Labile Incorporation of Cholesterol-Terminated Poly(acrylic acid) for the Facile Surface-Modification of Lipid Vesicles

An amphiphilic cholesterol-terminated poly[acrylic acid] (Chol-PAA) that can be self-aggregated into nanoscale micelles in aqueous media has been prepared via nitroxide-mediated radical polymerization for the facile postformation modification of lipid vesicles. By varying the amount of Chol-PAA addition, the incorporation of Chol-PAA on the liposome templates was verified with zeta potential while the dynamic light scattering measurements revealed the polymer length of Chol-PAA dictated the hydrodynamic diameter of the resulting polymer-grafted vesicles (PGVs). The membrane incorporation process of Chol-PAA was monitored through the fluorescence resonance energy transfer (FRET) study, which showed the relatively labile incorporation property of Chol-PAA, compared to the cholesterol-free PAA and the native cholesterol. Additionally, the postmodification of liposomes with such labile Chol-PAA exhibited a negligible leakage of calcein payloads, which can be attributed to the partial modification of the external membrane. These results indicated that our Chol-PAA can be exploited for the facile construction of functional polymer-decorated liposomal delivery systems.