Supramolecular Co-assembly Of Two Types Of Hydrogelator And Hydroxypropyl-beta-cyclodextrin

Typical native cyclodextrins are composed of six, seven or eight glucose units and aredenoted-cyclodextrin, β-cyclodextrin and γ-cyclodextrin, respectively. Thedoughnut-shaped structure of CDs is characterized by the presence of glucose residues inC1conformation with hydroxyl groups arranged around the outer rim. Because of thechair conformer of the glucopyranose units, CD’s shape is not a perfect cylinder, but atruncated cone. For the exits of the hydroxyl, the exterior edge of CDs is hydrophilic, andthe inner cavity is hydrophobic. Therefore, different kinds of molecules could beconcluded into the cavity of CDs. Most of the studied of CDs are about-cyclodextrin,and it can form (pseudo-)polyrotaxanes with long-chain molecules. However, studiesaboutβ-cyclodextrin are much less than-cyclodextrin. In this article, two kinds ofgelators containing benzene ring coassemble with hydroxypropyl-beta-cyclodextrinforming supramolecular gel were studied in detail respectively.First, a kind of gelator composed by1,2,4,5-Benzenetetracarboxylic acid and4-Hydroxypyridine (1:2)(HB21for short)was chosen to assemble with HP-β-CD in waterand made the sample of HB21/HP-β-CD/water. Several different test methods were takento characterize the morphology, temperature of phase transition, structure and so on of thesample, such as FE-SEM, DSC, FT-IR, XRD. What’s more, pyrene was added into the gelas fluorescence probe in order to cherify the gels fluorescence. The result of the HB21molecular can enter into the cavity of hydroxypropyl-beta-cyclodextrin and forming cagelike structures are gained.Then, N-(9-Fluorenylmethoxycarbonyl)-L-phenylalanine（Fmoc-L-phenylalanine）waschosen to assemble with HP-β-CD in PBS buffer solution and made the sample of HB21/HP-β-CD/PBS hydrogel. By analyzing the atlas of XRD, the result of theFmoc-L-phenylalanine molecular can enter into the cavity ofhydroxypropyl-beta-cyclodextrin and forming cage like structures are gained. What’s more, Gaussian03program was used to calculate the minimum energy configurations ofN-(9-Fluorenylmethoxycarbonyl)-L-phenylalanine. This is the preparation job forspeculating the co-assembly of Fmoc-Phe-OH and HP-beta-CD.