title: New insights into self-organization of a model lipid mixture and quantification of its adsorption on spherical polymer particles.
abstract: The adsorption of lipids onto spherical polymer colloids led to original assemblies presenting structural characteristics adjustable with the lipid formulation. The model system selected for this work involved sulfate-charged poly(styrene) submicrometer particles and zwitterionic/cationic lipid mixtures composed of 1,2-dipalmitoyl-sn-glycero-3-phosphocholine (DPPC) and 1,2-dipalmitoyl-3-trimethylammonium-propane (DPTAP). According to the theoretical packing parameter calculations and whatever the DPPC/DPTAP ratio, the two lipids self-assembled in aqueous media to spontaneously form vesicles. A phase transition investigation of these DPPC/DPTAP vesicles using differential scanning calorimetry revealed particular thermotropic behaviors, especially for the equimolar formulation where very strong interactions occurred between DPPC and DPTAP. Furthermore, the coating of the lipids around particles was monitored versus DPPC/DPTAP ratio by means of numerous appropriate techniques. First, a thermogravimetric analysis, providing decomposition profiles of lipid/polymer particle assemblies with temperature, was atypically carried out for such nanostructures. Then, 1H NMR spectroscopy enabled the exact DPPC/DPTAP molar ratios adsorbed on particles to be determined by differentiating both lipids. Subsequently, it also pointed out the major role of electrostatic interactions as driving forces in the assembly elaboration process. In addition to these findings, quantitative information has been collected and correlated with chemical lipid assays and permitted the statement of a lipid bilayer coverage for the assemblies prepared in water, in agreement with quasi-elastic light scattering data.
authors.affiliation: UMR 2714 CNRS/bioMérieux, Systèmes Macromoléculaires et Physiopathologie Humaine, ENSL, 46, allée d'Italie, 69364 Lyon Cedex 07, France.
authors.forename: Anne-Lise
authors.initials: AL
authors.lastname: Troutier
authors.forename: Laurent
authors.initials: L
authors.lastname: Véron
authors.forename: Thierry
authors.initials: T
authors.lastname: Delair
authors.forename: Christian
authors.initials: C
authors.lastname: Pichot
authors.forename: Catherine
authors.initials: C
authors.lastname: Ladavière
mesh_terms: D015060:1,2-Dipalmitoylphosphatidylcholine / Q000737:chemistry*; D000327:Adsorption; D002152:Calorimetry, Differential Scanning; D003102:Colloids / Q000737:chemistry; D008027:Light; D008051:Lipid Bilayers; D008055:Lipids / Q000737:chemistry*; D009682:Magnetic Resonance Spectroscopy; D011108:Polymers / Q000737:chemistry*; D011407:Propane / Q000031:analogs & derivatives* / Q000737:chemistry*; D000644:Quaternary Ammonium Compounds / Q000737:chemistry*; D012542:Scattering, Radiation; D019032:Spectrometry, Mass, Matrix-Assisted Laser Desorption-Ionization; D055672:Static Electricity; D013499:Surface Properties; D013818:Thermogravimetry
chemical_list: C519974:1,2-dipalmitoyl-3-trimethylammonium-propane; D003102:Colloids; D008051:Lipid Bilayers; D008055:Lipids; D011108:Polymers; D000644:Quaternary Ammonium Compounds; D015060:1,2-Dipalmitoylphosphatidylcholine; D011407:Propane