Utilization as Molecular Container of Layered Double Hydroxides for Vitamins

为了开发生物相容性和健康支持材料，我们研究了层状双氢氧化物（LDH）作为“分子容器”的应用。本论文以Mg-Al、Mg-Fe和Zn-Al三种水滑石为主体氢氧化物层，研究了维生素C（L-抗坏血酸）和维生素A酸（视黄酸）在三种水滑石中的插层行为，以及客体维生素在水滑石中的稳定性和复合材料中维生素的释放。用共沉淀法制备的水滑石中维生素C只插层在Mg-Al和Zn-Al水滑石中，而重构法制备的水滑石中维生素C只插层在Mg-Al和Mg-Fe水滑石中。在每种情况下的插层等温线，并在所有的数据进行了很好的处理Freundlich吸附方程。此外，维生素A酸也插层在Mg-Al LDH中。另一方面，存在两种类型的维生素C，即，还原型和氧化型，只有前者具有还原和生理功能。在对所得维生素/LDH复合物进行白色光照射处理或热处理后，发现复合物中还原型维生素C的量是相同条件下裸复合物中还原型维生素C的量的约两倍。然后，通过与碳酸根离子的阴离子交换，从复合材料中释放出82 ~ 97%的维生素C。另外，维生素A酸也稳定在镁铝LDH的层间，易于通过阴离子交换释放出来，因此LDH可以作为维生素的“分子容器”。

For the development of biocompatible and health supporting materials, we have studied on the utilization of layered double hydroxide (LDH) as ‘Molecular container'. In this study, the intercalation of vitamin C (L-ascorbic acid) and vitamin A acid (retinoic acid) into tree kinds of LDH was investigated, as well as the stability of these guest vitamins in LDH and the release of vitamins from the resulting composites.First, Mg-Al,Mg-Fe and Zn-Al LDHs were adopteted as host hydroxide layers. It was found the vitamin C was intercalated only in Mg-Al and Mg-Fe LDHs by the reconstruction method and only in Mg-Al and Zn-Al LDHs by the coprecipitation method. The intercalation isotherms were obtained in each cases and all the data was well-treated by the Freundlich adsorption equation. Moreover, vitamin A acid was also intercalated in Mg-Al LDH.On the other hand, there is two types of vitamin C, i.e.,reduced type and oxidized type, and only the former demonstrates the reducing and physiological functions. After the white light irradiation treatment or heat treatment of the resulting vitamin/LDH composites, the amount of reduced type vitamin C in the composite was found to be about two times compared to that of the naked one in the same condition. Then, 82〜97% vitamin C was released from the composites by the anion exchange with carbonate ion. In addition, vitamin A acid was also stabilized in the interlayer of Mg-Al LDH and easily released by the same anion exchange.In conclusion, LDH can be used as ‘molecular container' for vitamins.