Surface phase behavior and microstructure of lipid/PEG-emulsifier monolayer-coated microbubbles
Surface phase behavior and microstructure of lipid/PEG-emulsifier monolayer-coated microbubbles
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DOI：
10.1016/j.colsurfb.2004.03.007
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发表时间：
2004-06-01
影响因子：
5.8
通讯作者：
Longo, ML
中科院分区：
文献类型：
--
作者：
Borden, MA;Pu, G;Longo, ML
结合Langmuir槽法和荧光显微镜研究了生物医学应用中常用的微米级气泡（微气泡）涂层的单层壳的相行为和微观结构。该单层外壳由同源系列饱和酰基链磷脂和含有疏水硬脂酸酯单链和聚乙二醇（PEG）头基的乳化剂组成。peg -乳化剂与膨胀相脂质完全混溶，与凝聚相脂质相分离。相共存的形式是深色凝聚相脂域被明亮的海洋包围，乳化剂丰富的膨胀相。在每一批微泡中都观察到丰富的凝聚相面积分数和畴形态，包括网络和其他新结构。在Langmuir单层中，在加热-冷却然后是压缩-离子膨胀的条件下，以及在微泡壳中经历表面流动和轻微压缩的条件下，可以重现网络域。通过相变温度，结构域尺寸随着冷却速率的增加而减小，在高冷却速率下，结构域分支随着脂酰链长的增加而增加。在接近35 mN/m的表面压力下，乳化剂的挤出可以通过Langmuir等温线的平台来显示，并且可以通过荧光显微镜直接观察到，尽管固体脂质结构域在更高的表面压力下会发生崩溃。压缩的单层超过聚乙二醇乳化剂挤出的表面压力导致一个深色的壳完全由脂质组成。在一定条件下，peg -乳化剂在随后的膨胀中重新掺入。影响壳的形成和演变的因素，以及对微泡在医疗应用的合理设计的影响，进行了讨论。(C) 2004 Elsevier B.V.版权所有
Langmuir trough methods and fluorescence microscopy were combined to investigate the phase behavior and microstructure of monolayer shells coating micron-scale bubbles (microbubbles) typically used in biomedical applications. The monolayer shell consisted of a homologous series of saturated acyl chain phospholipids and an emulsifier containing a single hydrophobic stearate chain and polyethylene glycol (PEG) head group. PEG-emulsifier was fully miscible with expanded phase lipids and phase separated from condensed phase lipids. Phase coexistence was observed in the form of dark condensed phase lipid domains surrounded by a sea of bright, emulsifier-rich expanded phase. A rich assortment of condensed phase area fractions and domain morphologies, including networks and other novel structures, were observed in each batch of microbubbles. Network domains were reproduced in Langmuir monolayers under conditions of heating-cooling followed by compress ion-expansion, as well as in microbubble shells that underwent surface flow with slight compression. Domain size decreased with increased cooling rate through the phase transition temperature, and domain branching increased with lipid acyl chain length at high cooling rates. Squeeze-out of the emulsifier at a surface pressure near 35 mN/m was indicated by a plateau in Langmuir isotherms and directly visualized with fluorescence microscopy, although collapse of the solid lipid domains occurred at much higher surface pressures. Compression of the monolayer past the PEG-emulsifier squeeze-out surface pressure resulted in a dark shell composed entirely of lipid. Under certain conditions, the PEG-emulsifier was reincorporated upon subsequent expansion. Factors that affect shell formation and evolution, as well as implications for the rational design of microbubbles in medical applications, are discussed. (C) 2004 Elsevier B.V. All rights reserved.