Department of Food Quality and Safety, Zhejiang Gongshang University, Hangzhou, Zhejiang 310035, P. R. China.
J Phys Chem B. 2012 Oct 11;116(40):12372-80. doi: 10.1021/jp3071184. Epub 2012 Oct 2.
The real-time energetics involved in the structural change of a zwitterionic vitamin-derived bolaamphiphiles (DDO) vesicles, which were induced by conventional surfactants, such as hexadecyltrimethylammonium bromide (CTAB), sodium dodecyl sulfate (SDS), and Triton X-100 (TX100), was characterized by isothermal titration calorimetry (ITC). Interactions of both CTAB and SDS with DDO were accompanied with considerable heat release whereas the interaction energetics between TX-100 and the vesicles were small. However, the transition of DDO vesicles to micelles did occur upon the addition of all of the three surfactants. Fine inflection points were observed in heat flow enthalpograms, which indicated systematically the change of vesicle structure. By monitoring the interaction of CTAB with DDO, we found that heat release kept constant over a certain concentration range at higher temperatures. The repairing effect of heating was revealed and a reversible transition from micelles to vesicles of DDO was thus realized. Further encapsulation of fluorescein in DDO vesicles proved that the reversible vesicle-micelle transition was controllable. This research demonstrates that ITC combined with complementary analytical methods such as dynamic light scattering (DLS) and transmission electron microscopy (TEM) helps to get the real-time information of the structural changes of vesicles. It also shows that these synthetic novel bolaamphiphiles offer great promise for designing controllable release system.
采用等温滴定量热法（ITC）对由传统表面活性剂（如十六烷基三甲基溴化铵（CTAB）、十二烷基硫酸钠（SDS）和 Triton X-100（TX100））诱导的两性离子维生素衍生的 bolaamphiphiles（DDO）囊泡的结构变化中涉及的实时能量学进行了研究。CTAB 和 SDS 与 DDO 的相互作用伴随着相当大的热量释放，而 TX-100 与囊泡之间的相互作用能量很小。然而，当加入所有三种表面活性剂时，DDO 囊泡确实会向胶束转变。在热流焓图中观察到精细的拐点，这系统地表明了囊泡结构的变化。通过监测 CTAB 与 DDO 的相互作用，我们发现热量释放在较高温度下在一定浓度范围内保持恒定。加热的修复效果被揭示出来，从而实现了 DDO 从胶束到囊泡的可逆转变。进一步将荧光素封装在 DDO 囊泡中证明了这种可逆的囊泡-胶束转变是可控的。这项研究表明，ITC 结合动态光散射（DLS）和透射电子显微镜（TEM）等互补分析方法有助于获取囊泡结构变化的实时信息。它还表明，这些合成的新型 bolaamphiphiles 为设计可控释放系统提供了很大的希望。
