title: Surfactant dependent morphology of polymeric capsules of perfluorooctyl bromide: influence of polymer adsorption at the dichloromethane-water interface.
abstract: In a strategy to develop more stable ultrasound contrast agents (UCAs), we have designed a process to obtain nano/microcapsules with a single core of liquid perfluorocarbon within a biodegradable polymeric shell of homogeneous thickness. During the optimization of perfluorooctyl bromide (PFOB) encapsulation by solvent emulsion-evaporation, a marked influence of surfactants has been observed. While sodium cholate leads to spherical capsules of homogeneous thickness, sodium taurocholate induces to the formation of "acorn"-particles with one hemisphere of PFOB and another one of PLGA, and polyvinyl alcohol is responsible for the coexistence of both morphologies. Whereas the theoretical model proposed by Torza and Mason [J. Colloid Interface Sci. 33 (1970) 67] fails to predict the observed morphologies, microscopic observations of the evaporation and interfacial tension measurements provide an insight into the mechanism of formation of these structures. Most probably, there is a competition between PLGA and the surfactant stabilizing the emulsion at the dichloromethane-water interface. If PLGA is able to adsorb at the interface, the core-shell morphology is obtained, otherwise the acorn morphology is preferentially formed. When the surfactant rearrangement at the interface is long (>30 min), a coexistence of morphologies can be obtained.
authors.affiliation: Univ Paris Sud, UMR CNRS 8612, Faculté de Pharmacie, Châtenay-Malabry, France.
authors.forename: Emilia
authors.initials: E
authors.lastname: Pisani
authors.forename: Elias
authors.initials: E
authors.lastname: Fattal
authors.forename: Juliane
authors.initials: J
authors.lastname: Paris
authors.forename: Catherine
authors.initials: C
authors.lastname: Ringard
authors.forename: Véronique
authors.initials: V
authors.lastname: Rosilio
authors.forename: Nicolas
authors.initials: N
authors.lastname: Tsapis
mesh_terms: D003287:Contrast Media / Q000138:chemical synthesis*; D005466:Fluorocarbons / Q000737:chemistry*; D006842:Hydrocarbons, Brominated; D008752:Methylene Chloride / Q000737:chemistry; D008853:Microscopy; D018613:Microscopy, Confocal; D008855:Microscopy, Electron, Scanning; D046529:Microscopy, Electron, Transmission; D053769:Nanocapsules; D011098:Polyglactin 910 / Q000737:chemistry; D020358:Sodium Cholate / Q000494:pharmacology; D013499:Surface Properties; D013501:Surface-Active Agents / Q000494:pharmacology; D013656:Taurocholic Acid / Q000494:pharmacology; D014463:Ultrasonography / Q000379:methods; D014867:Water / Q000737:chemistry
chemical_list: D003287:Contrast Media; D005466:Fluorocarbons; D006842:Hydrocarbons, Brominated; D053769:Nanocapsules; D013501:Surface-Active Agents; D014867:Water; D011098:Polyglactin 910; D008752:Methylene Chloride; D013656:Taurocholic Acid; D020358:Sodium Cholate; C003072:perflubron