Surface modification of vesicles with methylol urea

Abstract

Surface-modified vesicles were prepared using N-[3-(dimethylamino)propyl]-octadecanamide and stearic acid as bilayer-forming lipids, and N-methylol urea-dodecylamine conjugates (MU-DOA) as a surface modifier. The conjugation of MU to DOA was confirmed by FTIR spectra, MU-DOA was incorporated into the vesicles by co-homogenization of the lipids and MU-DOA, and the incorporated MU-DOA was then reacted with MU in aqueous bulk phase through a self-condensation reaction between the methylols under an acidic condition at 70degreesC. On a scanning electron microscope, the vesicles were spherical and multilamellar, and they exhibited thin polymer films on their surfaces, The incorporation of MU-DOA into the bilayer and the surface coating of the vesicles did not significantly influence the transition temperature of the vesicles. The absolute values of zeta potentials of the surface-modified vesicles were smaller than those of the unmodified vesicles, and the point of zero charge was shifted from ca. pH 9.5 to ca. pH 6.5 by the surface modification.