Wang Meina, Wu Chunxian, Tang Yongqiang, Fan Yaxun, Han Yuchun, Wang Yilin
Key Laboratory of Colloid and Interface Science, Beijing National Laboratory for Molecular Sciences (BNLMS), Institute of Chemistry, Chinese Academy of Sciences, Beijing 100190, China.
Soft Matter. 2014 May 21;10(19):3432-40. doi: 10.1039/c4sm00086b. Epub 2014 Mar 19.
Interactions of trianionic curcumin (Cur(3-)) with a series of cationic surfactants, monomeric surfactant dodecyl trimethylammonium bromide (DTAB), dimeric surfactant hexamethylene-1,6-bis(dodecyldimethylammonium bromide) (12-6-12) and trimeric surfactant tri(dodecyldimethylammonioacetoxy)diethyltriamine trichloride (DTAD), have been investigated in aqueous solution of pH 13.0. Surface tension and spectral measurements indicate that the cationic surfactants display a similar surfactant concentration dependent interaction process with Cur(3-), involving three interaction stages. At first the three cationic surfactants electrostatically bind on Cur(3-) to form the surfactant-Cur(3-) complex. Then the bound and unbound cationic surfactants with Cur(3-) aggregate into surfactant-Cur(3-) mixed micelles through hydrophobic interactions above the critical micelle concentration of the surfactants (CMCC) in the presence of Cur(3-). Finally excess unbound surfactants self-assemble into micelles like those without Cur(3-). For all the three surfactants, the addition of Cur(3-) only decreases the critical micelle concentration of 12-6-12 but does not affect the critical micelle concentration of DTAB and DTAD. As the oligomeric degree of surfactants increases, the intermolecular interaction of the cationic surfactants with Cur(3-) increases and the surfactant amount needed for Cur(3-) encapsulation decreases. Compared with 12-6-12, either the weaker interaction of DTAB with Cur(3-) or stronger interaction of DTAD with Cur(3-) limits the stability or solubility of Cur(3-) in surfactant micelles. Therefore, gemini surfactant 12-6-12 is the best choice to effectively suppress Cur(3-) degradation at very low concentrations. Isothermal titration microcalorimetry, surface tension and (1)H NMR results reveal that 12-6-12 and Cur(3-) form a (12-6-12)2-Cur(3-) complex and start to form micelles at extremely decreased concentrations, where either 12-6-12 or Cur(3-) works as a bridge linkage and the resultant structure exhibits the characteristics of oligomeric surfactants.
在pH为13.0的水溶液中，研究了三阴离子姜黄素（Cur(3-)）与一系列阳离子表面活性剂的相互作用，这些阳离子表面活性剂包括单体表面活性剂十二烷基三甲基溴化铵（DTAB）、二聚表面活性剂六亚甲基-1,6-双（十二烷基二甲基溴化铵）（12-6-12）和三聚表面活性剂三（十二烷基二甲基铵乙酰氧基）二乙三胺三氯化物（DTAD）。表面张力和光谱测量表明，阳离子表面活性剂与Cur(3-)呈现出相似的依赖表面活性剂浓度的相互作用过程，包括三个相互作用阶段。首先，三种阳离子表面活性剂通过静电作用结合在Cur(3-)上，形成表面活性剂-Cur(3-)复合物。然后，在Cur(3-)存在下，结合和未结合Cur(3-)的阳离子表面活性剂在高于表面活性剂临界胶束浓度（CMCC）时通过疏水相互作用聚集形成表面活性剂-Cur(3-)混合胶束。最后，过量的未结合表面活性剂自组装成类似于没有Cur(3-)时的胶束。对于所有三种表面活性剂，Cur(3-)的加入仅降低了12-6-12的临界胶束浓度，但不影响DTAB和DTAD的临界胶束浓度。随着表面活性剂低聚度的增加，阳离子表面活性剂与Cur(3-)的分子间相互作用增强，包裹Cur(3-)所需的表面活性剂用量减少。与12-6-12相比，DTAB与Cur(3-)较弱的相互作用或DTAD与Cur(3-)较强的相互作用限制了Cur(3-)在表面活性剂胶束中的稳定性或溶解性。因此，双子表面活性剂12-6-12是在极低浓度下有效抑制Cur(3-)降解的最佳选择。等温滴定量热法、表面张力和（1）H NMR结果表明，12-6-12和Cur(3-)形成了（12-6-12）2-Cur(3-)复合物，并在极低浓度下开始形成胶束，其中12-6-12或Cur(3-)作为桥连键，所得结构表现出低聚表面活性剂的特征。
