title: Influence of temperature on the colloidal stability of the F-DPPC and DPPC liposomes induced by lanthanum ions.
abstract: 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.
authors: Biophysics and Interfaces Group, Department of Applied Physics, Faculty of Physics, University of Santiago de Compostela, E-15782 Santiago de Compostela, Spain.
authors: Paula
authors: P
authors: Toimil
authors: Rocío
authors: R
authors: Daviña
authors: Juan
authors: J
authors: Sabín
authors: Gerardo
authors: G
authors: Prieto
authors: Félix
authors: F
authors: Sarmiento
mesh_terms: D015060:1,2-Dipalmitoylphosphatidylcholine / Q000737:chemistry*; D003102:Colloids / Q000737:chemistry; D007477:Ions / Q000737:chemistry; D007811:Lanthanum / Q000737:chemistry*; D008081:Liposomes / Q000737:chemistry*; D010316:Particle Size; D044367:Phase Transition; D010713:Phosphatidylcholines / Q000737:chemistry*; D013696:Temperature
chemical_list: C115319:1-palmitoyl-2-(16-fluoropalmitoyl)phosphatidylcholine; D003102:Colloids; D007477:Ions; D008081:Liposomes; D010713:Phosphatidylcholines; D015060:1,2-Dipalmitoylphosphatidylcholine; D007811:Lanthanum