Physicochemical characteristics of self-assembled nanoparticles based on glycol chitosan bearing 5β-cholanic acid
Physicochemical characteristics of self-assembled nanoparticles based on glycol chitosan bearing 5β-cholanic acid
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DOI：
10.1021/la0350608
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发表时间：
2003-11-25
期刊：
影响因子：
3.9
通讯作者：
Kim, IS
中科院分区：
文献类型：
--
作者：
Kwon, S;Park, JH;Kim, IS
采用核磁共振氢谱、动态光散射、荧光光谱和透射电子显微镜研究了5 β-胆甾烷酸（5 β-cholanic acid，5 β-cholanic acid）与乙二醇壳聚糖（glycol chitosans，HGC）共价键合后的疏水改性HGC的自聚集行为和微观特征。HGC在水相中通过与乙二醇壳聚糖连接的疏水性5 β-胆烷酸之间的分子内或分子间缔合形成自聚集体。HGCs的临界聚集浓度（cacs）依赖于5 β-胆烷酸的取代度（DS），且显著低于低分子量表面活性剂。自聚集体的平均直径随着5 β-胆烷酸取代度的增加而减小，这是因为形成了紧密的疏水内核。TEM图像表明，在HGC的基础上，自聚集体的形状是球形的。芘在自聚集体溶液中的分配平衡常数（K-v）表明，取代度的增加增强了自聚集体内核的疏水性。通过使用氯化十六烷基吡啶的荧光猝灭法估计的每个疏水微区的5 β-胆烷酸的聚集数随着DS的增加而增加，这表明需要几个HGC链来形成一个疏水微区。
The self-aggregation behavior and microscopic characteristics of hydrophobically modified glycol chitosans (HGCs), prepared by covalent attachment of 5beta-cholanic acid to glycol chitosan, were investigated by using H-1 NMR, dynamic light scattering, fluorescence spectroscopy, and transmission electron microscopy (TEM). The HGCs formed self-aggregates in an aqueous phase by intra- or intermolecular association between hydrophobic 5beta-cholanic acids attached to glycol chitosan. The critical aggregation concentrations (cacs) of the HGCs were dependent on the degree of substitution (DS) of 5beta-cholanic acid and were significantly lower than those of low molecular weight surfactants. The mean diameters of the self-aggregates decreased with the increase in the DS of 5beta-cholanic acid because of the formation of compact hydrophobic inner cores. The TEM images demonstrated that the shape of the self-aggregates, on the basis of the HGCs, is spherical. The partition equilibrium constants (K-v) of pyrene, measured in the self-aggregate solutions of the HGCs, indicated that the increase in the DS enhances the hydrophobicity of inner core of self-aggregates. The aggregation number of 5beta-cholanic acid per one hydrophobic microdomain, estimated by the fluorescence quenching method using cetylpyridinium chloride, increased with increasing the DS, which suggested that several HGC chains were needed to form one hydrophobic domain.