Aramaki Kenji, Iwata Chikahiro, Mata Jitendra, Maehara Tetsuya, Aburano Daisuke, Sakanishi Yuichi, Kitao Kyuhei
Graduate School of Environment and Information Sciences, Yokohama National University, Tokiwadai 79-7, Hodogaya-ku, Yokohama 240-8501, Japan.
Phys Chem Chem Phys. 2017 Sep 13;19(35):23802-23808. doi: 10.1039/c7cp02585h.
Bicelles are generally formed by phospholipid-based systems and are useful for various applications, such as nanocarriers or membrane protein crystallization. The same disc-like assemblies, nonionic surfactant bicelles (NSBs), can also be formed using nonionic amphiphiles, but this has not been reported extensively. We report a novel NSB system that employs the double-tailed nonionic amphiphile, polyglyceryl dialkyl ether (CCG), which has two alkyl chains and a polyglyceryl group. A symmetric-tail molecule, CCG, formed vesicles, whereas an asymmetric-tail molecule, CCG, formed NSBs through a simple one-step process using ultrasonication. The 1 wt% aqueous solution of CCG was in a two-phase equilibrium of a lamellar phase and a water phase. Transparent dispersion was obtained through ultrasonication treatment. The size distribution in the dispersion was obtained by dynamic light scattering (DLS), resulting in a narrow distribution of around 20 nm in diameter. A negatively-stained transmission electron microscopy (TEM) image showed oblong and spherical shapes, which are typically observed in bicelle-forming systems. A small angle neutron scattering (SANS) measurement well proved bicelle formation by fitting a core-shell bicelle form factor model. The disc thickness and diameter were in agreement with the values obtained by DLS and TEM, respectively. A larger shell thickness at the rim part than at the flat disc part suggested that NSB aggregates have inhomogeneous molecular distribution. Similar to phospholipid systems, the bicelle-forming CCG system produced a defective lamellar phase formation at high surfactant concentrations, whereas a general lamellar phase was formed in the vesicle-forming CCG system.
双分子层囊泡通常由基于磷脂的体系形成，可用于各种应用，如纳米载体或膜蛋白结晶。同样的盘状组装体，即非离子表面活性剂双分子层囊泡（NSB），也可以使用非离子两亲物形成，但这方面的报道并不广泛。我们报道了一种新型的NSB体系，该体系采用双尾非离子两亲物聚甘油二烷基醚（CCG），它具有两条烷基链和一个聚甘油基团。对称尾分子CCG形成囊泡，而非对称尾分子CCG通过超声处理的简单一步法形成NSB。CCG的1 wt%水溶液处于层状相和水相的两相平衡中。通过超声处理获得透明分散体。通过动态光散射（DLS）获得分散体中的尺寸分布，结果显示直径约20 nm的窄分布。负染色透射电子显微镜（TEM）图像显示出长圆形和球形，这是在双分子层囊泡形成体系中通常观察到的形状。小角中子散射（SANS）测量通过拟合核壳双分子层囊泡形状因子模型很好地证明了双分子层囊泡的形成。盘厚度和直径分别与通过DLS和TEM获得的值一致。边缘部分的壳厚度大于平盘部分，这表明NSB聚集体具有不均匀的分子分布。与磷脂体系类似，形成双分子层囊泡的CCG体系在高表面活性剂浓度下产生有缺陷的层状相形成，而在形成囊泡的CCG体系中形成一般的层状相。
