Liposomes - Formulation strategies.pptx

Liposomes: Formulation strategies

1. Liposomes: Formulation strategies Name: Ishika Choudhary M.Pharma

2. Introduction to Liposomes Definition : Liposomes are spherical vesicles with one or more lipid bilayers, used to deliver drugs or therapeutic agents. Structure : Comprised of a phospholipid bilayer with an aqueous core. Types : Unilamellar (ULV), Multilamellar (MLV), and Oligolamellar vesicles. Applications : Drug delivery, gene therapy, and cosmetic formulations.

3. Advantages of Liposomes Enhanced Drug Delivery : Liposomes can encapsulate both hydrophilic and lipophilic drugs. Targeted Delivery : Liposomes can be functionalized to target specific cells or tissues. Reduced Toxicity : They can reduce the toxicity of drugs by encapsulating them in a lipid bilayer. Controlled Release : Liposomes allow for controlled or sustained release of encapsulated drugs.

4. Liposome Formulation Strategies Choice of Lipid : Phosphatidylcholine, sphingomyelin, and cholesterol. Impact of lipid composition on liposome stability and drug release. Encapsulation Methods : Thin Film Hydration Method : A lipid film is formed and hydrated to form liposomes. Reverse Phase Evaporation : Lipids are dissolved in organic solvents and emulsified in aqueous solutions. Freeze-Thaw Method : Repeated freezing and thawing cycles to create liposomes. Hydration Method : Direct hydration of lipid films in water or buffer to form liposomes.

5. Liposome Composition Lipids : Phospholipids (e.g., DPPC, DSPC), cholesterol, and other lipids. Additives : Polyethylene glycol (PEG) for PEGylation to enhance circulation time. Stabilizers : To protect liposomes from degradation or fusion. Drug Molecules : Hydrophilic or lipophilic drugs encapsulated within the liposome.

6. Methods for Liposome Preparation Solvent Evaporation Method : Lipid dissolved in organic solvent, then evaporated under reduced pressure to form a thin film. Hydration of the film to form liposomes. Reverse-Phase Evaporation : Formation of an emulsion followed by solvent evaporation. Extrusion Technique : Liposomes pass through filters to create uniform sizes. Sonication : Ultrasound used to break down lipid aggregates into smaller liposomes.

7. Types of Liposomes Unilamellar Vesicles (ULV) : Single lipid bilayer. Multilamellar Vesicles (MLV) : Multiple lipid bilayers with alternating aqueous layers. Small Unilamellar Vesicles (SUV) : Smaller, single-layer vesicles. Large Unilamellar Vesicles (LUV) : Larger single-layer vesicles.

8. Surface Modification of Liposomes PEGylation : The process of attaching polyethylene glycol (PEG) to the liposome surface to increase stability, reduce immunogenicity, and improve circulation time. Targeted Liposomes : Surface modification with ligands (e.g., antibodies, peptides) to target specific receptors on cells ( tumor cells, for example).

9. Liposome Drug Loading Techniques Passive Loading : Drugs are incorporated during the formation of liposomes. Active Loading : A drug is loaded post-liposome formation by using methods like pH gradient or ammonium sulfate gradient to increase encapsulation efficiency. Remote Loading : A drug is added to liposomes that have a pre-established internal gradient, improving drug encapsulation and release profiles.

10. Factors Affecting Liposome Formulation Lipid Composition : The types of lipids used affect the stability and size of liposomes. Drug Properties : The solubility, charge, and size of the drug influence its encapsulation. Method of Preparation : Different techniques influence the size, charge, and drug encapsulation efficiency of liposomes. Sterilization Methods : Autoclaving or filtration techniques impact liposome stability.

11. Characterization of Liposomes Size and Distribution : Dynamic Light Scattering (DLS) Electron Microscopy (EM) Zeta Potential : Determines the stability of liposomes based on surface charge. Encapsulation Efficiency : Determining how much of the drug is successfully encapsulated inside the liposomes. Leakage Studies : Measures how much of the encapsulated drug leaks from liposomes over time.

12. Challenges in Liposome Formulation Instability : Liposomes can be unstable, especially in the presence of serum proteins. Scalability : Difficulty in scaling up liposome production from lab to industrial scale. Drug Release Control : Achieving consistent, controlled release of encapsulated drugs is challenging. Toxicity : Some liposome formulations may cause toxicity or immunogenic reactions.

13. Applications of Liposomes Cancer Therapy : Targeted liposomes can deliver chemotherapeutic agents to tumor sites. Gene Therapy : Liposomes as vehicles for delivering genetic material. Vaccine Delivery : Liposomes as adjuvants to improve immune responses. Cosmetics : Liposomes in cosmetic formulations for skin delivery.

14. Recent Advances in Liposome Formulation Liposomes for RNA Delivery : Advances in mRNA vaccines (e.g., COVID-19 vaccines) using liposomal delivery systems. Smart Liposomes : Liposomes that respond to stimuli (e.g., pH, temperature) for controlled release. Nanoliposomes : Smaller liposomes for more precise targeting and enhanced stability.

15. Conclusion Liposomes are versatile and effective drug delivery systems. Formulation strategies must be carefully chosen based on the drug properties, application, and targeted delivery goals. Despite challenges, liposomes offer numerous advantages, particularly in targeted drug delivery and reducing toxicity.

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