Polyrotaxane is a general term for supramolecules in which a linear polymer chain threads into the cavities of numerous cyclic molecules, and bulky sealing groups are introduced at both ends to prevent the cyclic molecules from dethreading. Therefore, although polyrotaxane is a high molecular weight compound, there are no covalent bonds between the numerous cyclic molecules and the linear polymer chain, and these molecules can be regarded as mechanically linked to each other. One of the cyclic molecules that have been used in polyrotaxane design over the past several decades is a cyclic oligosaccharide, popularly known as cyclodextrin.
In 1993, we began research to design biomaterials with new functions using a polyrotaxane skeleton composed of cyclodextrins, and have reported the emergence of many biomaterials with new functions. All of these functions are supported by the unique characteristics of polyrotaxanes, in which molecules are linked to each other by mechanical bonds, and we are proud to have demonstrated the breadth and depth of a new world that is completely different from that of conventional polymers, in which molecules are linked together by covalent bonds. In this article, we will focus on the following two areas of polyrotaxane research: (1) modulation of cellular functions by molecularly mobile polyrotaxane surfaces and (2) potential application of degradation-responsive polyrotaxane for the treatment of intractable metabolic diseases. ...and more
Cyclodextrins (CDs) are a class of cyclic oligosaccharides consisting of several α-(1,4)-linked D-glucopyranose units (Figure 1A). CDs composed of 6, 7, and 8 glucosidic units are called α-, β-, and γ-CDs, respectively, and have been used extensively. They have a sub-nanometer-sized cavity that can accommodate guest molecules of the appropriate size and shape. The inclusion ability of CD has been academically studied as a catalyst, sensor, etc., and has been widely utilized industrially in foods, cosmetics, and pharmaceuticals. On the other hand, CDs can regularly assemble intermolecularly through hydrogen bonding between hydroxyl groups on the upper and lower rims of their doughnut-shaped rings or through host-guest molecular interactions. Recently, much attention has been paid in the fields of supramolecular chemistry and materials science to studies on nano- and microstructures formed by the assembly of CDs5,6. This article reviews the preparation of supramolecular structures by using the regular assembly of CD molecules, and the morphological control of supramolecular structures. ...and more
Cyclodextrins (CDs), cyclic oligosaccharides, are water-soluble host molecules that can include various kinds of guest molecules utilized not only in basic research but also as food additives. CDs with oligo-glucose structure have interesting properties; however, CDs can be chemically modified and thereby acquire new functions. We are studying the artificial hemoglobin “hemoCD”, which consists of a per-O-methylated CD dimer and iron porphyrin (FeTPPS). In this article, I describe the strategy of hemoCD preparation and its medical applications. ...and more
Cyclodextrins (CDs) are cyclic oligomers of α-1,4-D-glucopyranoside. Because the central cavities of CDs can be used to encapsulate small molecules, cyclic hexamer to octamer (CD6–8) have been widely used. While CD-hundreds are known for large CDs, the synthesis of the only CD5 had been only one reported for small CDs. Smaller CDs, such as CD4 and CD3, have never been synthesized because their molecular sizes are too small for the pyranose ring to adopt a stable chair-type conformation. In this report, we describe the chemical synthesis of both CD4 and CD3. The development of a specific bridging group between the 3- and 6-oxygen positions (O-3 and O-6) of D-glucose led to the successful synthesis of these compounds. In other words, the adoption of this bridging group provides both the stereoselective glycosylation reaction and the supple conformation of the pyranose ring, which are required for the synthesis of CD4 and CD3. ...and more
