Lipid vesicles (or liposomes) are considered model membranes and are used to understand natural cell membranes and encapsulate and target the delivery of drugs, flavors and DNA. Recently, there has been considerable interest in another group of amphiphilic materials; amphiphilic block co-polymers that self-assemble into vesicles termed polymersomes. Polymersomes have several potential advantages over liposomes, including increased strength and decreased permeability. Vesicle formation procedures applicable to lipid vesicles have been used to form polymeric vesicles. These methods include rehdyration, electroformation and solvent injection. However, these methods generally yield a broad spectrum of vesicle sizes. The ability to obtain a unimodal vesicle size can be of great significance in applications as well as in fundamental property studies. The current bulk methods for vesicle formation also create local environments with variable characteristics that may be difficult to control and lead to inhomegenieties. Production of vesicles in a uniform microenvironment enables greater control over vesicle characteristics such as size and encapsulation efficiency. In a microfluidics device, flow rates can be controlled to create and maintain interfaces between different flow streams. We have developed a microfluidic device for the formation of monodisperse polymersomes from amphiphilic block copolymers. The polymers consist of hydrophobic poly(butadiene) and hydrophilic poly(acrylic acid). The microfluidic device consists of concentric capillaries in which an inner fluid is surrounded by a polymer solution. This stream is then passed through a viscous interface and breaks up to form monodisperse drops, which, upon dialysis of the organic phase, results in polymersomes.
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