Large-Scale Production of Liposomes of Defined size by a New Continuous High Pressure Extrusion Device

Abstract

A new continuous high pressure extrusion apparatus for the generation of liposomes was designed and tested in the present study. The extruder, which basically consists of an open supply vessel and a high pressure filter holder mounted on a gas-driven pump exhibited superior abilities compared to currently available, discontinuous extrusion devices. Due to continuous flows up to 500 ml/min (filter diameter 47 mm), large batches on a liter scale could be extruded in one step. The maximum pressure of 10.5 MPa employed here, enabled the rapid passage of liposomal preparations with various lipid compositions at lipid concentrations as high as 400 mg/g through polycarbonate membranes without any clogging of the system. Employing final pore sizes between 5.0 and 0.03 μm, the mean vesicle diameter of liposomal preparations could be varied from 400 to 60 nm. Surprisingly high encapsulation efficiencies of two water-soluble contrast agents, iopromide and Gd-DTPA, which we used as model substances, were obtained for...