García-Pérez Ángela, da Silva Marcelo A, Eriksson Jonny, González-Gaitano Gustavo, Valero Margarita, Dreiss Cécile A
Institute of Pharmaceutical Science, King's College London , Franklin-Wilkins Building, 150 Stamford Street, London SE1 9NH, UK.
Langmuir. 2014 Oct 7;30(39):11552-62. doi: 10.1021/la503000z. Epub 2014 Sep 23.
We report the effect of native cyclodextrins (α, β, and γ) and selected derivatives in modulating the self-assembly of the nonionic surfactant polyoxyethylene cholesteryl ether (ChEO10) and its mixtures with triethylene glycol monododecyl ether (C12EO3), which form wormlike micelles. Cyclodextrins (CDs) generally induce micellar breakup through a host-guest interaction with surfactants; instead, we show that a constructive effect, leading to gel formation, is obtained with specific CDs and that the widely invoked host-guest interaction may not be the only key to the association. When added to wormlike micelles of ChEO10 and C12EO3, native β-CD, 2-hydroxyethyl-β-CD (HEBCD), and a sulfated sodium salt of β-CD (SULFBCD) induce a substantial increase of the viscoelasticity, while methylated CDs rupture the micelles, leading to a loss of the viscosity, and the other CDs studied (native α- and γ- and hydroxypropylated CDs) show a weak interaction. Most remarkably, the addition of HEBCD or SULFBCD to pure ChEO10 solutions (which are low-viscosity, Newtonian fluids of small, ellipsoidal micelles) induces the formation of transparent gels. The combination of small-angle neutron scattering, dynamic light scattering, and cryo-TEM reveals that both CDs drive the elongation of ChEO10 aggregates into an entangled network of wormlike micelles. (1)H NMR and fluorescence spectroscopy demonstrate the formation of inclusion complexes between ChEO10 and methylated CDs, consistent with the demicellization observed. Instead, HEBCD forms a weak complex with ChEO10, while no complex is detected with SULFBCD. This shows that inclusion complex formation is not the determinant event leading to micellar growth. HEBCD:ChEO10 complex, which coexists with the aggregated surfactant, could act as a cosurfactant with a different headgroup area. For SULFBCD, intermolecular interactions via the external surface of the CD may be more relevant.
我们报告了天然环糊精（α-、β-和γ-）及其选定衍生物对非离子表面活性剂聚氧乙烯胆固醇醚（ChEO10）及其与三甘醇单十二烷基醚（C12EO3）混合物自组装的调节作用，它们可形成蠕虫状胶束。环糊精（CDs）通常通过与表面活性剂的主客体相互作用诱导胶束解体；相反，我们表明特定的CDs会产生一种建设性作用，导致凝胶形成，而且广泛提及的主客体相互作用可能不是缔合的唯一关键因素。当添加到ChEO10和C12EO3的蠕虫状胶束中时，天然β-环糊精、2-羟乙基-β-环糊精（HEBCD）和β-环糊精的硫酸化钠盐（SULFBCD）会使粘弹性大幅增加，而甲基化环糊精会使胶束破裂，导致粘度丧失，并且所研究的其他环糊精（天然α-和γ-环糊精以及羟丙基化环糊精）显示出较弱的相互作用。最值得注意的是，向纯ChEO10溶液（低粘度、小椭球形胶束的牛顿流体）中添加HEBCD或SULFBCD会诱导形成透明凝胶。小角中子散射、动态光散射和冷冻透射电子显微镜的结合表明，两种环糊精都会促使ChEO10聚集体伸长成为蠕虫状胶束的缠结网络。核磁共振氢谱（1H NMR）和荧光光谱表明ChEO10与甲基化环糊精之间形成了包合物，这与观察到的胶束解体一致。相反，HEBCD与ChEO10形成弱复合物，而未检测到SULFBCD与ChEO10形成复合物。这表明包合物的形成不是导致胶束生长的决定性事件。与聚集的表面活性剂共存的HEBCD:ChEO10复合物可能作为具有不同头基面积的共表面活性剂起作用。对于SULFBCD，通过环糊精外表面的分子间相互作用可能更重要。
