Method of loading preformed liposomes using ethanol

Abstract

This invention provides methods of loading preformed liposomes by transmembrane permeation induced by alcohols. Solutes loaded into liposomes by this ethanol mediated process include both small nonpolar molecules and larger species, such as proteins and carbohydrates.

Description

[0001] This invention relates to the field of liposomes. More particularly this invention relates to the field of loading liposomes or releasing solutes from liposomes by transmembrane permeation.[0002] Liposomes are completely closed lipid bilayer membranes containing an entrapped aqueous volume. Liposomes may be unilamellar vesicles (possessing a single membrane bilayer) or multilamellar vesicles (onion-like structures characterized by multiple membrane bilayers, each separated from the next by an aqueous layer). The bilayer is composed of two lipid monolayers having a hydrophobic "tail" region and a hydrophilic "head" region. The structure of the membrane bilayer is such that the hydrophobic (non-polar) "tails" of the lipid monolayers orient toward the center of the bilayer while the hydrophilic (polar) "heads" orient towards the aqueous phase.[0003] A variety of liposome types are known and include multilamellar vesicles (MLV's), single unilamellar vesicles (SUV's), large unilam...

AI Technical Summary

Benefits of technology

[0024] combining an aqueous solution having liposomes dispersed therein with the solute and an organic solvent which increases the membrane permeability of the liposomes to the solute, whereby the solute enters the liposome by transmembrane permeation, and

[0025] diluting the concentration of the organic solvent thereby decreasing the membrane permeability of the liposome to the solute and trapping the solute in the liposome to provide a liposome loaded with solute.

[0029] Another advantage of the present invention is that the liposome size remains substantially unaltered during the membrane permeation process. The method is of particular value for increasing membrane permeation to and loading solutes with a low net charge or low charge to mass ratio.

Problems solved by technology

Another example occurs when the solute is trapped by a binding substance, such as an antibody, which thereby reduces the effective concentration of the free solute, thus preserving the concentration gradient of free solute between the two sides of the membrane.

However, this process is not of practical use with respect to loading solutes (such as drugs) into preformed vesicles unless the permeability barrier can be restored rapidly enough to effectively trap solute.

Generally, highly negatively charged species such as polynucleotides do not cross liposomal membranes permeabilized by the solvent technique disclosed herein and are loaded with low levels of efficiency.

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