Laboratory of Food Process Engineering, ETH Zurich, Schmelzbergstrasse 9, 8092 Zurich, Switzerland.
J Phys Chem B. 2010 Jan 14;114(1):174-86. doi: 10.1021/jp907442e.
Magnetic fields were applied as a structuring force on phospholipid-based vesicular systems, using paramagnetic lanthanide ions as magnetic handles anchored to the vesicle membrane. Different vesicle formulations were investigated using small angle neutron scattering (SANS) in a magnetic field of up to 8 T, cryo-transmission electron microscopy (cryo-TEM), (31)P NMR spectroscopy, dynamic light scattering (DLS), and permeability measurements with a fluorescent water-soluble marker (calcein). The investigated vesicle formulations consisted usually of 80 mol % of the phospholipid 1-palmitoyl-2-oleoyl-sn-glycero-3-phosphocholine (POPC) and 20 mol % of a chelator lipid (DMPE-DTPA; 1,2-dimyristoyl-sn-glycero-3-phosphoethanolamine-diethylenetriaminepentaacetate) with complexed lanthanide ions (Tm(3+), Dy(3+), or La(3+)), and the total lipid concentration was 15 mM. Vesicles containing the paramagnetic lanthanide Tm(3+) or Dy(3+) exhibited a temperature-dependent response to magnetic fields, which can be explained by considering the formation of lipid domains, which upon reaching a critical size become alignable in a magnetic field. The features of this "magnetic field alignable domain model" are as follows: with decreasing temperature (from 30 to 2.5 degrees C) solid domains, consisting mainly of the higher melting phospholipid (DMPE-DTPA.lanthanide), begin to form and grow in size. The domains assemble the large magnetic moments conferred by the lanthanides and orient in magnetic fields. The direction of alignment depends on the type of lanthanide used. The domains orient with their normal parallel to the magnetic field with thulium (Tm(3+)) and perpendicular with dysprosium (Dy(3+)). No magnetic field alignable domains were observed if DMPE-DTPA is replaced either by POPE-DTPA (1-palmitoyl-2-oleoyl-sn-glycero-3-phosphoethanolamine-diethylenetriamine-pentaacetate) or by DMPC (1,2-dimyristoyl-sn-glycero-3-phosphocholine).
磁场被用作磷脂基囊泡系统的结构化力，使用顺磁镧系元素离子作为锚定在囊泡膜上的磁性把手。使用小角度中子散射 (SANS) 在高达 8 T 的磁场中、低温透射电子显微镜 (cryo-TEM)、(31)P NMR 光谱、动态光散射 (DLS) 和带有荧光水溶性标记物 (钙黄绿素) 的渗透性测量研究了不同的囊泡配方。研究的囊泡配方通常由 80 mol%的磷脂 1-棕榈酰基-2-油酰基-sn-甘油-3-磷酸胆碱 (POPC) 和 20 mol%的螯合脂质 (DMPE-DTPA；1,2-二肉豆蔻酰基-sn-甘油-3-磷酸乙醇胺二乙撑三胺五乙酸) 与络合镧系元素离子 (Tm(3+)、Dy(3+) 或 La(3+)）组成，总脂质浓度为 15 mM。含有顺磁镧系元素 Tm(3+) 或 Dy(3+) 的囊泡表现出对磁场的温度依赖性响应，这可以通过考虑脂质域的形成来解释，当达到临界尺寸时，这些脂质域在磁场中变得可排列。这种“磁场可排列域模型”的特征如下：随着温度降低（从 30 到 2.5 摄氏度），主要由较高熔点的磷脂（DMPE-DTPA.镧系元素）组成的固态域开始形成并增大尺寸。这些域组装由镧系元素赋予的大磁矩并在磁场中取向。取向的方向取决于所使用的镧系元素的类型。如果 DMPE-DTPA 被 POPE-DTPA（1-棕榈酰基-2-油酰基-sn-甘油-3-磷酸乙醇胺二乙撑三胺五乙酸）或 DMPC（1,2-二肉豆蔻酰基-sn-甘油-3-磷酸胆碱）替代，则不会观察到磁场可排列的域。
