Rapid Access to Giant Unilamellar Liposomes with Upper Size Control: Membrane-Gated, Gel-Assisted Lipid Hydration

Combining gel-assisted lipid hydration with membrane-based lipid extrusion, we demonstrate here a general procedure for rapid preparation of giant unilamellar liposomes with upper size control. Featured in this procedure are planar lipid stacks deposited on poly(vinyl alcohol) gel, which are further laminated atop with microporous polycarbonate membranes. Control of liposome size is thus realized through the uniform-sized pores of the latter, which provide the only access for the underlying lipids to enter the main aqueous phase upon hydration. Production of both single-phased and biphasic (Janus) liposomes using several commonly employed model lipids, including 1,2-dipalmitoyl-sn-glycero-3-phosphocholine (DPPC), 1,2-dioleoyl-sn-glycero-3-phosphocholine (DOPC), 1-palmitoyl-2-oleoyl-glycero-3-phosphocholine (POPC) and cholesterol, is presented. The size distribution, yield and lamellarity of these liposome products are characterized and analyzed in detail by confocal fluorescence microscopy. This procedure thus offers a simple and fast alternative route to giant unilamellar liposomes with upper size control.