On the Effect of Ca2+ and La3+ on the Colloidal Stability of Liposomes

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• 作者：Juan Sabí ; n ; Gerardo Prieto ; Paula V. Messina ; Juan M. Ruso ; Roque Hidalgo-Alvarez ; and Fé ; lix Sarmiento
• 刊名：Langmuir
• 出版年：2005
• 出版时间：November 22, 2005
• 年：2005
• 卷：21
• 期：24
• 页码：10968 - 10975
• 全文大小：323K
• 年卷期：v.21,no.24(November 22, 2005)
• ISSN：1520-5827

文摘

This work deals with the effect of Ca²⁺ and La³⁺ on the colloidal stability of phosphatidylcholine (PC)liposomes in aqueous media. As physical techniques, nephelometry, photon correlation spectroscopy,electrophoretic mobility, and surface tension were used. The theoretical predictions of the colloidal stabilityof liposomes were followed using the Derjaguin-Landau-Verwey-Overbeek theory. Changes in the sizeof liposomes and high polydispersity values were observed as La³⁺ concentration increases, suggestingthat this cation induces the aggregation of liposomes. However, changes in polydispersity were not observedwith Ca²⁺, suggesting a coalescence mechanism or fusion of liposomes. The stability factor (W), calculatedfrom the nephelometry measurements indicated that aggregation/fusion occurs at a critical concentration(c.c.) of 0.3 and 0.7 M for La³⁺ and Ca²⁺, respectively. To gain a better insight into the interaction mechanismbetween the liposomes and the studied ions, the interaction between PC monolayers and Ca²⁺ and La³⁺was studied. Changes in the surface area per lipid molecule (A₀) in the monolayer at the c.c. values werefound for both ions, with a more pronounced effect in the case of Ca²⁺. This corresponds with a largerreduction of the steric repulsive interaction between the headgroups at the phospholipid membrane (_head).The experimental result validates the hypothesis made on the liposome fusion in the presence of Ca²⁺ andliposome aggregation in the presence of La³⁺. These aggregation mechanisms have also been confirmedby transmission electron microscopy.