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  • 1
    Electronic Resource
    Electronic Resource
    Supramolecular Approach to Gene Delivery (2008)
    s.l. ; Stafa-Zurich, Switzerland
    Advances in science and technology Vol. 57 (Sept. 2008), p. 144-147 
    Details
    ISSN: 1662-0356
    Source: Scientific.Net: Materials Science & Technology / Trans Tech Publications Archiv 1984-2008
    Topics: Natural Sciences in General , Technology
    Notes: The most definite feature in polyrotaxanes, in which many cyclic compounds are threadedonto a linear polymeric chains capped with bulky end-groups, is the mobility of cyclic compounds:these cyclic compounds may rotate and/or slide along the polymeric chain. Our previous studies haveclarified that the mobility of ligands linked to the cyclic compounds is closely related to enhancingmultivalent interaction with biological systems. This concept is now exploiting more practicalapplications for drug delivery such as gene delivery. We have designed biocleavable polyrotaxanesthat have a necklace-like structure between many dimethylaminoethylcarbamoyl-α-cyclodextrins(DMAE-α-CDs) and a disulfide (SS)-introduced poly(ethylene glycol) (PEG) chain. Thepolyrotaxanes were found to show sufficient cleavage of S-S linkages under reducible condition,which led to triggering pDNA release via the dissociation of the non-covalent linkages betweenDMAE-α-CDs and the PEG chain. The polyrotaxanes were finally clarified to exhibit greattransfection activity as well as non cytotoxicity
    Type of Medium: Electronic Resource
    URL: http://www.tib-hannover.de/fulltexts/2011/0528/01/42/transtech_doi~10.4028%252Fwww.scientific.net%252FAST.57.144.pdf
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  • 2
    Electronic Resource
    Electronic Resource
    Polyrotaxanes: Challenge to Multivalent Binding with Biological Receptors on Cell Surfaces (2003)
    s.l. ; Stafa-Zurich, Switzerland
    Materials science forum Vol. 426-432 (Aug. 2003), p. 3243-3248 
    Details
    ISSN: 1662-9752
    Source: Scientific.Net: Materials Science & Technology / Trans Tech Publications Archiv 1984-2008
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Type of Medium: Electronic Resource
    URL: http://www.tib-hannover.de/fulltexts/2011/0528/02/07/transtech_doi~10.4028%252Fwww.scientific.net%252FMSF.426-432.3243.pdf
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  • 3
    Electronic Resource
    Electronic Resource
    Feasibility study of hydrolyzable polyrotaxanes aiming at implantable materials (2000)
    Springer
    Journal of artificial organs 3 (2000), S. 136-142 
    Details
    ISSN: 1619-0904
    Keywords: Hydrolyzable polyrotaxane ; Supramolecular dissociation ; Hydrogel ; Tissue engineering
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine , Technology
    Notes: Abstract Hydrolyzable polyrotaxanes, in which many α-cyclodextrins (α-CD) are threaded onto a poly(ethylene glycol) (PEG) chain capped withl-phenylalanine via ester linkages, were synthesized to estimate the supramolecular dissociation via terminal ester hydrolysis. The polyrotaxane showed unique thermoresistant properties due to the supramolecular structure. The supramolecular structure was completely dissociated by terminal ester hydrolysis. PEG hydrogels cross-linked with the polyrotaxane were prepared as new candidate implantable materials for tissue engineering. It is suggested that controlling the rate of terminal ester hydrolysis and the following supramolecular dissociation may dominate the disappearance of the hydrogel. These findings will be of great importance for designing a scaffold based on the primary structure of the polyrotaxane that shows dual characteristics of excellent mechanical properties and perfect disappearance from an implanted site.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02479980
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  • 4
    Electronic Resource
    Electronic Resource
    Blood-contacting properties of polypropylene surfaces (1998)
    Springer
    Journal of artificial organs 1 (1998), S. 4-9 
    Details
    ISSN: 1619-0904
    Keywords: Polypropylene ; Blood-contacting properties ; Crystalline-amorphous microstructure ; Protein ; Platelets
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine , Technology
    Notes: Abstract Blood-contacting properties of polypropylene varied with changes in crystalline-amorphous microstructure such as the crystallinity and the degree of orientation. The results from our evaluation of surface adhesiveness using polymeric glue and water structure which was sorbed into the surfaces indicate that variations in the microstructure may cause differences in macromolecular entanglement with the glue and hydrophobic interaction at the surfaces. Therefore, the prevention of these interactions may help to attain better blood-contacting properties.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01340445
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  • 5
    Electronic Resource
    Electronic Resource
    Effects of surface crystallinity on dynamic mechanical properties of compression-molded polypropene sheets (1996)
    Weinheim : Wiley-Blackwell
    Angewandte Makromolekulare Chemie 243 (1996), S. 87-98 
    Details
    ISSN: 0003-3146
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Description / Table of Contents: Die dynamisch-mechanischen Eigenschaften von preßgeformten Polypropen-Probekörpern mit gleicher Massekristallinität aber unterschiedlicher Oberflächenkristallinität, wurden untersucht. Die Temperatur der α-Relaxation sinkt mit abnehmender Oberflächenkristallinität. Eine zwischen den Temperaturen der α- und β-Relaxation auftretende Schulter wird der Oberflächenschicht zugeschrieben. Das Takayanagi-Modell wurde auf die experimentellen Ergebnisse angewendet und deutet auf die unterschiedliche Kontinuität der amorphen Phase zwischen der Oberflächenschicht und der Masse hin.
    Notes: Dynamic mechanical properties are measured for a series of compression-molded polypropene sheets having the same bulk crystallinity but different surface crystallinity. The temperature of the α-dispersion was shifted to lower temperatures with lowering the surface crystallinities of the sheets. A shoulder peak, which is ascribed to the surface layer, appeared between the α- and β-dispersion for the sheets. In addition, the application of the Takayanagi model to the experimental results suggests the difference in the continuity of the amorphous phase between the surface layer and the bulk.
    Additional Material: 8 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/apmc.1996.052430108
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  • 6
    Electronic Resource
    Electronic Resource
    Double-stimuli-responsive degradable hydrogels: interpenetrating polymer networks consisting of gelatin and dextran with different phase separation (1996)
    Weinheim : Wiley-Blackwell
    Macromolecular Rapid Communications 17 (1996), S. 313-318 
    Details
    ISSN: 1022-1336
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: Biodegradable interpenetrating polymer network (IPN)-structured hydrogels consisting of gelatin (Gtn) and dextran (Dex) were prepared by sequential crosslinking reactions of Gtn and methacryloylated Dex. Phase separation of these hydrogels is dominated by preparation conditions, i.e., above or below the sol-gel transition temperature (Ttrans) of Gtn. Enzymatic degradation by either α-chymotrypsin or dextranase is hindered for the IPN-structured hydrogel prepared below Ttrans whereas this hydrogel is perfectly degradable in the presence of both enzymes. Such a specific feature of enzymatic degradation was not observed for the hydrogel prepared above Ttrans. These results suggest that double-stimuli-responsive degradation of IPN-structured hydrogels is related to their phase separation.
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/marc.1996.030170505
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  • 7
    Electronic Resource
    Electronic Resource
    Thermally switchable polyrotaxane as a model of stimuli-responsive supramolecules for nano-scale devices (1996)
    Weinheim : Wiley-Blackwell
    Macromolecular Rapid Communications 17 (1996), S. 509-515 
    Details
    ISSN: 1022-1336
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: A polyrotaxane consisting of many β-cyclodextrins (β-CDs) and a triblock copolymer of poly(ethylene glycol) (PEG) and poly(propylene glycol) (PPG) capped with bulky end-groups was synthesized as a model of stimuli-responsive supramolecules for nanoscale devices. The polyrotaxane was reversibly soluble-insoluble in water in response to temperature. This was achieved through the assembled and dispersed states of β-CDs along the block copolymer. It is considered that intermolecular hydrogen bondings of β-CDs, as well as the PEG segment length of the copoloymer, are predominant factors for regulating such thermally switchable behavior of the polyrotaxane.
    Additional Material: 6 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/marc.1996.030170803
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  • 8
    Electronic Resource
    Electronic Resource
    Supramolecular dissociation of biodegradable polyrotaxanes by enzymatic terminal hydrolysis (1998)
    Weinheim : Wiley-Blackwell
    Macromolecular Chemistry and Physics 199 (1998), S. 2311-2320 
    Details
    ISSN: 1022-1352
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: Supramolecular dissociation of biodegradable polyrotaxanes via terminal hydrolysis by an enzyme (papain) in vitro was investigated in relation to their solution properties. The polyrotaxanes were synthesized by the introduction of L-phenylalanine (L-Phe) at both ends of an inclusion complex consisting of α-cyclodextrins (α-CDs) and amino-terminated poly(ethylene glycol) (PEG) via peptide linkages, followed by the hydroxypropylation of α-CDs. From static and dynamic light scattering studies, it was clarified that the polyrotaxanes form a loosely packed association but L-Phe-terminated PEGs form a tightly packed association. Further, the polyrotaxanes were found to maintain their rod-like structures in physiological conditions. In vitro degradation experiments using papain revealed that the terminal hydrolysis of the polyrotaxanes is completed and accompanied by the release of hydroxypropylated α-CDs, and this behavior is not affected by the association number of the polyrotaxanes. On the other hand, the terminal hydrolysis of L-Phe-terminated PEG is limited under similar conditions. From these results, the complete dissociation of the polyrotaxanes by hydrolysis is considered to be due to the loosely packed association, presumably related to the rod-like structure.
    Additional Material: 10 Ill.
    Type of Medium: Electronic Resource
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  • 9
    Electronic Resource
    Electronic Resource
    Modulated degradation of dextran hydrogels grafted with poly(N-isopropylacrylamide-co-N,N-dimethylacrylamide) in response to temperature (1998)
    Weinheim : Wiley-Blackwell
    Macromolecular Chemistry and Physics 199 (1998), S. 2613-2618 
    Details
    ISSN: 1022-1352
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: Dextran hydrogels grafted with poly(N-isopropylacrylamide-co-N,N-dimethylacrylamide) were prepared, and their enzymatic degradation was examined at different temperatures. Although swelling ratios for the hydrogels are constant in a wide range of temperature, there is a drop of transmittance of the hydrogels in the swollen state in relation to the lower critical solution temperature of poly(N-isopropylacrylamide-co-N,N-dimethylacrylamide). Temperature-dependent enzymatic degradation was observed in these hydrogels to depend on the molecular weight of the grafts. The degradability of the hydrogel with shorter grafts is independent of temperature. In contrast, the degradability of the hydrogel with longer grafts increases with increasing temperature. Such a modulated degradation of hydrogels is considered to be due to a change in the entanglement between the grafted chain and dextran network by the hydration-dehydration behavior of the grafts.
    Additional Material: 9 Ill.
    Type of Medium: Electronic Resource
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  • 10
    Electronic Resource
    Electronic Resource
    Modulated degradation of hydrogels with thermo-responsive network in relation to their swelling behavior (1998)
    Weinheim : Wiley-Blackwell
    Macromolecular Chemistry and Physics 199 (1998), S. 705-709 
    Details
    ISSN: 1022-1352
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: Hydrogels consisting of poly(N-isopropylacrylamide-co-N,N-dimethylacrylamide-co-butyl methacrylate) and a novel biodegradable cross-linker were synthesized with different concentrations of ammonium peroxodisulfate (APS) as a free radical initiator by photo-induced radical reaction. The swelling ratio of the hydrogels decreased rapidly in proportion to temperature. In vitro enzymatic degradation of the hydrogels was examined in buffer solution containing papain at different temperatures. The enzymatic degradation of the hydrogel prepared with higher APS concentration was observed to proceed at 30°C, however, the hydrogel was not degraded above 35°C. Such an on-mloff switching degradation in response to temperature was not observed for hydrogels prepared with lower APS concentration. It is considered that modulated degradation of hydrogels with a thermo-responsive network is achieved by controlling the cross-link density and eliminating the entanglement of polymeric main chains.
    Additional Material: 6 Ill.
    Type of Medium: Electronic Resource
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