Hemp Therapies Wiki / Liposomal Delivery Systems

Liposome Structure and Types

Liposomes are generally described as ranging from about 25 nanometers to several micrometers in overall diameter, depending on production method and intended use, and they come in several distinct structural types.

Structural Types

A “unilamellar” liposome, also called a single lamellar vesicle, has one continuous phospholipid bilayer enclosing a single aqueous compartment. Unilamellar vesicles are further classified as small unilamellar vesicles (SUV) or large unilamellar vesicles (LUV) based on overall particle diameter. A “multilamellar” liposome (MLV) contains several concentric phospholipid bilayers, resembling the layered cross-section of an onion. A “multivesicular vesicle” (MVV) contains numerous smaller unilamellar vesicles held inside one larger outer vesicle.

How Structure Affects Encapsulation

Encapsulation capacity for water-soluble compounds tends to increase with a liposome’s internal aqueous volume, while additional bilayer count in a multilamellar structure can reduce hydrophilic-compound loading per particle. In a liposome bilayer, the hydrophobic tails of the phospholipid molecules orient toward the center of the membrane, while the hydrophilic heads orient toward both the internal aqueous core and the external watery environment.

Summary

A liposome’s structural type — unilamellar, multilamellar, or multivesicular — directly affects how much of a water-soluble ingredient it can carry, making structure type one of the key physical attributes distinguishing one liposomal formulation from another.