liposome and nanotechnology
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List of contentso Introduction: o Advantages with use of liposomes as drug delivery system. o Classification o Manufacturing of liposomes o Liposome characterization and control
o Stability consideration for liposomal formulationso Regulatory science of liposome drug products o Drug release from liposomes o Applications o Recent innovations o Approved liposome products o References
INTRODUCTIONo The preparation of liposomes, with entrapped solutes, was demonstrated for the first time in 1965 by Prof. A.D. Bangham of the United Kingdom.
Definitiono Liposomes are microscopic spheres made from fatty materials, predominantly phospholipids. o made up of one or more concentric lipid bilayers, and range in size from 50 nanometers to several micrometers in diameter
Advantages with liposomeso Suitable for delivery of hydrophobic, hydrophilic and amphipatic drugs and agents o Chemically and physically well characterized entities o Biocompatible o Suitable for controlled release o Suitable to give localized action in particular tissues. o Suitable to administer via various routes
Classificationo Classification based on size of liposomes o Classification based on method of preparationo Classification based on composition and in vivo application
Classification based on sizeSmall unilamellar vesicles Medium sized unilamellar vesicles Large unilamellar vesicles Giant unilamellar vesicles Unilamellar vesicles Oligolamellar vesicles Multilamellar large vesicles Multivesicular vesicles
Classification based on method of preparationo o o o Vesicles prepared by extrusion method. Vesicles prepared by French press. Vesicles prepared by fusion. Vesicles prepared by reverse phase evaporation. o Frozen and thawed MLV. o Dehydration and rehydration vesicles. o Stable plurilamellar vesicles.
Classification based on specific propertieso Conventional Liposomes
Long circulating liposomes (Stealth Technology)o PEG coating o Low permeability liquid matrix and internal aqueous buffer system
Targeted liposomeso Target specific ligands, such as antibodies, immunoglobulins, lectins and oligosaccharides attached to the surface
Cationic Liposomeso Cationic lipid component interact with negatively- charged DNA o Results into Lipid DNA Complexes
Temperature sensitive liposome
PH sensitive Liposomes
MANUFACTURING OF LIPOSOMES
Materials used in preparation of liposomeso o o o o o o o Phospholipids Synthetic Phospholipids Glycerolipids Sphingolipids Glycosphingolipids Steroids Polymeric material Charge-inducing lipids
Structure of phospholipids
Issues to consider when selecting lipids.o o o o o o Phase transition temperature Stability Charge Lipid mixtures Cholesterol Source
Preparation of LiposomesMechanism of Vesicle Formationo The budding theory o The bilayer phospholipids theory
The budding theoryo Stress induced hydration of phospholipids o Organization in to lamellar arrays o Results in to budding of lipid bilayer leading to down sizing
The bilayer phospholipids theoryo Liposomes are formed when thin lipid films are hydrated o The hydrated lipid sheets detach during agitation and self-close to form large, multilamellar vesicles (LMV)
Method of Liposome Preparation
Conventional liposome preparation methodsPhospholipids Cholesterol Antioxidant Lipid component compounding Lipid solvent
Drug ,Salt Antioxidant Buffer WFI
Filter Solvent recovery Solvent removal
Hydration Extrusion Down sizing
Free drug recovery
Free drug removal Prefilter Sterile filter Vial filling
Lyophollization Seal / package
Method for preparation of (SUV)o o o Sonication High shear fragmentation Solvent injection methodo Injection of water immiscible solvent.o o Ether infusion. Fluorocarbon injection.
Injection of water miscible solvent.o o Ethanol injection Modified ethanol injection method
High shear fragmentationPiston
Rubber-O-ring Aqueous samples Pressure relief valve
Closure plugFig. French pressure cell Outlet
Solvent injection method.Vacuum pump Mix Aqueous phase Ether/lipid solution Gasket Mechanical drive Infusion pump
Temperature Controlled bath
Large and Intermediate sized unilamellar vesicles.o Methods used to prepare LUV and IUVo o o o o o Detergent dialysis Water in oil emulsion technique Freeze thaw cycling Slow swelling in non electrolytes Dehydration followed by rehydration Dilution or dialysis of lipids in the presence of chaotropic ions.
Reverse phase evaporation technique.
Lipid in solvent solution
Water in oil emulsion
High pressure extrusion.
Methods for controlling liposome sizeo Fractionationo Centrifugation o Size exclusion chromatography
o Homogenizationo Capillary pore membrane extrusion o Ceramic extrusion
Liposome characterization and controlLiposomesCharacterized by Size Number of lamellae Determined by Preparation Raw materials Protection Charge Stability
Degree of saturation
Presence of sterols
Physical characterization parameterso Mean size and size distribution o Number of lamellae o Osmotic behavior and entrapped volume o Internal distribution of drug
o Structural and motional behavior of lipidso Electrical surface potential & Surface PH
Stability considerationo Stabilization aspect for physical instability of liposomes o Chemical stability o Biological stability of liposomes
Regulatory aspectso Safety concerns: liposome formulationo Lipid toxicity (RBC lysis) o Presence of protein and lipoprotein for natural lipids o Residual solvent o Overload of RES o Particle sizeo (tail above 1 um) - Blockage of capillaries o Size affects RES uptake and tissue targeting
o Stability: shelf-live and in vivo o Dose dumping (via protein binding) o Sterility
Drug release from liposomeso The lipid bilayer of the liposome can fuse with other bilayers (e.g. cell membrane) thus delivering the liposome contents.
Liposome Performance In Vitro Release and Stabilityo In vitro drug release from liposomal systems was determined using dialysis sacks.
o Release test for a targeted liposome would need to show that liposome is stable until uptake at the site.
Factors affecting release of drugo o o o o o o o o Solvents pH Temperature Agitation Enzymes Cell culture Sink conditions Volume Sampling interval
Applicationso Liposomes as Protein Carriers in Immunology o Oral Drug Delivery o Site Specific Delivery o Sustained or Controlled Delivery o Gene Therapeutics
Innovations in vesicular drug delivery systemso Provesicles in drug delivery systemso o o o o Provesicles in drug delivery systems Proliposomes :Dry granular liposomes Mixed micellar proliposomes Protransferosomes
Characterization of provesicular systemo Morphology
Angle of reposeSize and size distribution Rate of hydration
oo o o
Entrapment efficiencyDegree of deformability and permeability measurement In vitro release rate In vivo fate and pharmacokinetic
Lipopolyplexeso A combination of DNA, polymers and liposomes o This method has resulted in better gene transfer and lower toxicity as compare to cationic liposomes
Transferosomeso Modified liposomes developed to increase the transdermal permeation of drug o Deformability is achieved by using surface active agent in proper ratioo Concentration of surfactant is very crucial
Ethosomeso Composed of phospholipids & alcohol ( ethanol or IPA) o Sometimes polyols or glycols in relatively high concentration & watero Better membrane permeability
o Discomeso Virosomes o Emulsomes
Cochleateso Cochleates are cigar-like microstructures o Consist of a series of lipid bilayers which are formed as a result of the condensation of small unilamellar negatively charged liposomes.
Depofoam technologyo Depofoam particles include hundred of bilayer enclosed aqueous compound. o Formed by first emulsifying a mixture of an aq phase containing the compound to be encapsulated & an organic phase containing lipid.
Niosomeso Nonionic surfactant vesicles(NSV) o Niosomes are formed from the self assembly of non-ionic amphiphiles in aqueous media resulting in closed bilayer.
Preparation of Liposomes by dry film methodo Lipids and drug dissolved in CHCl3 and evaporated to form thin film o Film is hydrated with buffer solution o Sonicated to form large unilamellar vesicles
Preparation of Liposomes by dry film methodLipid + drug + CHCl3Rotary evaporation
Approved liposome products marketed in US
Doxil Daunoxome Ambisome
Daunorubicin Daunorubicin Amphotericin B
Alza Corporation Gilead sciences ,,
Kopasi sarcoma ,, Serious fungal infection
Approved lipid complex products Ambelcet Amphotec Amphotericin B Amphotericin B Alza corporation Elan corporation