Detailed structure of hairy mixed micelles formed by phosphatidylcholine and PEGylated phospholipids in aqueous media
Detailed structure of hairy mixed micelles formed by phosphatidylcholine and PEGylated phospholipids in aqueous media
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DOI：
10.1021/la047588y
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发表时间：
2005-04-12
期刊：
影响因子：
3.9
通讯作者：
Hjelm, RP
中科院分区：
文献类型：
--
作者：
Arleth, L;Ashok, B;Hjelm, RP
研究了混合蛋黄磷脂酰胆碱（PC）和聚乙二醇（PEG）修饰的二硬脂酰磷脂酰乙醇胺（DSPE）的水分散体，目的是确定形成的混合胶束的形状、大小和构象。样品在DSPEPEG与PC的摩尔比范围内（[DSPEPEG/PC]从100:0到30:70），分别用DSPEPEG2000和DSPEPEG5000制备，其中2000和5000是PEG链的摩尔质量。利用小角x射线散射（SAXS）和小角中子散射（SANS）研究了颗粒的形状和内部结构。x射线和中子的胶束对比不同，通过结合SANS和SAXS，获得了关于胶束结构的互补信息。通过将胶束模型同时拟合到SANS和SAXS数据，以自洽的方式确定了胶束的详细结构。一般来说，具有疏水核心的胶束模型与散射数据很好地吻合，该胶束被致密的亲水性层包围，亲水性层又被附着在外表面的高斯随机线圈形式的聚乙二醇链冠包围。高DSPEPEG含量时，形成近似球形的胶束。随着PC含量的增加，胶束拉长，在DSPEPEG/PC比为30:70时，形成了长度大于1000 a的棒状胶束。我们证明，通过混合DSPEPEG和PC，在控制粒子形状方面获得了相当大的自由度。我们的结果表明，电晕中的PEG链处于相对不受干扰的高斯随机线圈构象中，即使这些链远高于线圈-线圈重叠浓度，因此相互穿透。这一观察结果与观察到的生长行为相结合，质疑了“蘑菇-刷子”转变是决定颗粒形状的单一主导因素，这是以前的理论工作所假设的（Hristova， K.; Needham， D. Macromolecules 1995,28, 991-1002）。
Aqueous dispersions of mixed egg yolk phosphatidylcholine (PC) and poly(ethylene glycol) (PEG) modified distearoyl phosphatidylethanolamine (DSPE) were investigated with the purpose of determining shape, size, and conformation of the formed mixed micelles. The samples were prepared at a range of DSPEPEG to PC molar ratios ([DSPEPEG/PC] from 100:0 to 30:70) and with, respectively, DSPEPEG2000 and DSPEPEG5000, where 2000 and 5000 refer to the molar masses of the PEG chains. Particle shape and internal structure were studied using small-angle X-ray scattering (SAXS) and small-angle neutron scattering (SANS). The contrast of the micelles is different for X-rays and neutrons, and by combining SANS and SAXS, complementary information about the micelle structure was obtained. The detailed structure of the micelles was determined in a self-consistent way by fitting a model for the micelles to SANS and SAXS data simultaneously. In general, a model for the micelles with a hydrophobic core, surrounded by a dense hydrophilic layer that is again surrounded by a corona of PEG chains in the form of Gaussian random coils attached to the outer surface, is in good agreement with the scattering data. At high DSPEPEG contents, nearly spherical micelles are formed. As the PC content increases the micelles elongate, and at a DSPEPEG/PC ratio of 30:70, rodlike micelles longer than 1000 A are formed. We demonstrate that by mixing DSPEPEG and PC a considerable latitude in controlling the particle shape is obtained. Our results indicate that the PEG chains in the corona are in a relatively unperturbed Gaussian random coil conformation even though the chains are far above the coil-coil overlap concentration and, therefore, interpenetrating. This observation in combination with the observed growth behavior questions that the "mushroom-brush" transition is the single dominating factor for determining the particle shape as assumed in previous theoretical work (Hristova, K.; Needham, D. Macromolecules 1995, 28, 991-1002).