer or single lamella. LUV size is > 100 nm and can reach size up to 1000 nm. 16

17. They have mainly high efficiency of encapsulation, since ability to hold large volume of solutions in their cavity. They are similar to multilamellar vesicle. Large unilamellar vesicles are prepared from various methods like ether injection, reverse phase evaporation technique and detergent dialysis. c) Small unilamellar vesicle (SUV) - Small unilamellar vesicles are generally smaller size (< 50 nm) as compared to multilamellar vesicle and large unilamellar vesicle. Small unilamellar vesicles contain single bilayer. SUV are prepared from solvent injection method (ethanol and ether injection). 17

18. 18 Fig 2 :- Liposomes classification based on size and shape

19. 2) CLASSIFICATION OF LIPOSOME DEPENDING UPON COMPOSITION/ LIPOSOME DERIVED VESICLES a) Conventional liposome Conventional liposome is composed of natural phospholipid or lipid such as sphingomyelin, egg phosphatidylcholine. Liposome containing positive and negative charge have been reported to have shorter half- lives, toxic and rapidly remove from systemic circulation. These liposomes are mainly use for targeting of the 'Reticuloendothelial system'(RES). Conventional liposome is used mostly as compare to other types because it has shorter circulation times. To increase circulation time, liposome surface can be coated with a hydrophilic polymer. 19

20. b) pH- sensitive liposome pH- sensitive liposome is composed of oleic acid (OA), phosphatidyl ethanolamine (PE), cholesterol hemisuccinate (CHEMS). pH- sensitive liposomes are stable at physiological pH (pH- 7.4) pH- sensitive liposomes are lipid composition that can be destabilized when the external pH is changed from neutral or slight alkaline pH to an acidic pH. In cell culture pH sensitive liposome can increase the delivery of proteins, fluorescent markers, cytotoxic substance, RNA and DNA into the cytoplasm. 20

21. c) Cationic liposome Cationic liposomes are composed of dimethyl- dioctaatidecyl ammonium bromide (DDAB), 1,2-di mrystyloxypropyl-3-dimethyl-hydroxethyl ammonium bromide (DORIE) combined with dioleoylphosphatidyl ethanolamine (DOPE) etc. These liposomes are highly toxic and have short lifespan, thus limited to local administration. They are mostly use for delivery of macromolecules (negatively charge) and delivery of DNA and RNA. 21

22. d) Long circulating liposome (Stealth liposomes) These are the carrier systems that can avoid phagocytosis and, thus circulate longer in the blood. Long circulating liposome are prepared by coating liposome surface with a hydrophilic layer of oligosaccharides, glycoproteins, synthetic polymers, which prevent opsonization. Long circulating liposome are widely use in biomedical in-vitro and in-vivo studies and clinical practice. The liposome is very useful tools, especially for tumor targeting therapy. Long circulating liposome exhibit dose-independent, non-saturable, long-linear kinetics and increased bioavailability. 22

23. e) Immuno-liposome (ILs) This is a class of lipid vesicles designed for active targeting of their encapsulated/entrapped material inside the body. The ILs posses moieties such as antibodies, carbohydrates and hormones on the outer surface of their membrane. Recently, ILs have been used for gene targeting to human brain cancer cells, which has resulted in a 70-80% inhibition in cancer cell growth. 23

24. f ) Transferosomes Deformable liposomes (Transferosomes®) are the first generation of elastic vesicles. They generally consist of phospholipids, cholesterol and additional surfactant molecules, such as sodium cholate. Transferosomes are ultradeformable and squeeze through pores less than one-tenth of their diameter. g ) Ethosomes These are high ethanol containing vesicles, most widely used in transdermal or topical delivery due to its physicochemical characteristics, more efficiently across the skin barrier and reach into the systemic blood circulation. 24

25. h) Virosomes Virosomes or artificial viruses are one type of liposome that contain reconstituted viral proteins in their structure. Unlike viruses, virosomes are not able to replicate but are pure fusion-active vesicles. Due to the presence of the specialized viral proteins on the surface of virosomes, they can be used in active targeting and delivery/controlled release at the desired /specific/target site. Viruses have developed the ability to fuse with the cells during the course of evolution, thus allowing for release of their contents directly into the cells. Ex: Epaxal is an aluminium-free vaccine based on formalin-inactivated hepatitis A (strain RG-SB) antigen incorporated virosomes. 25

26. i) Archaeosomes They are defined as liposomes made from one or more of the polar ether lipids extracted from the domain Archaea (Archaeobacteria). Many archaea live in environments including high salt concentration or low pH values and high temperatures. Hence, their membrane lipids are unique and enable them to survive in such hostile conditions. j) Multivesicular Liposomes They are composed of several small vesicles entrapped by a single lipid bilayer. MVLs prepared by a multiple emulsion method possess a unique structure of multiple, non-concentric, aqueous chambers surrounded by a network of lipid membrane. 26

27. 3) CLASSIFICATION OF LIPOSOMES DEPENDING UPON PRODUCTION METHOD A) Passive loading technique Passive loading is in which liposome are formed concurrently with drug loading. In that hydrophilic compounds are distributed homogeneously in the aqueous phase (both inside and outside the liposomes) and hydrophobic drugs are retained inside the lipid bilayer of liposome. 27

28. B) MECHANICAL/PHYSICAL DISPERSION TECHNIQUE a) Sonication Sonication is a process in which sound waves are used to agitate particle in solution. Such disruption can be used to mix solutions, speed the dissolution of a solid into a liquid and remove dissolved gas from liquid. Sonication is method in which MLVs are transformed to small unit lamellar vesicles (SUVs). The ultrasonic irradiation is provided to convert MLVs to SUVs. There are two method used, 28

29. 1) Bath sonication method The liposome dispersion in a cylinder is placed into a bath sonicator. Controlling the temperature of the lipid dispersion is usually easier. 2) Probe sonication method The tip of a sonicator is directly engrossed into the liposome dispersion. The energy input into lipid dispersion is very high. The coupling of energy at the tip results in local hotness, the vessel must be engrossed into a water/ice bath. 29

30. 30 Fig 3 :- Probe sonication Fig 4 :- Bath sonication

31. b) Lipid film hydration It is the most widely used method for the preparation of MLVs and can be performed in two steps:- Step (1) - Lipid hydration by hand shaking The lipids are dissolved in chloroform: methanol (2:1 v/v) solvent mixture. Then introduce into a round bottom flask. This flask is attached to rotary evaporator (rotated at 60 rpm). The organic solvent is evaporated at about 30° C or about transition temperature of lipid. The evaporator is placed in vacuum source to eliminate residual organic solvent. Remove the flask from the evaporator and place on ice to obtain thin lipid film and lyophilize until dry. 31

32. Step (2) - Hydration of lipid layer After removal from lyophilizer , 5ml saline phosphate buffer is added. The flask is again attached to evaporator. The evaporator are rotated at room temperature and pressure at same speed (for below 60 rpm). The flask is rotated for 30 minute or until all lipid has been removed from the wall of the flask and has given homogeneous milky suspension. The suspension is allowed to stand for 2 hours at room temperature or at a temperature above transition temperature of the lipid in order to complete the swelling process to give MLVs (Multilamellar vesicle). 32

33. 33 Fig 5 : - Lipid film hydration

34. c) Microemulsification SUVs can be prepared from concentrated lipid suspension by the use of a microfluidizer. It yields liposomes with good aqueous phase encapsulation. The vesicle dispersion is forced in microfluidizer pump through a 5µm screen at very high pressure. Subsequently, vesicle dispersion is forced through specific micro channels, which direct two streams of vesicle dispersions to strike at right angles with very high velocity. The vesicle dispersion collected can be used again in the pump and interaction chamber until spherical vesicles are achieved. 34

35. 35 Fig 6 : - Microemulsification using microfluidizer

36. d) French pressure method This method is used to disrupt the plasma membrane of cells by passing them through a narrow valve under high pressure (20,000 psi at 40°c). This method used to preparation of 1-40 ml of homogeneous unilamellar liposomes of intermediate size (30-80 nm). This liposome is more stable compared to the sonicated liposomes. This method has some drawbacks which are, initial high cost for the pressure cell. Liposome prepared by this method have less structural defects compared to sonicated liposome. 36

37. 37 Fig 7 : - French pressure cell

38. e) Membrane extrusion Lipid suspension is forced through a polycarbonate filter of a defined pore size to yield particles having a diameter near the pore size of the filter used. Prior to extrusion through the final pore size, LMV are disrupted either by several freeze-thaw cycles or by prefiltering the suspension through a larger pore size. This method improves the homogeneity of the size distribution of the final suspension. The extrusion should be done at a temperature above the Tc of the lipid. 38

39. 39 Fig 8 : - Membrane extrusion

40. f) Dried reconstituted vesicles This method involves freeze drying the dispersion of empty SUVs, followed by rehydration with the aqueous fluid, which have material to be entrapped giving rise to dispersion of solid particles in finely subdivided form. Advantages - High entrapment of water soluble component and use of gentle situation for preparing liposomes. This method id appropriate only for SUVs, since there is low rate of incorporation of MLVs. g) Fusion method In this process, fusogenic agents are used for fusion of SUVs for increasing the entrapment efficiency. This method allows the protection of lipid and entrapped material from harmful physicochemical environment. 40

41. Alteration in the pH increases the surface charge density of lipid bilayer and brings on spontaneous vesiculation. Aggregation can also be induced by using calcium. h) Freeze and thaw extrusion method (FAT)  In this method, liposomes formed using the thin-film method are vortexed with the material needed to be incorporated in the vesicles. This is done until the whole lipid film is suspended. Then, the resulting vesicles are frozen in warm water and vortexed again. This is the most preferable technique when it comes to the formation of multilamellar vesicles or increasing the encapsulation efficiency of the liposomes. 41

42. C) SOLVENT DISPERSION METHOD Firstly, dissolving the lipid and other constituents of the liposome membrane in other solution(organic solvent). Then, the aqueous phase is added to resulting solution. In this aqueous phase contain material which is to be entrapped. Solvent dispersion method involving ether injection method, ethanol injection method, and reverse phase evaporation method. Ether injection method Solution of lipid is dissolved into ether or diethyl ether or methanol mixture. 42

43. These mixtures are slowly injected into aqueous solution of the material to be encapsulation at 55-65°C or under reduce pressure. Then ether is removed with the help of vacuum leads to formation of liposome. b) Ethanol injection method This is simple method. In this method an ethanol solution of the lipid is directly injected rapidly to an excess of saline through a fine needle. The rate of injection is kept enough to attain absolute and rapid mixing; subsequently ethanol is diluted immediately with water. This leads to equal dispersion of phospholipids throughout the medium. This procedure yields a high proportion of SUVs (about 25 nm diameter). 43

44. 44 Fig 9 : - Ethanol and ether injection method

45. c) De-emulsification method Involves formation of first the inner leaflet of bilayer, followed by outer half. Aqueous medium comprising material to be entrapped is added into higher volume of immisicible organic solution of lipid. This leads to formation of w/o emulsion, which is subsequently agitated mechanically to break aqueous medium into microscopic water droplets ; the droplets are stabilized by means of phospholipid monolayer on the interface. 45

46. d) Rapid solvent-exchange method This method involves the rapid transfer of lipid mixture between pure solvent and pure aqueous environment. The lipid solution in organic solvent is passed through an orifice of syringe by means of vacuum into a tube containing aqueous buffer, which is placed on a vortexer . Before coming in contact with aqueous phase, the organic solvent gets vaporized due to vacuum and eliminated very rapidly in few seconds. Simultaneously, the lipid mixture also precipitates in aqueous buffer very quickly. 46

47. e) Double emulsion method The organic solution containing water droplets (w/o) is brought in contact with an excess of aqueous medium, followed by mechanical dispersion, which results in phase inversion and formation of multi-compartment vesicles takes place (w/o/w). These vesicles are suspended in aqueous medium, in which the two aqueous compartments are separated from each other by means of two phospholipid monolayers. The hydrophobic surfaces of monolayers face each other transversely by a thin film of organic solvent. Elimination of the organic phase causes formation of intermediary sized unilamellar vesicles. 47

48. f) Reverse phase evaporation method The mixture of two phases is subjected to bath sonication. It contains phospholipid in organic solvent(diethyl ether) and aqueous buffer. The droplets, thus formed, are dried down to a semi-solid gel under reduced pressure by a rotary evaporation. The monolayers of phospholipid at this stage surround each water compartment, which is closely opposed to each other. This is followed by mechanical shaking with the help of vortex shaker causing collapse of certain water droplets. During this process, the lipid monolayer, which enclosed the collapsed vesicle, becomes the part of adjacent vesicle to form outer leaflet of bilayer of LUVs. Dispersion medium for this newly formed liposomes is provided by the aqueous content of collapsed droplets. 48

49. 49 Fig 10 : - Reverse phase evaporation method

50. D) DETERGENT SOLUBILIZATION/ REMOVAL METHOD In this, the phospholipids are bought in intimate contact with the aqueous phase via detergents, which associate with phospholipids molecules. The structures formed due this association are called as ‘micelles’. Upon removal of detergent, LUVs may be formed (Homogenous size liposomes are obtained). The shape and size of the micelles depends on the chemical nature of the detergent, concentration and other lipids involved. Critical Micelle Concentration (CMC) is the concentration of detergent in water at which micelles begin to form. Below CMC detergent molecules remains in free solution. Detergent removal is done by dialysis system, gel chromatography using Sephadex G-25 column, adsorption/binding of triton x-100 and binding of octyl glucoside. 50

51. E) ACTIVE LOADING TECHNIQUE In this method, internalization of preformed liposomes is typically driven by a trans-membrane pH gradient. The pH surrounding the liposome allows some of the drug to remain in unionized form, hence, allowing it to migrate across the bilipid layer. Once, inside the liposomes, the drug becomes ionized and gets entrapped here due to the difference in pH. 51

52. Advantages of active loading method over passive encapsulation techniques are- • A high encapsulation efficiency and capacity. • A reduced leakage of encapsulated compounds. • Limited chemical degradation during storage. • Avoidance of biological active compounds during preparation steps in the dispersion thus reducing safety hazards. 52

53. EVALUATION OF LIPOSOME Physical characterization: - Physical characterization evaluates various parameters include size, shape, surface features, release profile and phase behaviors. Chemical characterization: - It includes study of purity and potency of various lipophilic constituents. Biological characterization: - They are useful in safety and suitability of formulation for therapeutic application. 53

54. 54 Table 1 : - Characterization of liposomes

55. STABILITY OF LIPOSOMES The stability can be determined by storage under the following conditions:- Highest and lowest temperatures likely to be encountered, for one month Room temperature for 12-24 months Two or three freeze-thaw cycles (20-25°C) 60 cycles/min on a reciprocating shaker for 24-48 hrs Six to eight heat-cool cycles (5-45°C, 48 hrs at each temperature) Visual or microscopic examinations After storage at these conditions, the liposomes are evaluated for the residual drug content, vesicular size and shape and number of vesicles per cubic mm. 55

56. APPLICATION 1) Site-specific drug delivery:  Liposomes are suitable vehicles for drug delivery at targeted locations. To form a site-specific drug delivery system, they are combined with opsonins and ligands, such as antibodies, sugar residues, apoproteins, or hormones, which are tagged on the lipid vesicles. This also helps in reducing drug-related toxicity. 2) As artificial blood surrogates: Liposome encapsulated haemoglobin products are being investigated as artificial RBCs (oxygen carrying RBCs substitutes). Sterically stabilized liposomes bearing haemoglobin are better than conventional liposomes encapsulating haemoglobin. These systems have manifest toxicity, less platelet activation and aggregation and less haemostatic generation. 56

57. 3) Treatment of parasitic diseases and infections:  Liposomes serve as an ideal carrier to deliver the drugs to treat parasitic diseases, especially those that infect monocytes and macrophages cells, like leishmania. 4) Agriculture industry:  Liposomes can entrap unstable compounds such as antimicrobials, flavors, antioxidants, and bioactive elements and protect them from a variety of environmental and chemical changes, such as enzymatic chemical changes, ionic strength variations, and temperature change. Thus, they are used to develop new flavors, control flavor release, improve food color, and modify the texture of food components. It also ensures the release of the ingredients at the desired time. 57

58. 5) HIV (human immunodeficiency virus) infection treatment:  Liposomes can encapsulate anti-HIV nanocarriers, like antiretroviral nucleotide and other antiviral drugs, and deliver them to specific sites. 6) Transdermal drug delivery:  The main challenge in transdermal drug delivery is the penetration of macromolecules and hydrophilic drugs through the stratum corneum (outer layer of the skin). Liposomes have a similar molecular composition as lipid layers and have high permeability. Thus, they are a suitable carrier for the delivery of drugs penetrating the skin. 7) Enzyme immobilization: Liposomes can deliver the enzymes to the lysosomal system or to the other sites. β -glucosidase and α -glucosidase can be immobilized in liposomes, for the treatment of Gaucher's disease (lysosomal storage disease) and Pompe or acid maltose disease (glycogen storage disease type II), respectively. 58

59. 8) Liposomes in ocular delivery Liposomes are also used in ocular delivery because they are capable in developing intimate contact with ocular tissues (cornea and conjunctiva) and hence, provide higher drug absorption. Liposomes also provide protection to the drug from metabolic enzymes present in tear and/or at corneal epithelium and also improved ocular bioavailability and patient compliance by reducing dosing frequency. Liposomes can deliver both hydrophilic and lipophilic drugs, such as Pilocarpine, Ofloxacin, Diclofenac sodium, Ganciclovir and Chloramphenicol. The cationic surface charge liposomes exhibit excellent corneal uptake in comparison to anionic and neutral liposomes. 59

60. 9) Tumour therapy Liposome delivery systems offer the promising potential to enhance the therapeutic index of anticancer drugs, either by increasing the drug concentration in tumour cells or by decreasing the exposure in normal host tissues. Liposomes can be injected intravenously. When they are modified with lipids, which render their surface more hydrophilic, their circulation time in the bloodstream can be increased significantly. In this form they can extravasate to the tumour vascular endothelium. These so-called “stealth liposomes” are especially being used as carriers for hydrophilic (water soluble) anticancer drugs like Doxorubicin, Mitoxantrone and others. The Myocet (Metastatic breast cancer) and Doxil ® are the two first approved liposomal formulations and both contain doxorubicin but differ particularly the presence of Polyethylene glycol (PEG) coating. 60

61. 61 Compound Target Company TLC ELL-12 Various solid tumours Liposome Company Inc., Princeton, New Jersey Ambisome Fungal infection Gilead Sciences, Foster City, California (CA) Caelyx Metastatic breast and ovarian cancer North Ryde, New South Wales LipoTaxen Lung, breast and ovarian cancer Lipoxen , London, UK Lipo-DOX® Kaposi’s sarcoma Sun Pharma Advanced Research Centre, Vadodra , India VincaXome Solid tumours NeXstar , California, USA Depocyt Cancer therapy Skye Pharm, London, UK Table 2 : - Liposome formulations for tumour therapy

62. 10) Liposomes as vaccine carriers: Liposomes potentiate both cell-mediated and humoral immunity. Their advantages against other adjuvants (detoxified cholera toxins, alum) can be summarized as: (1) non-toxic, biocompatible and biodegradable; (2) incorporate other adjuvants to provide strong immune response; (3) convert loaded non-immunogenic substances into immunogenic ones; and (4) minimize or eliminate toxicity of toxic antigens and allergic reactions to allergic patients. Liposomal vaccines investigated to date are based on immunopotentiating reconstituted influenza virosome (IRIV). For immunopotentiation, immunomodulating agents such as muramyl dipeptide, lipopolysaccharide and lipid can be incorporated into liposomes. 62

63. 63 Product Target Company HepaXen Hepatitis B Lipoxen , London, UK LipoNeu Streptococcus pneumoniac causing meningitis Lipoxen , London, UK LipoRab Rabies Lipoxen , London, UK Stimuvax Cancer cells Biomira Inc., Edmonton, Canada Influenza vaccine Influenza virus Crucell , Leiden, Netherlands Avian retrovirus Chicken pox Vineland lab, Vineland, New Jersey, USA E. coli vaccine Escherichia coli Novavax, Rockville, USA New castle disease vaccine New castle disease IGI, Vineland Lab, New Jersey, USA Shigella flexneri 2A vaccine Shigella flexneri 2A infections Novavax, Rockville, USA Table 3 : - Liposome formulations as vaccine carriers

64. 11) In gene delivery Lipid based systems, polymers, peptides and liposomes are non-viral gene delivery vehicles. Among liposomes pH sensitive liposomes, cationic liposomes, fusogenic liposomes, genosomes , lipoplex and lipopolyplex seem to have gene delivery potential. The cationic liposomes deliver the content through membrane fusion thereby avoiding lysosomal and nucleolus degradation of DNA. Some of the widely used cationic liposomal formulations are Lipofectin , Lipofectamine, Transfectase , Cytofectin and Transfectam . The pH-sensitive liposomes exploit the endosomal acidification to promote fusion with endosomal memebranes . 64

65. Genosomes are the complex formulations of DNA with various cationic liposomes (lipoplex). Lipoplex has the tendency, to form aggregate with DNA to form large and heterogeneous particles at high concentration. To overcome this limitation, lipopolyplex formulations composed of liposomes poly-cation/DNA are devised. Liposomal DNA vaccination is one of the fast emerging as well as rewarding areas. 12) As radiopharmaceutical and radio diagnostic carriers Liposomal radio-diagnostic applications include liver and spleen imaging, lymphatic imaging, tumour imaging, blood pool imaging, imaging cardiovascular pathologies, visualization of inflammation and infection sites, brain visualization of bone marrow and eye vasculature. Liposome based imaging agents have already been successfully used for magnetic resonance, computed tomography and ultrasound imaging of tumours . 65

66. 13) Cosmetics and dermatology Liposomes carrying skin-care material is an excellent addition to the daily skin-care programs. Liposomes, when combined with essential oil, provide an effective nourishing treatment that penetrates deeply into the skin. Liposomes based anti-ageing topical formulations (creams, lotions, gels and hydrogels) have been formulated and launched in the cosmetic market in 1986 by L'Oreal in the form of niosomes and then by Christian Dior in the form of liposomes. Liposomal preparations reduce the skin roughness because of its interaction with corneocytes and of the intercellular lipids resulting in skin softening and smoothening. 66

67. Success rates of these products range between 83-98%, when parameters, such as tightening and firming effects, texture, smoothness, vitality, complexion, luminosity and clarity are concerned. Various liposome based formulations for facial and body care, make-up, mascara and foundations, hair care, self-tanning and sunscreen products and perfumes are likely to be launched soon in the market. 67

68. 68 Product/system Company Use Capture TM R60/80 Christian Dior, Paris, France Skin care and rejuvenation Plenitude TM L’Oreal , Paris, France Skin care and rejuvenation Inovi Pharm/ Apotheke , Gandijeva , Beograd Skin care and nourishment Coatsome NC TM NOF America Corp. America Humectant Nactosomes TM Lancome ( L’Oreal ), Paris, France Rejuvenation and nourishment Nyotran TM Aronex Pharm, Texas, USA Systemic fungal infection Mikasome ® NeXstar , California, USA Bacterial infection Table 4 : - Liposome formulations in cosmetics

69. REFERENCES Admin. A CONCISE REVIEW ON LIPOSOMES DRUG DELIVERY SYSTEM [Homepage on the Internet]. PharmaTutor . Available from: https://www.pharmatutor.org/articles/a-concise-review-on-liposomes-drug-delivery-system Singh A. Liposomes: Structure, Classification, and Applications [Homepage on the Internet]. Conduct Science. 2022;Available from: https://conductscience.com/liposomes-structure-classification-and-applications/ N. K. Jain, Introduction to NOVEL DRUG DELIVERY SYSTEMS. 69

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