title: Complex interfaces in "phase-change" contrast agents.
abstract: In this paper we report on the study of the interface of hybrid shell droplets encapsulating decafluoropentane (DFP), which exhibit interesting potentialities for ultrasound (US) imaging. The fabrication of the droplets is based on the deposition of a dextran methacrylate layer onto the surface of surfactants. The droplets have been stabilized against coalescence by UV curing, introducing crosslinks in the polymer layer and transforming the shell into an elastomeric membrane with a thickness of about 300 nm with viscoelastic behaviour. US irradiation induces the evaporation of the DFP core of the droplets transforming the particles into microbubbles (MBs). The presence of a robust crosslinked polymer shell introduces an unusual stability of the droplets also during the core phase transition and allows the recovery of the initial droplet state after a few minutes from switching off US. The interfacial tension of the droplets has been investigated by two approaches, the pendant drop method and an indirect method, based on the determination of the liquid ↔ gas transition point of DFP confined in the droplet core. The re-condensation process has been followed by capturing images of single MBs by confocal microscopy. The time evolution of MB relaxation to droplets was analysed in terms of a modified Church model to account for the structural complexity of the MB shell, i.e. a crosslinked polymer layer over a layer of surfactants. In this way the microrheology parameters of the shell were determined. In a previous paper (Chem. Commun., 2013, 49, 5763-5765) we showed that these systems could be used as ultrasound contrast agents (UCAs). In this work we substantiate this view assessing some key features offered by the viscoelastic nature of the droplet shell.
authors.affiliation: Dipartimento di Scienze e Tecnologie Chimiche, Università di Roma Tor Vergata, Via della Ricerca Scientifica 1, 00133 Rome, Italy. paradossi@stc.uniroma2.it.
authors.forename: Sabrina
authors.initials: S
authors.lastname: Capece
authors.affiliation: Dipartimento di Scienze e Tecnologie Chimiche, Università di Roma Tor Vergata, Via della Ricerca Scientifica 1, 00133 Rome, Italy. paradossi@stc.uniroma2.it and Dipartimento di Fisica, Università di Roma Sapienza, P.le Aldo Moro 5, 00185 Rome, Italy.
authors.forename: Fabio
authors.initials: F
authors.lastname: Domenici
authors.affiliation: Dipartimento di Fisica, Università di Roma Sapienza, P.le Aldo Moro 5, 00185 Rome, Italy.
authors.forename: Francesco
authors.initials: F
authors.lastname: Brasili
authors.affiliation: Dipartimento di Scienze e Tecnologie Chimiche, Università di Roma Tor Vergata, Via della Ricerca Scientifica 1, 00133 Rome, Italy. paradossi@stc.uniroma2.it.
authors.forename: Letizia
authors.initials: L
authors.lastname: Oddo
authors.affiliation: Dipartimento di Scienze e Tecnologie Chimiche, Università di Roma Tor Vergata, Via della Ricerca Scientifica 1, 00133 Rome, Italy. paradossi@stc.uniroma2.it.
authors.forename: Barbara
authors.initials: B
authors.lastname: Cerroni
authors.affiliation: INAIL - Settore Ricerca Certificazione e Verifica - DITSIPIA, Via Fontana Candida, 1 Monteporzio Catone, 00040 Italy.
authors.forename: Angelico
authors.initials: A
authors.lastname: Bedini
authors.affiliation: Dipartimento di Fisica, Università di Roma Sapienza, P.le Aldo Moro 5, 00185 Rome, Italy.
authors.forename: Federico
authors.initials: F
authors.lastname: Bordi
authors.affiliation: Dipartimento di Scienze e Tecnologie Chimiche, Università di Roma Tor Vergata, Via della Ricerca Scientifica 1, 00133 Rome, Italy. paradossi@stc.uniroma2.it.
authors.forename: Ester
authors.initials: E
authors.lastname: Chiessi
authors.affiliation: Dipartimento di Scienze e Tecnologie Chimiche, Università di Roma Tor Vergata, Via della Ricerca Scientifica 1, 00133 Rome, Italy. paradossi@stc.uniroma2.it.
authors.forename: Gaio
authors.initials: G
authors.lastname: Paradossi
mesh_terms: D001672:Biocompatible Materials / Q000737:chemistry; D002152:Calorimetry, Differential Scanning; D003287:Contrast Media / Q000737:chemistry*; D003911:Dextrans / Q000737:chemistry; D000067493:Dynamic Light Scattering; D045423:Microbubbles; D018625:Microscopy, Atomic Force; D018613:Microscopy, Confocal; D011108:Polymers / Q000737:chemistry; D013500:Surface Tension; D013501:Surface-Active Agents / Q000737:chemistry; D013818:Thermogravimetry; D014463:Ultrasonography
chemical_list: D001672:Biocompatible Materials; D003287:Contrast Media; D003911:Dextrans; D011108:Polymers; D013501:Surface-Active Agents