Pisani E, Tsapis N, Paris J, Nicolas V, Cattel L, Fattal E
UMR CNRS 8612, School of Pharmacy, Univ. Paris Sud, France, Facoltà di Farmacia, Università degli Studi di Torino, Torino, Italy.
Langmuir. 2006 Apr 25;22(9):4397-402. doi: 10.1021/la0601455.
Ultrasonic imaging is a widely available, noninvasive, and cost-effective diagnostic modality, but vessels smaller than 200 mum in diameter are impossible to visualize. 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 they are rather unstable. In a strategy to develop more stable UCAs, we designed 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 ensure their echogenicity. These capsules have been optimized to encapsulate several liquid perfluorocarbons: perfluorohexane, perfluorodecalin, and perfluorooctyl bromide. The system is rather versatile: the mean size of the capsules can be adjusted between 70 nm and 25 microm and 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 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.
超声成像术是一种广泛可用、非侵入性且具有成本效益的诊断方式，但直径小于200微米的血管无法可视化。商用超声造影剂（UCAs）由静脉注射的包裹气体微泡组成，由于其相当不稳定，只能在短时间内对微血管进行定性可视化。在开发更稳定的UCAs的策略中，我们设计了一个过程，以获得在均匀厚度的可生物降解聚合物壳内具有单个全氟化碳液体核心的纳米/微胶囊。与由单分子层稳定的UCAs相比，聚合物壳应提高胶囊的稳定性，而全氟化碳的声阻抗应确保其回声性。这些胶囊已被优化以包裹几种液体全氟化碳：全氟己烷、全氟萘烷和全氟辛基溴。该系统相当通用：胶囊的平均尺寸可以在70纳米至25微米之间调节，并且通过简单地改变聚合物与全氟化碳的比例，可以很容易地调节厚度与半径比（T/R）。T/R不取决于胶囊的大小，且在0.2至0.6之间。在该系统能够在体内进行评估之前，胶囊的回声特性对其大小和T/R的依赖性还有待通过实验进行研究。
