Department of Pharmaceutical Technology, Faculty of Pharmacy, Panepistimioupolis Zografou 15771, University of Athens, Athens, Greece.
Int J Pharm. 2012 Jul 1;430(1-2):65-73. doi: 10.1016/j.ijpharm.2012.03.048. Epub 2012 Apr 1.
The present study deals with the physicochemical characterization (size, polydispersity, ζ-potential) of dipalmitoylphosphatidylcholine (DPPC) liposomes and DPPC:cholesterol (chol) (9:1 molar ratio) liposomes, and the determination of their fractal dimension (mass fractal (d(f)) and surface fractal (d(s))), in an aqueous (HPLC grade water) and in a biological (fetal bovine serum - FBS) medium. Dynamic, static and electrophoretic light scattering and fluorescence spectroscopy are used as experimental techniques to elucidate the structure and physicochemical parameters of liposomes in an ageing study in two different media, as well as their structural response in changes in concentration and temperature. The extended DLVO theory would be the tool to explain the phenomenology of the colloidal behavior in these systems and of their aggregation process. The fractal dimensionality of DPPC liposomes was decreased while for DPPC:cholesterol (9:1) it remained unaffected in the two dispersion media. The structure of the liposomal systems, the process kinetics, and the fractal dimension are consistent with the diffusion-limited cluster aggregation (DLCA) and reaction-limited cluster aggregation (RLCA) models. On the contrary, hydrodynamic radius (R(h)) was found to be stable during the variations of colloidal system conditions, especially due to concentration changes. Finally, we suggest that this study can be a rational road map to design advanced Drug Delivery nano Systems (aDDnSs) with improved pharmacokinetic profile which could be considered as crucial for their effectiveness.
本研究对二棕榈酰磷脂酰胆碱（DPPC）脂质体和 DPPC：胆固醇（chol）（9:1 摩尔比）脂质体的物理化学特性（大小、多分散性、ζ-电位）进行了研究，并测定了它们在水相（HPLC 级水）和生物相（胎牛血清-FBS）中的分形维数（质量分形（d(f)) 和表面分形（d(s))）。动态、静态和电泳光散射以及荧光光谱被用作实验技术，以阐明在两种不同介质中的老化研究中脂质体的结构和物理化学参数，以及它们在浓度和温度变化下的结构响应。扩展的 DLVO 理论将是解释这些系统中胶体行为的现象学及其聚集过程的工具。DPPC 脂质体的分形维数降低，而 DPPC：胆固醇（9:1）在两种分散介质中保持不变。脂质体系统的结构、过程动力学和分形维数与扩散限制簇聚集（DLCA）和反应限制簇聚集（RLCA）模型一致。相反，在胶体系统条件的变化过程中，发现流体力学半径（R(h)) 是稳定的，特别是由于浓度的变化。最后，我们认为这项研究可以为设计具有改善药代动力学特征的先进药物输送纳米系统（aDDnSs）提供合理的路线图，这被认为对其有效性至关重要。
