Department of Physics and Astronomy, University of New Mexico, Albuquerque, New Mexico 87008, USA.
Langmuir. 2010 Sep 21;26(18):14774-81. doi: 10.1021/la102583k.
The 1.1 MHz ultrasound response of micrometer-scale perfluorobutane gas bubbles, coated with a mixture of 90 mol % saturated phospholipid (disteroylphosphatidylcholine, DSPC) or unsaturated phospholipid (dioleoylphosphatidylcholine, DOPC) and 10 mol % PEG-lipid, was studied by optical microscopy. Uncoated bubbles were also studied. Bubbles, resting buoyantly against the wall of a polystyrene cuvette, were exposed to brief pulses of ultrasound (∼200 kPa amplitude) at a repetition rate of 25 Hz; images of the bubbles were taken after every other pulse. The coating had little effect on the initial response: large (>10 μm diameter) bubbles showed no size change, while smaller bubbles rapidly shrank (or fragmented) to reach a stable or metastable diameter-ca. 2 μm for coated bubbles and 4 μm for uncoated bubbles. The coating had a significant effect on further bubble evolution: after reaching a metastable size, uncoated bubbles and DOPC-coated bubbles continued to shrink slowly and ultimately vanished entirely, while DSPC-coated bubbles did not change perceptibly during the duration of the exposure. Numerical modeling using the modified Herring equation showed that the size range in which DSPC bubbles responded does correspond well with the bubble resonance; the long-term stability of these bubbles may be related to the ability of the DSPC to form a two-dimensional solid at ambient temperature or to phase separate from the PEG-lipid.
通过光学显微镜研究了涂有 90 mol%饱和磷脂（二硬脂酰基磷脂酰胆碱，DSPC）或不饱和磷脂（二油酰基磷脂酰胆碱，DOPC）和 10 mol%PEG-脂质混合物的微米级全氟丁烷气体气泡在 1.1 MHz 超声下的响应。还研究了未涂层的气泡。将气泡静置在聚苯乙烯比色皿的壁上，使其浮力平衡，然后用重复率为 25 Hz 的短暂超声脉冲（约 200 kPa 幅度）进行照射；每隔一个脉冲就会拍摄气泡的图像。涂层对初始响应几乎没有影响：大（>10 μm 直径）气泡没有直径变化，而较小的气泡迅速收缩（或碎裂）至达到稳定或亚稳直径-约 2 μm 的涂层气泡和 4 μm 的无涂层气泡。涂层对进一步的气泡演化有显著影响：达到亚稳尺寸后，无涂层气泡和 DOPC 涂层气泡继续缓慢收缩，最终完全消失，而 DSPC 涂层气泡在暴露期间几乎没有明显变化。使用修正的 Herring 方程进行数值模拟表明，DSPC 气泡响应的尺寸范围与气泡共振非常吻合；这些气泡的长期稳定性可能与 DSPC 在环境温度下形成二维固体的能力或与 PEG-脂质相分离有关。
