Zhi Fan

Formation and characterization of pseudo-polyrotaxanes based on poly(p-dioxanone) and cyclodextrins

Novel pseudo-polyrotaxanes (PPRs) consisting of poly(p-dioxanone) (PPDO) and cyclodextrins (CDs) were obtained via heat-cool (H-C) cycles. The optimum preparation condition for achieving the highest yield was investigated, which was selected as follow: 3 times H-C cycles in 72 h of PPDO and CDs dissolved in DMF at 60 °C. The PPRs were further characterized by using wide-angle X-ray diffraction (WAXD), NMR, FT-IR, and thermogravimetric analysis (TGA). It was found that PPDO could be wrapped by CDs units. Compare to the single PPDO chain, the PPRs have better thermal stability. Moreover, the hydrophilicity of PPRs is also enhanced significantly determined by the water static contact angle tests. In addition, hydrolytic degradation experiments showed that the PPRs had unique degradation behaviors. The construction of the PPRs based on the PPDO and CDs would further expand the application of PPDO as biomaterials.

Protein Imprinted with Cyclodextrin Pseudo polyrotaxanes as Pseudo-supports

Abstract Protein molecularly imprinted polymer (MIPs) was prepared with cyclodextrin pseudo-polyrotaxanes (CD-PPRs) as pseudo-supports, acrylamide as the monomer and N,N -methylene bisacrylamide as the cross-linker. Firstly, CD-PPRs were obtained with γ-cyclodextrin as hosts and poly(vinyl alcohol) as guests. Then CD-PPRs were modified with acryloyl chloride. Subsequently, the cp-MIP was prepared in the presence of the modified CD-PPRs (CD-PPRs-Ac) and metal ions with bovine serum albumin (BSA) as the template. The MIPs adsorption amount to the BSA template increased initially and then decreased with the increase of CD-PPRs. It was found that the adsorption capacity of MIPs reached maximum value when the ratio of CD-PPRs-Ac to AM was about 0.55. The adsorption maximum reached to 5.16 mg g −1 under the Cu 2+ conditions. Finally, the imprinted polymer was used to purify the template from the protein mixtures containing four (BSA, ovalbumin, soybean trypsine inhibitor and lysozyme) different proteins to evaluate the adsorption specificity of MIPs. The experiments showed that the recognition specificity was improved significantly and the adsorption capacity increases by 6 times with the introduction of CD-PPRs.

Self-assembly behavior of tail-to-tail superstructure formed by mono-6-O-(4-carbamoylmethoxy-benzoyl)-β-cyclodextrin in solution and the solid state.

A novel mono-modified β-cyclodextrin (β-CD) consisting of 4-carbamoylmethoxy-benzoyl unit at the primary side was synthesized and its self-assembly behavior was determined by X-ray crystallography and NMR spectroscopy. The crystal structure shows a Yin-Yang-like packing mode, in which the modified β-CD exhibits a channel superstructure formed by a tail-to-tail dimer as the repeating motif with the substituted group embedded within the hydrophobic cavity of the facing β-CD. The geometry of the substituted group is determined by the inclusion of the cavity and is further stabilized by two intermolecular hydrogen bonds between the carbonyl O atom and phenyl group. Furthermore, NMR ROESY investigation indicates that the self-assembly behavior of the substituted group within the β-CD cavity is retained in aqueous solution, and the effective binding constant Ka was calculated to be 1330 M(-1) by means of (1)H NMR titration according to iterative determination.

Self-assembly Behavior of Interlocked Helical Supramolecule of Cyclodextrin Modified by 2-Furanmethanethiol

The mono-modified β-cyclodextrin, mono-[6-S-6-(2-methylfuran)]-β-cyclodextrin, was synthesized by the substituting 2-furanmethanethiol for toluenesulfonyl group at the primary rim of β-cyclodextrin. Its self-assembly behavior was measured in both solution and the solid state by X-ray crystallography and H NMR spectroscopy. In the crystal structure, the complex, C47H106O51S, crystallizes in the orthorhombic space group P212121. The furan group is located above the primary rim of β-cyclodextrin and stretches slantwise along the side wall of β-cyclodextrin with the dihedral angle of 104.4° between furan ring and the plane of glycosidic oxygen atoms O(4) of β-cyclodextrin. The furan group is inserted deeply into the hydrophobic cavity of the adjacent β-cyclodextrin from the second hydroxyl rim and makes an angle of 67.6° with the O(4) atoms plane of the adjacent β-cyclodextrin. The dihedral angle of the O(4) atoms plane between the adjacent β-cyclodextrin is 38.4°. The consequence is the formation of an interlocked helical columnar superstructure formed by the self-assembly of the complex molecules in which the modified cyclodextrins are stacked along a two-fold screw axis parallel to the a crystal axis. Thus each molecule behaves both a host and a guest molecule. And the position and orientation of the furan ring within the cyclodextrin cavity is determined by host guest interactions which include the van der Waals contacts and hydrogen bonds between the furan ring and cyclodextrin. The interlocked helical column is stabilized by the hydrogen bonds formed between the primary and secondary hydroxyl groups of the adjacent cyclodextrin or through intervening water molecules. Furthermore, ROESY data indicate that the furan ring is included in the cyclodextrin cavity, which is in accordance with the conformation of the solid state structure. H NMR concentration dependent studies show that the complex molecule forms a dimer at concentrations of >10 mol•L. And the effective binding constant K and the aggregation number n were calculated to be 450 mol•L and 1.9, respectively.