Surface Modification of Porous Vesicles via Hydrolysis

The surfaces of skeletonized vesicles (or vesicles with holes) are hydrophilic. If the hydrophilic surfaces are chemically modified to have a reasonable compatibility with organic solvents, the application of vesicular colloids can be expanded. In this study, 1,2-dipalmitoyl-sn-glycro-3-phosphocholine (DPPC) and N,N-bis[10-(4-vinylbenzyloxy)decanoylaminoethyl]-N,N-dimethylammonium chloride (BDAC) were employed as a nonpolymerizable lipid and polymerizable surfactant, respectively. Divinylbenzene (DVB) was used as a cross-linking agent in the polymerization of the vesicles. Multilamellar vesicles composed of BDAC and DPPC with embedded DVB in a 3:2:3 molar ratio underwent efficient radical polymerization. DPPC was removed from the cross-linked vesicles using Triton X-100 (skeletonization). The headgroup of BDAC was removed by hydrolysis in an acidic condition. The surface of the polymerized vesicles looked very smooth, but the skeletonized vesicles looked pretty rough and showed only small interstices or holes. the DSC experiment showed that DPPC domains were widely distributed in size after polymerization. The hydrolyzed vesicle surface looked wrinkled, probably due to the enhanced fluidity of the alkyl chains. The hydrolyzed vesicles were precipitated or aggregated in many individual organic solvents but were well dispersed in a 1.0 M NaOH water/methanol (1/1) solution.