Polyrotaxanes, cyclodextrin-based

Due also to their controllable size, low cytotoxicity, and unique architecture, cyclodextrin-based polyrotaxanes and pseudopolyrotaxanes have been developed to encompass a broad range of diverse medical applications from erodable hydrogels to drug and gene delivery. A recent review about biomedical applications of cyclodextrin based polyrotaxanes have been reported by Loethen et al. [64],... 

Yui s group has investigated biodegradable polymers based on the cyclodextrin-based polyrotaxanes over the course of the last decade [128-139]. First, they prepared polyrotaxanes from a-cyclodextrin and PEG bisamine (Scheme 23) [128]. For example, l-phenylalanine was employed as an enzymatically hydrolyzable endcap. The in vitro degradation experiments using papain showed that a-cyclo dextrin was indeed released only when the terminal peptide linkages were hydrolyzed. They have prepared various kinds of polyrotaxanes based on cyclodextrin and have demonstrated that these polyrotaxanes are effective as drug delivery systems. 

Harada et al. constructed a molecular tube out of a-cyclodextrin-based polyrotaxane (Scheme 25) [156]. The polyrotaxane was synthesized from a... 

Cyclodextrin-Based Polyrotaxanes 1113 Akira Harada and Hiroyasu Yamaguchi... 

Drug-Conjugated Biodegradable Cyclodextrin-Based Polyrotaxane... 

Cyclodextrin Based Polyrotaxanes and Polyseudorotaxanes for Gene Delivery. 237... 

Imaging/Labeling Applications Cellulose cyclodextrin-based polyrotaxanes histamine/ histidine lysozymes nucleic acids polyamines proteins " poly(dimethylsiloxane) (PDMS) oligomers ... 

Biological/Medical Applications Characterizing cyclodextrin-based polyrotaxanes detecting nucleic acids, - polyamines immobilizing proteins " probing lysozyme in human serum as a substrate for measuring polymerases activity," recombinases activity," topoisomerases activity" ... 

Supermolecular interlocked macromolecules have been paid much attention as candidates of smart materials. Polyrotaxane (PRX) is a typical example. PEG/ cyclodextrin (CD)-based polyrotaxane was firstly reported by Harada and coworkers by attachment of stoppers to pseudopolyrotaxane (pPRX) consisting of a PEG and CDs [263]. Subsequently, many CD-based PRXs have been designed and prepared as smart materials such as biomaterials, light-harvesting antennae, insulating polymers, stimuli-responsive molecular shuttles etc. [264—268]. 

Obtaining polyrotaxanes by the statistical method through polymerization of various monomers in the presence of macrocycles was attempted by Maciejewski who investigated the thermal radical copolymerization of vinylidene chbride, methyl methacrylate (MMA), acrylonitrile (AN), acrylamide, and thdr mixtures with ace-tonaphtylene in aqueous and dimethylformamide solutions in the presence of p-cyclodextrin or of its acylic derivative. All these attempts failed, however. Only, when copolymerization was initiated by y-radiation with an exposure dose of 5 Mrad, did some of the above-listed monomers form polymers exhibiting optical activity. However, the rotation of the initial p-cyclodextrin was 162°, while that of the obtained products only l°-6°. Such a small polarization plane rotation angle could result only from an insignificant amount of macrocycles in the synthesized compounds. Therefore, for the purpose of a more successful synthesis of cyclodextrin-based rotaxanes, a number of researchers tried to introduce elements of directionality into... 

Polyrotaxanes, in which many cyclic molecules are mechanically interlocked onto a polymeric chain, have been synthesized using macrocyclic compounds such as cyclodextrins, crown ethers and blue boxes. Synthesis of pillar[5]arene-based polyrotaxanes consisting of cationic polymers, such as viologen polymer, is relatively easy because pillar[5]arene forms stable host-guest complexes with cationic molecules (see details in Chapter 9) however, it is difficult to synthesize nonionic polymer-based polyrotaxanes. To synthesize nonionic polymer-based polyrotaxanes, we used a liquid... 

Polyrotaxanes have been prepared by threading multiple a-cyclodextrin units onto a bulky benzimidazole-based linear chain polymer with an aliphatic spacer where the cyclodextrin resides. The rotaxane forms as the cyclodextrin-bound precursor amine is polymerised. Compared to the polymer in the absence of the cyclodextrins, the glass transition temperature is raised by some 20 °C even though only ca. 16 % of the aliphatic spacers in the polymer are rotaxanated.28 A novel approach to polyrotaxanes involved the use of a metal ion such as Zn2+ to thread a phenanthroline-based macrocycle onto a thiophene-based complementary monomer. The resulting pseudorotaxane can then be electropolymerised and the Zn2+ ions removed to give a polyrotaxane, Scheme 14.5. The redox and conductivity properties of the polymer are very much dependent on whether a metal ion is bound or not.29... 

A fascinating self-assembly process is based on the spontaneous threading of cyclodextrins or crown ethers onto polyether polyamine" or polyurethane chains (Figure 5.30). The formed polyrotaxanes possess several cyclodextrin units which are trapped after appropriate capping of the ends. Polymerization of the threaded cyclodextrins and removal of the central thread then leads to molecular cyclodextrane tubules with an inner hydrophobic tunnel and a diameter of about 5 A. 

Yui s group has also developed stimuli-responsive polyrotaxane materials based on cyclodextrins in the last decade [140-155]. They synthesized polyrotaxanes, in which many / -cyclodextrins are threaded onto a triblock copolymer PEG-co-PPG-co-PEG and trapped with fluorescein (Scheme 24)... 

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