liposomes.pptx

Definition of liposomes?
Composition of liposomes
Types of liposomes
Preparation of liposomes

1. Liposomes & Drug Delivery Represented by : Amira Moustafa

2. Main topics Definition of liposomes? Composition of liposomes Types of liposomes Preparation of liposomes

3. Definition Liposome is an artificial sphere shape phospholipid vehicle consisting of one or more phospholipid bilayer with or without cholesterol used for drug delivery applications . C omposition It consists of one or more phospholipid bilayer surrounding aqueous core .

4. Phospholipid Bilayer Phospholipid bilayer may be natural lipids ( from natural source like soya bean or egg yolk) or synthetic lipids (ex: dimyristoyl phosphatidylcholine (DMPC) , distearoyl phosphatidylcholine (DSPC) . - Natural lipids are less stable than synthetic lipids Polar head of phospholipid may be choline (phosphatidyl choline ) or glycerol ( phosphatidyl glycerol ) or ethanolamine ( phosphatidyl ethanolamine )

5. Cholesterol can fill in the gaps left by the imperfect packing of other lipid species in liposomes so it used for stabilizing the liposome structure.

6. Drug entrapment in liposomes - H ydrophobic drug (incorporated in phospholipid bilayer) - Hydrophilic drugs ( loaded in the core) - Proteins & Genetic material ( loaded in the core )

7. Critical Phase Transition Temperature (Tc) of phospholipids The phase transition temperature is defined as the temperature required to induce a change in the lipid physical state from the ordered gel phase, where the hydrocarbon chains are fully extended and closely packed, to the disordered liquid crystalline phase, where the hydrocarbon chains are randomly oriented and fluid. Depending on the lipid Tc, membranes composed of different lipids can exhibit different fluidity levels at the same temperature. <Tc (phospholipids are more stable & impermeable ) >Tc ( phospholipid are less stable)

8. The Cholesterol increases the lipid bilayer permeability in the gel phase and decreases it in the fluid phase.

9. The Tc of phospholipids depends on the following: length of the acyl chain in the lipid degree of saturation of the hydrocarbon chains in the lipid ( Saturated F.a Stability of phospholipid) ionic strength of the suspension medium type of the polar head group

10. Types of Liposomes Based on Structure The liposome size can vary from very small (0.025 μm ) to large (2.5 μm ) vesicles. Moreover, liposomes may have one or bilayer membranes. The vesicle size is an acute parameter in determining the circulation half-life of liposomes, and both size and number of bilayers affect the amount of drug encapsulation in the liposomes . Unilamellar liposome ( one phospholipid bilayer) Small Unilamellar liposome (SUV) (10-100 nm) Large Unilamellar liposome (LUV) ( >100nm) Multilamellar Liposome ( more than one Phospholipid bilayer ) (onion- like structure)(MLV) >500nm . Multivesicular Liposome (Honey Comb like) (MVV) >1µm . Giant Univesicular Liposome(GUV ) >1-100 µm

11. Types of liposomes according to composition Conventional liposomes 1- They consist of only phospholipid bilayer(s) with /without cholesterol . 2- they tend to aggregate or fuse with each other resulting in immature release of liposomal payload overtime . 3-Rapidely cleared from blood circulation via phagocytosis , so it applied in anti-microbial agents , vaccination and antigen delivery

12. pH – sensitive liposomes 1- they consist of pH- sensitive phospholipid (ex: DOPE). 2- Used in targeted drug delivery specially in malignant tumors treatment by intracellular drug delivery mechanism ( they have ability to transfer their content into the cell interior through fusion or destabilization of endosomes, which has weakly acidic media)

13. Immuno-liposomes 1- they generated by coupling of antibodies to the liposomal surface and allow for an active tissue targeting through binding to tumor cell specific receptors . Mechanism of controlled drug release of immunoliposomes

14. Long circulating liposomes (PEGylated liposomes) 1- they contain polyethylene glycol (PEG)on the surface with/without specific ligands for longer circulation time.

15. Thin film hydration method ( Bangham method) MLV liposomes SUV liposomes

16. Solvent injection method

17. Detergent Removal method

18. Microfluidic Channel method

19. Mozafari method https://www.researchgate.net/post/In_the_first_stage_of_Mozafari_method_for_nanoliposome_preparation_what_should_be_done_to_prepare_nanoliposomes_from_water-insoluble_materials

20. pH jumping method