Liposomes and Drug Delivery Lecture Notes

A set of vocabulary flashcards covering the definitions, types, mechanisms of action, and biological functionality of liposomes as drug delivery systems.

Liposomes

Spherical self-closed structures, composed of curved lipid bilayers, which enclose an aqueous core and surrounding solvent into their interior.

Amphiphiles

Molecules that possess both hydrophilicity (interacts with water) and hydrophobicity (avoids water) and tend to aggregate spontaneously to hide hydrophobic regions.

Micellar structures

Structures formed in an aqueous environment by amphiphilic lipids with 1 alkyl chain.

Lamellar structures

Bilayer structures formed in an aqueous environment by amphiphilic lipids with 2 alkyl chains.

Cylindrical shape (amphiphiles)

A geometry where polar and non-polar regions are equal, leading to the formation of a bilayer or lamellar phase.

Cone shape (amphiphiles)

A geometry that results in the formation of polymeric micelles during self-assembly.

SUVs

Small unilamellar vesicles with a single bilayer and a size range between $25-100\,nm$.

LUVs

Large unilamellar vesicles with a single bilayer and a size range between $0.1-1\,mm$.

MLVs

Multilamellar vesicles containing many bilayers with a size range between $0.1-20\,mm$.

OLVs

Oligolamellar vesicles consisting of only 2-3 bilayers.

Multivesicular liposomes

Structures characterized by having multi vesicles contained within one large vesicle.

Adsorption (liposome-cell interaction)

A mechanism where liposomes attach to the cell membrane, leading to the extracellular release of the entrapped drug.

Lipid exchange

An interaction where the lipophilic components of the liposome bilayers are transferred to the cell membrane, releasing the drug into the cytoplasm.

Endocytosis

A common interaction mechanism where the entire liposome is engulfed by the cell and digested by lysosomes to release the drug.

Fusion

A mechanism where the liposome merges with the cell membrane to release its content, often utilized in gene therapy.

Reticuloendothelial systems (RES)

The immune system component, consisting of macrophages in the liver, spleen, and lungs, responsible for the rapid clearance of liposomes from circulation.

Cationic liposomes

Positively charged vesicles typically used for gene therapy to enhance ionic interaction and adsorption on the cell surface.

Immunoliposomes

Liposomes with antibodies attached to their surface to improve target ability and provide targeted drug delivery.

Stealth Liposomes (SSL)

Sterically-stabilised liposomes formulated from PEG to produce hydrophilic surfaces that evade immune detection and extend circulation time.

PEG

Polyethylene glycol; used to coat liposomes to make them more hydrophilic and harder for macrophages to recognize.

Doxorubicin HCl

A drug encapsulated in Stealth liposomes used specifically for treating Kaposi’s sarcoma and other cancers.

EPR effect

Enhanced permeability and retention effect; a phenomenon where liposomes enter and are retained in tumours due to impaired lymphatic drainage.