Syntheses and vesicle-forming characteristics of nonionic polymeric amphiphiles

Abstract

Since the charged bilayer membranes are prone to precipitate at high ionic strength, the synthetic bilayer membranes without any ionic charges are of interest from the view point of searching for the membrane which are stable in the wider range of salt concentration. We have synthesized polymerizable nonionic amphiphiles which contain sugar rings, glycols, acryamide and/or methacryamide moieties in the hydrophilic polar heads and two long alkyl chains in hydrophobic tails. The nonionic amphiphiles containing sugar moiety could not be dispersed in aqueous solution, but those prepared from tetraethylene glycol, acryamide and/or methacryamide were hydrophilic enough to become dispersable in aqueous solution. We have also synthesized the copolymeric nonionic amphiphiles containing cholesterol. Several factors (types of hydrophilic comonomers, molecular weight, and composition ratio) which influence the vesicleforming characteristrics of copolymeric amphiphiles were investigated. In the search for the potential method to extract the free cholesterol from certain biological systems using our nonionic cholesterol-based vesicles, the extraction experiments were carried out using labeled monomeric $[^14C]$ cholesterol as a probe. The results indicated that the present system was found to be effective for the extraction of cholesterol in water by our cholesterol-based polymeric vesicles.