Preparation, stability, and in vitro performance of vesicles made with diblock copolymers

Vesicles made completely from diblock copolymers-polymersomes-can be stably prepared by a wide range of techniques common to liposomes. Processes such as film rehydration, sonication, and extrusion can generate many-micron gi ants as well as monodisperse, similar to 100 nm vesicles of PEO-PEE (polyet hyleneoxide-polyethylethylene) or PEG-PSD (polyethyleneoxide-polybutadiene) . These thick-walled vesicles of polymer can encapsulate macromolecules jus t as liposomes can but, unlike many pure liposome systems, these polymersom es exhibit no in-surface thermal transitions and a subpopulation even survi ve autoclaving. Suspension in blood plasma has no immediate ill-effect on v esicle stability, and neither adhesion nor stimulation of phagocytes are ap parent when giant polymersomes are held in direct, protracted contact. Prol iferating cells, in addition, are unaffected when cultured for an extended time with an excess of polymersomes. The effects are consistent with the st eric stabilization that PEG-lipid can impart to liposomes, but the present single-component polymersomes are far more stable mechanically and are not limited by PEG-driven micellization. The results potentiate a broad new cla ss of technologically useful, polymer-based vesicles. (C) 2001 John Wiley & Sons, Inc.