Biophysics and Interfaces Group, Department of Applied Physics, Faculty of Physics, University of Santiago de Compostela, E-15782 Santiago de Compostela, Spain.
J Colloid Interface Sci. 2012 Feb 1;367(1):193-8. doi: 10.1016/j.jcis.2011.10.006. Epub 2011 Oct 12.
The influence of La(3+) on the colloidal stability of liposomes made up by two zwitterionic phospholipids, 1,2-dipalmitoyl-sn-glycero-3-phosphocholine (DPPC) and 1-palmitoyl-2-[16-fluoropalmitoyl-phosphatidylcholine (F-DPPC), in aqueous media has been investigated by dynamic light scattering and electrophoretic mobility. The critical aggregation concentration (c.a.c.) of La(3+) for F-DPPC and DPPC liposomes were experimentally obtained, and the results were compared with theoretical predictions using the Derjaguin-Landau-Verwey-Overbeek theory. In order to evaluate the influence of the state of the bilayer on the stability of liposomes, all experiments were performed at temperatures below and above the chain-melting phase-transition temperature of lipids (transition temperature of lipids). Changes in the size of both types of liposomes and high values of polydispersity in the presence of La(3+) showed that these ions induce aggregation of liposomes at 25 °C and at 60 °C. At 25 °C, when the bilayer of F-DPPC liposomes is interdigited, DPPC liposomes are more resistant to aggregation than the liposomes formed with F-DPPC. However, this difference disappears at 60 °C, when both bilayers have the same conformation. The experimental results also indicate that the c.a.c. is higher at 60 °C than at 25 °C for both types of liposomes. In fact, it has been observed by dynamic light scattering measurements that aggregation of liposomes at 25 °C can be prevented by increasing the solution temperature for La(3+) concentrations near to the c.a.c. Moreover, the behavior of these liposomes in the presence of the ion was studied at temperatures above and below the transition temperature of the phospholipids.
La(3+) 对由两种两性离子磷脂组成的脂质体（1,2-二棕榈酰-sn-甘油-3-磷酸胆碱（DPPC）和 1-棕榈酰-2-[16-氟棕榈酰基-磷酸胆碱（F-DPPC））在水介质中的胶体稳定性的影响通过动态光散射和电泳迁移率进行了研究。实验获得了 F-DPPC 和 DPPC 脂质体的 La(3+) 的临界聚集浓度（c.a.c.），并将结果与使用 Derjaguin-Landau-Verwey-Overbeek 理论的理论预测进行了比较。为了评估双层状态对脂质体稳定性的影响，所有实验均在低于和高于脂质相变温度（脂质相变温度）的温度下进行。在存在 La(3+)的情况下，两种类型的脂质体的粒径变化和高的多分散性表明这些离子在 25°C 和 60°C 下诱导脂质体聚集。在 25°C 时，当 F-DPPC 脂质体的双层是互贯时，与形成 F-DPPC 的脂质体相比，DPPC 脂质体更能抵抗聚集。然而，当两个双层具有相同的构象时，这种差异在 60°C 时消失。实验结果还表明，对于两种类型的脂质体，c.a.c.在 60°C 时高于在 25°C 时。事实上，通过动态光散射测量观察到，通过升高溶液温度可以防止 La(3+)浓度接近 c.a.c.时在 25°C 下的脂质体聚集。此外，在高于和低于磷脂相变温度的温度下研究了这些脂质体在离子存在下的行为。
