An Ionic Polymer Bead-supported Lipid System Using Naturally Occurring Phospholipids

Abstract

Spherically supported bilayer membranes on cationic polymer beads were prepared from naturally occurring phospholipids [phosphatidylcholine (PC) and phosphatidylserine (PS)]. The amount of phospholipids bound to the cationic polymer beads from the liposomal suspensions of various lipid compositions increased with increases in anionic PS.Confocal fluorescence microscopic observations with a fluorescence membrane probe indicated that the phospholipid molecules in the phospholipid-bead complexes were along the surface of the beads.Negatively charged trypan blue dye was preferably bound to the phospholipid-free beads by electrostatic attractive interaction, but was excluded from the phospholipidbead complexes due to the bilayer membrane structure formed on the beads. This method could provide a better mimetic of biological membranes in comparison to physically unstable conventional liposomes.KEY WORDS: bilayer membrane, confocal fluorescence microscopy, phospholipid, polymer bead 3

Fluorescence microscopic characterization of ionic polymer bead-supported phospholipid bilayer membrane systems

“…In this study, bilayer membranes from the mixtures of PS and PC were reconstituted on a cationic organic polymer bead SA11A by a previously reported procedure [16,18]. During this preparation process, the electrostatic attractive forces between the anionic head group of the PS molecules and the fixed ammonium groups on the SA11A bead were thought to be responsible for the adhesion of the phospholipid vesicles onto the beads and the subsequent aggregation, rupture and fusion of the vesicles.…”

“…Recently, we reported a novel methodology for the preparation of SLM systems on ionic polymer beads in the range from 10 to 500 μm in diameter [16][17][18][19]; the electrostatic attractive forces between ionic lipids and the oppositely charged organic polymer beads appear to promote the formation and stabilization of the lipid bilayer membranes formed on the beads (Fig. 1).…”

Improved membrane fluidity of ionic polysaccharide bead-supported phospholipid bilayer membrane systems

“…The PS/PC-Q Sepharose complexes were prepared by a previously reported similar procedure [20,22]; the small unilamellar vesicle suspensions from phosphatidylcholine (PC) and phosphatidylserine (PS) were mixed with the Q Sepharose beads at a temperature in which the PC and PS are in lamella states. By using this methodology, we expected the 8 adhesion of the liposomes onto the surface of the Q Sepharose beads by electrostatic attractive forces, and subsequent liposomal membrane fusion and restructuring into the continuous phospholipid bilayer membrane structure.…”

“…We have already reported a novel methodology for the preparation of SLM systems on ionic polymer beads in the range from 10 to 500 μm in diameter [20][21][22][23]; the electrostatic attractive forces between ionic lipids and the oppositely charged organic polymer beads appear to promote the formation and stabilization of lipid bilayer membranes formed on the beads. So far, we have used hydrophobic polystyrene-based cationic spherical polymer beads as the supporting material for the preparation of the SLM systems.…”

One-step direct reconstitution of biomembranes onto cationic organic polymer bead supports

“…Recently, we developed a novel methodology for the preparation of an ionic polymer bead-supported lipid system, in which the electrostatic attractive interactions between the lipids and ionic polymer beads serve as "molecular glue" to immobilize the lipid bilayer membranes on the beads [18,19]. We successfully applied the ionic surface character of the system prepared with an artificial anionic lipid as a stationary phase for ion-exchange chromatography, in which the binding of the anionic lipids to the cationic surface of the polymer beads appeared to lend stability to the supported bilayer structure [20].…”