Porous Vesicles Dispersible in Organic Solvents

Abstract

The porous vesicles reported so far have hydrophilic surfaces. If the surfaces are chemically modified to be compatible with common organic solvents, their application will be extended. 1,2-Bis[9-(4vinylbenzyloxycarbonyl)nonanoyl]-sn-glycero-3-phosphocholine (BNPC) was synthesized and used as a polymerizable surfactant for the present study. Vesicles composed of BNPC and cholesterol with embedded divinylbenzene were polymerized, followed by skeletonization (removal of cholesterol) and hydrolysis (cleavage of the ester bonds in BNPC unit). The resulting vesicles (250 nm) whose surfaces contain hydroxyl groups appeared to have holes with diameters up to several tens of nanometers. They were dispersed in water, methanol, tetrahydrofuran, and chloroform. The turbidity of the dispersions decreased as follows: water > methanol > tetrahydrofuran > chloroform. The dispersion in water remained turbid with some precipitates during storage, but those in methanol and tetrahydrofuran appeared to be clear with white precipitates. On the other hand, the transparent vesicle dispersion in chloroform did not form precipitates.

Highly Stable Polymerizable Vesicles in Anionic Surfactant/Ammonium Salt Mixtures in the Presence of Cross-linking Monomers for Convenient Preparation of Hollow Nanospheres

“…Polymerization reactions in spherically closed amphiphilic bilayers, − i.e., vesicles and liposomes, − are known to fix the vesicular structure to provide stabilized hollow colloidal nanoparticles. − A number of unsaturated phospholipids have been synthesized for stabilization of liposomes. , Polymerization of metastable vesicles, typically formed by the dispersion of bilayer phases of double-chained surfactants incorporating polymerizable groups, lock even the nonequilibrium vesicular structures into place, preventing them from reverting to more stable flat bilayers . A number of amphiphilic cross-linking monomers have been explored to circumvent the problem of intravesicular phase separation that could induce significant deformation of vesicles upon polymerization. − Divinylbenzene (DVB) is known to swell the vesicle bilayers of various double-chained surfactants to act as a simple cross-linking agent. , Polymerization of unilamellar vesicles, spontaneously formed by the mixing of single-chained cationic and anionic surfactants incorporating polymerizable groups, has also been reported . Incorporation of DVB into the hydrophobic bilayer of the spontaneous vesicles provide hollow spheres after polymerization.…”

“…16 A number of amphiphilic cross-linking monomers have been explored to circumvent the problem of intravesicular phase separation that could induce significant deformation of vesicles upon polymerization. [17][18][19] Divinylbenzene (DVB) is known to swell the vesicle bilayers of various double-chained surfactants to act as a simple cross-linking agent. 16,20 Polymerization of unilamellar vesicles, spontaneously formed by the mixing of single-chained cationic and anionic surfactants incorporating polymerizable groups, has also been reported.…”