Video summary

Week 02: Lecture 09: Introduction on Lipid-based nanocarriers-I

Main summary

Key takeaways

Educational

Main ideas, concepts, and lessons

  • Course context / lecture focus

    • The lecturer (Dr. Satish Dawanapali) reviews earlier content on polymeric nanoparticulate drug delivery systems (polymeric nanoparticles, methods like solvent evaporation/emulsification/diffusion, nanoprecipitation, polymeric micelles, dendrimers, polymer–drug concepts).
    • Today’s topic: Lipid-based nanocarrier systems, beginning with liposomes.

  • Goal and learning roadmap

    • The lecture is structured to cover:
      1. Introduction to lipid nanocarriers
      2. Liposomes: definition/structure, advantages
      3. Classification of lipid nanocarriers
      4. Types of liposomes in formulations
      5. Preparation methods for liposomes

Classification of lipid-based nanocarriers (as presented)

  • Liposomes
  • Solid lipid nanoparticles
  • Nanostructured lipid carriers

What lipid nanoparticles are (briefly defined)

  • Lipid nanoparticles are lipid-based particles in a ~10–1,000 nm size range that can carry drugs or genetic material.

Why lipid nanocarriers are attractive

  • Growing interest beyond pharma/biotech into cosmaceuticals.
  • Key drivers mentioned:
    • Safety / non-toxic profile
    • FDA approval relevance for drug and vaccine delivery

Liposomes: definition and structure

  • Liposomes are spherical bilayer vesicles made of one or more phospholipid bilayers.
  • They mimic cell membrane structure (biomimetic carriers).
  • They can form via self-assembly when lipids are dispersed in an aqueous medium (e.g., with stirring/heating).

Internal/external compartment concept

Phospholipids have:

  • Hydrophilic heads
  • Hydrophobic tails

This enables loading different drug types within one carrier:

  • Hydrophilic drugs → encapsulated in the aqueous core
  • Hydrophobic drugs → accommodated in the hydrophobic bilayer interior

Surface and functional modifications

Liposomes can be modified to enhance performance, including:

  • Conjugation with polymers
  • Surface modification with monoclonal antibodies and ligands
  • Surface charge modification to influence interactions and uptake

These modifications support encapsulation of drugs, proteins, peptides, and targeting strategies.

Mode of action / fate in the body

After administration, liposomes can be taken up by cells through:

  • Endocytosis
  • Membrane fusion

Inside cells, vesicles may degrade due to intracellular pH, leading to release of the drug.

How liposomes increase half-life

  • Example strategy: PEGylation
    • Conjugating polyethylene glycol (PEG) on the liposome surface.
    • Benefits mentioned:
      • Inhibits opsonization
      • Bypasses the reticuloendothelial system (RES)
      • Helps extend circulation / half-life

Active targeting

  • Achieved by labeling liposomes with carbohydrates, antibodies, or other ligands, often using cleavable linkers.
  • Used for targeting specific cells (e.g., cancer therapy and infectious diseases).

Role of cholesterol in liposomes

Cholesterol is described as important for bilayer formation and stability, functioning as:

  • A packing agent between phospholipids
  • Increasing membrane integrity and stability
  • Regulating membrane fluidity
  • Decreasing permeability
  • Preventing leakage of encapsulated contents
  • Increasing membrane rigidity to control drug release/leakage

Liposome classification (detailed)

1) Classification by vesicle structure/layers (vesicle number of bilayers)

  • Unilamellar vesicles (single phospholipid bilayer)

    • Small unilamellar vesicles (SUV)
      • Size range: ~20–100 nm
    • Large unilamellar vesicles (LUV)
      • Size: >100 nm

  • Multilamellar vesicles (multiple bilayers)

    • Oligolamellar vesicles
      • Layers: ~5 bilayers (as stated)
      • Size described around ~0.1–1 micron (values in subtitles appear inconsistent, but “micron” scale is emphasized)
    • Multilamellar vesicles (onion-type)
      • Layers: ~5 to 20 bilayers
      • Visual description: onion-like
    • Multi-vesicular vesicles
      • Contain multiple compartments/vesicles within one vesicle

2) Types of liposomes (based on surface charge/modification)

  • Conventional liposomes

    • Tend to have negative surface charge due to phosphate groups.
    • Downside: repulsion with similarly negative cell membranes, leading to decreased cellular uptake.

  • Cationic liposomes

    • Developed by introducing amino groups.
    • Positive charge → higher cellular uptake.
    • Mentioned as having higher interaction persistence / longer interaction with cells (relative claim).

  • PEG-coupled (PEGylated) liposomes

    • Include PEG groups on the surface.
    • Aim: reduce RES/reticuloendothelial system uptake → improve half-life.

  • Immunoliposomes

    • Targeting strategy using monoclonal antibodies or ligands conjugated to liposomes.
    • Intended for specific targeting (e.g., anti-cancer and infectious disease applications).

Liposome preparation methods (detailed)

Overview: general preparation workflow

  1. Dissolve/disperse lipids in a suitable organic solvent (and include drug as needed).
  2. Remove the solvent by drying (e.g., evaporation) to form a thin film (noted on glass/RBF).
  3. Hydrate the thin film using water/aqueous solution to form vesicles.
  4. Apply agitation/disruption/homogenization to promote self-assembly and/or reduce size.
  5. Purify the resulting liposomes.
  6. Characterize/analyze the final formulation.

Drug loading concepts

  • Passive loading
    • Load the drug after preparation of blank liposomes.
  • Active loading
    • Load the drug during the preparation method (incorporation during formulation steps).

Specific methods referenced for producing liposomes

  • Thin film hydration method

    • Key logic:
      • Dissolve lipid in organic solvent.
      • If drug is water-soluble: dissolve it in the aqueous phase during hydration.
      • If drug is water-insoluble/lipophilic: disperse it in the organic phase.
      • Remove solvent to form a thin lipid film.
      • Hydrate with water/aqueous solution.
      • Use mixing/vortexing to form vesicles.
    • Notes on outcome and size:
      • Produces large multilamellar vesicles.
      • To reduce size: apply disruption techniques such as:
        • Sonication
        • Exclusion/extrusion (subtitles mention “excusion/excision”)

  • Hand shaking method

    • Similar to thin-film hydration, but uses hand shaking.
    • Optional: use a rotavapor with vacuum/nitrogen to remove remaining solvent/water.
    • Then re-disperse in water to form liposomal dispersion.

  • Ethanol/ether injection method

    • Dissolve lipids (and optionally surfactant) in ethanol/ether.
    • Inject into an aqueous phase.
    • Vesicles form; size reduction can be achieved via:
      • Sonication
      • High pressure homogenization / high shear homogenation
      • Ultrasonication

  • Mechanical dispersion method (general description tied to thin film + hydration + size reduction)

    • Dissolve drug and lipid in organic solvent, remove solvent/water to form film, hydrate to yield large particles.
    • Reduce particle size using sonication, extrusion, or homogenization to obtain smaller unilamellar vesicles.

Selection principle (stated)

Method selection depends on:

  • Nature of lipid
  • Nature of drug
  • Desired carrier type

Commercial examples mentioned

  • The lecture briefly references commercial liposome-based products available in the market.
  • Examples (representative categories) include:
    • Antifungals
    • Anti-cancer drugs
  • Therapeutic areas referenced:
    • Leukemia
    • Leishmaniasis
    • Infectious diseases
    • Cancer therapy
  • Specific product names and companies were mentioned, but are not reliably captured in the auto-subtitles.

Speakers / sources featured

  • Dr. Satish Dawanapali
    • Assistant Professor, Department of Pharmaceutical Science and Technology,
    • Institute of Chemical Technology Mumbai

Original video