Large unilamellar lipid vesicles for use in therapeutic and diagnostic medicine

Large unilamellar lipid vesicles are prepared by a detergent dialysis procedure using beta-D-octylglucoside as the detergent. This procedure is nondenaturing and allows for the encapsulation of sensitive biological molecules. Vesicles prepared with the composition of 2 mol phosphatidylcholine and 1 mol cholesterol have a mean diameter of 200 nm and allow for the encapsulation of 150 molecules of alkaline phosphatase per vesicle without loss of activity. Stability studies show that less than 4 per cent of the original enzyme leaks from the vesicles over a 250 day period upon storage at 4 degrees C. A mechanistic model for vesicle formation is described to provide a clear understanding of the events occurring during the encapsulation stages.