Kodama Tetsuya, Tomita Noriko, Horie Sachiko, Sax Nicolas, Iwasaki Hiroko, Suzuki Ryo, Maruyama Kazuo, Mori Shiro, Manabu Fukumoto
Graduate School of Biomedical Engineering, Tohoku University, 2-1 Seiryo, Aoba, Sendai, 980-8575, Japan.
J Electron Microsc (Tokyo). 2010;59(3):187-96. doi: 10.1093/jmicro/dfp056. Epub 2009 Nov 11.
Sonoporation is achieved by ultrasound-mediated destruction of ultrasound contrast agents (UCA) microbubbles. For this, UCAs must be tissue specific and have good echogenicity and also function as drug carriers. Previous studies have developed acoustic liposomes (ALs), liposomes that encapsulate phosphate buffer solution and perfluoropropane (C(3)F(8)) gas and function as both UCAs and drug carriers. Few studies have examined the co-existence of gas and liquid in ALs. This study aims to elucidate AL structure using TEM. The size, zeta potential and structure of ALs were compared with those of two other UCAs, human albumin shell bubbles (ABs; Optison) and lipid bubbles (LBs). ABs and LBs encapsulate the C(3)F(8) gas. Particle size was measured by dynamic light scattering. The zeta potential was determined by the Smoluchowski equation. UCA structure was investigated by TEM. ALs were approximately 200 nm in size, smaller than LBs and ABs. ALs and LBs had almost neutral zeta potentials whereas AB values were strongly negative. The negative or double staining TEM images revealed that approximately 20% of ALs contained both liquid and gas, while approximately 80% contained liquid alone (i.e. nonacoustic). Negative staining AB images indicated electron beam scattering near the shell surface, and albumin was detected in filament form. These findings suggest that AL is capable of carrying drugs and high-molecular-weight, low-solubility gases.
超声穿孔是通过超声介导破坏超声造影剂（UCA）微泡来实现的。为此，UCA必须具有组织特异性、良好的回声性，并且还能作为药物载体。先前的研究已经开发出了声学脂质体（AL），即包裹磷酸盐缓冲溶液和全氟丙烷（C₃F₈）气体并兼具UCA和药物载体功能的脂质体。很少有研究考察AL中气体和液体的共存情况。本研究旨在用透射电子显微镜（TEM）阐明AL的结构。将AL的大小、ζ电位和结构与另外两种UCA，即人白蛋白壳泡（AB；Optison）和脂质泡（LB）进行比较。AB和LB包裹C₃F₈气体。通过动态光散射测量颗粒大小。ζ电位由斯莫卢霍夫斯基方程确定。通过TEM研究UCA的结构。AL的大小约为200 nm，比LB和AB小。AL和LB的ζ电位几乎呈中性，而AB的值则为强负值。阴性或双重染色的TEM图像显示，约20%的AL同时含有液体和气体，而约80%仅含有液体（即非声学的）。阴性染色的AB图像表明在壳表面附近有电子束散射，并且检测到丝状的白蛋白。这些发现表明AL能够携带药物以及高分子量、低溶解度的气体。
