title: Composition and properties of complexes between spherical polycationic brushes and anionic liposomes.
abstract: A spherical polycationic brush (SPB) is made by graft-polymerizing a cationic monomer onto the surface of a 100 nm polystyrene bead. It is possible to adsorb anionic liposomes (40-60 nm diameter) onto the SPBs while maintaining the liposome integrity. The liposomes were constructed with phosphatidyl choline (PC) admixed with 0.05-0.4 mol fraction of an dianionic lipid, cardiolipin (CL(2-)). As shown by electrophoretic mobility measurements, SPB-to-liposome complexation leads to a conversion from the initial positive charge of the copolymer to a negative charge. The higher the CL(2-) content of the liposomes, the lower the concentration needed for charge neutralization. Dynamic light scattering (DLS) revealed that multicomplex aggregates are formed with a maximum size at the SPB/liposome charge-equivalence point. Experiments with fluorescent-labeled liposomes show that at low CL(2-) content about 80 liposomes are adsorbed per SPB. As the mole fraction of CL(2-) increases from 0.05 to 0.4, fewer liposomes adsorb owing to electrostatic repulsion among neighboring liposomes. The effect of added NaCl also depends upon the CL(2-) content. With 0.05 mol fraction CL(2-), the SPB/liposome complex dissociates into its components at 0.15 M NaCl. With a mole fraction of >0.1, complexes fail to dissociate even at 1.2 M NaCl. Additional information about the SPB/liposome morphology was obtained from cryo-TEM. For example, cryo-TEM data confirm liposome integrity upon complexation, a behavior that contrasts with the liposome destruction as found with adsorption to many other types of surfaces.
authors.affiliation: Department of Chemistry, MV Lomonosov Moscow State University, Moscow, Russian Federation. sybatchin@mail.ru
authors.forename: Andrey V
authors.initials: AV
authors.lastname: Sybachin
authors.forename: Olga V
authors.initials: OV
authors.lastname: Zaborova
authors.forename: Matthias
authors.initials: M
authors.lastname: Ballauff
authors.forename: Ellina
authors.initials: E
authors.lastname: Kesselman
authors.forename: Judith
authors.initials: J
authors.lastname: Schmidt
authors.forename: Yeshayahu
authors.initials: Y
authors.lastname: Talmon
authors.forename: Fredric M
authors.initials: FM
authors.lastname: Menger
authors.forename: Alexander A
authors.initials: AA
authors.lastname: Yaroslavov
mesh_terms: D000838:Anions / Q000737:chemistry; D002308:Cardiolipins / Q000737:chemistry; D002412:Cations; D020285:Cryoelectron Microscopy; D005456:Fluorescent Dyes / Q000737:chemistry; D008081:Liposomes / Q000737:chemistry* / Q000648:ultrastructure; D010713:Phosphatidylcholines / Q000737:chemistry; D011137:Polystyrenes / Q000737:chemistry; D012542:Scattering, Radiation; D012965:Sodium Chloride / Q000737:chemistry; D055672:Static Electricity
chemical_list: D000838:Anions; D002308:Cardiolipins; D002412:Cations; D005456:Fluorescent Dyes; D008081:Liposomes; D010713:Phosphatidylcholines; D011137:Polystyrenes; D012965:Sodium Chloride