title: Interactions between phospholipids and titanium dioxide particles.
abstract: A systematic study was carried out on monolayer films and lipid vesicles to elucidate the interactions between membrane lipids and commercial particles of titanium dioxide TiO2 (TiO2-P25). Pressure-area isotherms of lipids at various pH values were recorded on a Langmuir trough with or without TiO2-P25 and NaCl in the subphase. Electrophoretic mobilities of lipid vesicles and TiO2-P25 particles were measured to identify the pH range where attractive electrostatic interactions between lipids and TiO2-P25 could take place. The results show that (i) the surface of TiO2-P25 particles interacts only with some phospholipids, (ii) the driving forces are electrostatic and (iii) non-electrostatic interactions were also observed, depending on the molecular structure. More precisely, the phospholipids 1,2-dimyristoyl-sn-glycero-3-phosphate monosodium salt (DMPA), 1,2-dimyristoyl-sn-glycero-3-phospho-rac-1-glycerol (DMPG) and 1',3'-bis[1,2-dimyristoyl-sn-glycero-3-phospho]-sn-glycerol (TMCL) interacted strongly with the TiO2-P25 surface through electrostatic interactions, providing they were oppositely charged, i.e. for pH between 2 and 6.6. For TMCL and DMPG, interactions with the surface of TiO2-P25 in non-favourable electrostatic conditions, suggested another kind of binding, probably through the hydroxyl groups of the terminal glycerol. Weaker attractive interactions were demonstrated for 1,2-dimyristoyl-sn-glycero-3-phospho-l-serine (DMPS) and the synthetic lipid dihexadecyl phosphate (DHP). For DMPS, the carboxylate group is involved in the adsorption onto TiO2. The other membrane lipids such as 1,2-dimyristoyl-sn-glycero-3-phosphocholine (DMPC), 1,2-dimyristoyl-sn-glycero-3-phosphoethanolamine (DMPE) and sphingomyelin (SM) did not interact with TiO2-P25 regardless of pH.
authors.affiliation: Institut Matériaux Jean Rouxel IMN, UMR 6502, Univ Nantes, CNRS, F-44322 Nantes 3, France.
authors.forename: Quoc-Chon
authors.initials: QC
authors.lastname: Le
authors.affiliation: INRA, UR1268 Biopolymères Interactions Assemblages, F-44300 Nantes, France. Electronic address: marie-helene.ropers@nantes.inra.fr.
authors.forename: Marie-Hélène
authors.initials: MH
authors.lastname: Ropers
authors.affiliation: Institut Matériaux Jean Rouxel IMN, UMR 6502, Univ Nantes, CNRS, F-44322 Nantes 3, France.
authors.forename: Hélène
authors.initials: H
authors.lastname: Terrisse
authors.affiliation: Institut Matériaux Jean Rouxel IMN, UMR 6502, Univ Nantes, CNRS, F-44322 Nantes 3, France.
authors.forename: Bernard
authors.initials: B
authors.lastname: Humbert
mesh_terms: D006863:Hydrogen-Ion Concentration; D010743:Phospholipids / Q000737:chemistry*; D055672:Static Electricity; D014025:Titanium / Q000737:chemistry*
chemical_list: D010743:Phospholipids; C009495:titanium dioxide; D014025:Titanium
keywords: Langmuir film; Phospholipid; Pressure-area isotherm; Surface charge; Titanium dioxide; Zeta potential