Woodward John T, Meuse Curtis W
Biotechnology Division, Chemical Science and Technology Laboratory, National Institute of Standards and Technology, 100 Bureau Drive, Gaithersburg, MD 20899, USA.
J Colloid Interface Sci. 2009 Jun 15;334(2):139-45. doi: 10.1016/j.jcis.2009.03.007. Epub 2009 Mar 28.
We investigated the process of phospholipid vesicle fusion to a hydrophobic surface using electrochemical impedance spectroscopy (EIS) and atomic force microscopy (AFM). The kinetics of the fusion of dimyristoyl phosphatidylcholine (DMPC) vesicles to an octadecanethiol (ODT) self-assembled monolayer (SAM) was followed with EIS and found to be slower than previously reported observations by surface plasmon resonance. AFM images of the DMPC layer taken at various stages of completion show they are uniform with topography similar to that of the bare ODT SAM. The AFM was used in contact mode to scrape away a portion of a completed DMPC monolayer and the hole was stable for several hours. Surprisingly, the hole remained stable even after the temperature of the system was raised to 38 degrees C, well above the gel transition temperature for DMPC of 23 degrees C. We were unable to scrape holes in the partially completed monolayers. We conclude that in the early stages of monolayer growth the DMPC molecules spread across the ODT surface after vesicle fusion rather than remaining in dense islands. However, when the DMPC monolayer is complete this mobility is lost and the DMPC will not spread into a vacant area.
我们使用电化学阻抗谱（EIS）和原子力显微镜（AFM）研究了磷脂囊泡与疏水表面的融合过程。通过EIS跟踪了二肉豆蔻酰磷脂酰胆碱（DMPC）囊泡与十八烷硫醇（ODT）自组装单分子层（SAM）的融合动力学，发现其比先前通过表面等离子体共振报道的观察结果要慢。在不同完成阶段拍摄的DMPC层的AFM图像显示，它们是均匀的，其形貌与裸露的ODT SAM相似。AFM以接触模式用于刮去一部分已完成的DMPC单分子层，并且该孔在数小时内保持稳定。令人惊讶的是，即使将系统温度升高到38摄氏度，远高于DMPC的凝胶转变温度23摄氏度，该孔仍保持稳定。我们无法在部分完成的单分子层中刮出孔。我们得出结论，在单分子层生长的早期阶段，DMPC分子在囊泡融合后分布在ODT表面，而不是留在密集的岛状区域中。然而，当DMPC单分子层完成时，这种流动性丧失，并且DMPC不会扩散到空白区域。
