Microbubbles Coated with Disaturated Lipids and DSPE-PEG2000: Phase Behavior, Collapse Transitions, and Permeability
Microbubbles Coated with Disaturated Lipids and DSPE-PEG2000: Phase Behavior, Collapse Transitions, and Permeability
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DOI：
10.1021/la803774q
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发表时间：
2009-03-17
期刊：
影响因子：
3.9
通讯作者：
Longo, Marjorie L.
中科院分区：
文献类型：
--
作者：
Lozano, Monica M.;Longo, Marjorie L.
饱和二酰基（二饱和）磷脂酰胆碱（PC）与脂聚合物二硬脂酰磷脂酰乙醇胺（DSPE）-聚乙二醇分子量2000（PEG 2000）混合，在水包空气微米级气泡（微泡）的空气-水界面处自组装为单层，类似于领先的医用超声造影剂（UCA）上的涂层（外壳）。该系统的特点是在这里研究的DSPE-PEG 2000种类和PC链长的单层涂层相行为的影响，崩溃，脱落，和空气传输阻力和微泡溶解速率和表面轮廓。使用溶解微泡的荧光显微镜，我们发现所有链长（n = 14-20）的膜微观结构和塌陷行为指示主要为凝聚相单层，不像含有聚乙二醇40硬脂酸酯（PEG 40 S）的类似涂层是膨胀相或共存的膨胀-凝聚相单层。此外，我们观察到一种新的表面屈曲类型的行为与所有的链长，通过明场显微镜，空气-水界面连续出现粗糙（而不是周期性粗糙和光滑），这种行为最常见的n = 16。在相关的统计频率的这种行为与单层微观结构，我们建议，它产生于一个缓慢的成核率的崩溃结构在凝聚-凝聚相界面，不存在于含有PEG 40 S的系统。通过对溶解（半径与时间）数据进行建模，我们获得了每个链长的薄膜空气传输阻力（R-壳层），然后将其拟合到链长相关的能量势垒模型。重要的是，与先前研究的含有PEG 40 S的膜相比，指前因子类似于10倍高，并且微泡持续类似于4倍长（在固定的溶解氧含量下从15 μ m）。我们将含有DSPE-PEG 2000的微泡涂层的独特稳定性属性归因于该分子形成凝聚相单层的倾向，使得单层涂层接近一个连续凝聚域的属性。
Saturated diacyl (disaturated) phosphatidylcholine (PC) mixed with the lipopolymer distearoylphosphatidylethanolamine (DSPE)-polyethyleneglycol molecular weight 2000 (PEG2000) self-assemble as a monolayer at the air-water interface of air-in-water micrometer-scale bubbles (microbubbles), similar to coatings (shells) on leading medical ultrasound contrast agents (UCAs). This system is characterized here to study the impact of the DSPE-PEG2000 species and PC chain-length on the monolayer coating phase behavior, collapse, shedding, and air transport resistance and microbubble dissolution rate and surface contour. Using fluorescence microscopy of dissolving microbubbles, we found that film microstructure and collapse behavior for all chain lengths (n = 14-20) was indicative of primarily condensed phase monolayers, unlike similar coatings containing polyethyleneglycol 40 stearate (PEG40S) that are either expanded phase or coexisting expanded-condensed phase monolayers. Additionally, we observed a new surface buckling type of behavior with all chain lengths, by bright field microscopy, where the air-water interface continuously appears rough (rather than cyclically rough and smooth), with this behavior most frequently observed for n = 16. In correlating the statistical frequency of this behavior with the monolayer microstructure, we propose that it arises from a slowed nucleation rate of collapse structures at condensed-condensed phase interfaces, not present in systems containing PEG40S. By modeling the dissolution (radius vs time) data, we obtained, for each chain length, the film air transport resistance (R-shell) that was then fit to a chain-length-dependent energy barrier model. Importantly, the pre-exponential factor was similar to 10 x higher and the microbubbles persisted similar to 4 x longer (from 15 mu m at a fixed dissolved oxygen content) in comparison to previously studied films containing PEG40S. We attribute the unique stability properties of microbubble coatings containing DSPE-PEG2000 to the propensity of this molecule to form a condensed-phase monolayer, such that the monolayer coatings approach the properties of one continuous condensed domain.