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Accueil du site > Séminaires, conférences > Séminaires du LIP > Séminaires en 2006 > Polymeric nano/microcapsules of liquid perfluorocarbons for ultrasonic imaging : physical and ultrasonic characterization.

Polymeric nano/microcapsules of liquid perfluorocarbons for ultrasonic imaging : physical and ultrasonic characterization.

Date : 13/01/2006 à 14h00

Intervenants :
- Nicolas Tsapis, Laboratoire de Pharmacie Galénique Faculté de Médecine, Université Paris Sud, UMR 8612 CNRS.

Résumé :

Ultrasonic imaging is a widely available, non invasive and cost-effective diagnostic modality, but clinical Doppler is not able to image vessels smaller than 200 microns in diameter thus preventing the mapping of the capillary network of an organ. Commercial Ultrasound Contrast Agents (UCAs), consisting of encapsulated gas microbubbles injected intravenously, enable only a qualitative visualization of the microvascularization for a short period of time since UCAs are rather unstable. The development of more stable UCAs is therefore of importance for an improved efficacy of many diagnostic applications. We have developed a process to obtain nano/microcapsules with a single core of liquid perfluorocarbons within a biodegradable polymeric shell of homogeneous thickness. The polymer shell should improve the stability of the capsules as compared to UCAs stabilized by a monomolecular layer, while the acoustic impedance of the perfluorocarbons should insure their echogenicity. These capsules have been optimized to encapsulate several liquid perfluorocarbons : perfluorohexane, perfluorodecalin and perfluorooctyl bromide. This system is rather versatile : the mean size of the capsules can be varied between 25 microns and 60 nm, the thickness to radius ratio (T/R) can be easily modulated by simply modifying the polymer to perfluorocarbon ratio. T/R does not depend on the size of the capsules and is comprised between 0.2 and 0.6. The dependence of the echogenic properties of the capsules with their size and their T/R has yet to be studied experimentally before this system can be evaluated in vivo.