title: Characterization of phosphatidylcholine/polyethylene glycol-lipid aggregates and their use as coatings and carriers in capillary electrophoresis.
abstract: PEG-stabilized lipid aggregates are a promising new class of model membranes in biotechnical and pharmaceutical applications. CE techniques, field-flow fractionation, light scattering, quartz crystal microbalance (QCM), and microscopic techniques were used to study aggregates composed of 1-palmitoyl-2-oleyl-sn-glycero-phosphatidylcholine (POPC) and PEG-lipid conjugates. The PEG-lipids, with PEG molar masses of 1000, 2000, and 3000, were 1,2-diacyl-sn-glycero-3-phosphoethanolamine-N-[methoxy-(PEG)] derivatives with either dimyristoyl (DM, 14:0) or distearoyl (DS, 18:0) acyl groups. The 80/20 mol% POPC/PEG-lipid dispersions in HEPES at pH 7.4 were extruded through 100 nm size membranes. Asymmetrical flow field-flow fractionation (AsFlFFF), photon correlation spectroscopy (PCS), and dynamic light scattering (DLS) were used to determine the sizes of POPC and the PEGylated aggregates. All methods demonstrated that the DSPEG-lipid sterically stabilized aggregates were smaller in size than pure POPC vesicles. The zeta potentials of the aggregates were measured and showed an increase from -19 mV for pure POPC to -4 mV for the POPC/DSPEG3000 aggregates. Atomic force microscopy (AFM), electron cryo-microscopy (EM), and multifrequency QCM studies were made to achieve information about the PEGylated coatings on silica. Lipid aggregates with different POPC/DSPEG3000-lipid ratios were applied as capillary coating material, and the 80/20 mol% composition was found to give the most suppressed and stable EOFs. Mixtures of low-molar-mass drugs and FITC-labeled amino acids were separated with the PEGylated aggregates as carriers (EKC) or as coating material (CEC). Detection was made by UV and LIF.
authors.affiliation: Laboratory of Analytical Chemistry, Department of Chemistry, University of Helsinki, Helsinki, Finland.
authors.forename: Maria V
authors.initials: MV
authors.lastname: Lindén
authors.forename: Kristoffer
authors.initials: K
authors.lastname: Meinander
authors.forename: Anne
authors.initials: A
authors.lastname: Helle
authors.forename: Gebrenegus
authors.initials: G
authors.lastname: Yohannes
authors.forename: Marja-Liisa
authors.initials: ML
authors.lastname: Riekkola
authors.forename: Sarah J
authors.initials: SJ
authors.lastname: Butcher
authors.forename: Tapani
authors.initials: T
authors.lastname: Viitala
authors.forename: Susanne K
authors.initials: SK
authors.lastname: Wiedmer
mesh_terms: D000596:Amino Acids / Q000032:analysis; D020285:Cryoelectron Microscopy / Q000379:methods; D019075:Electrophoresis, Capillary / Q000379:methods*; D008081:Liposomes / Q000737:chemistry*; D008823:Micelles; D018625:Microscopy, Atomic Force / Q000379:methods; D010713:Phosphatidylcholines / Q000737:chemistry*; D011092:Polyethylene Glycols / Q000737:chemistry*
chemical_list: D000596:Amino Acids; D008081:Liposomes; D008823:Micelles; D010713:Phosphatidylcholines; D011092:Polyethylene Glycols; C028694:1-palmitoyl-2-oleoylphosphatidylcholine