Hydrogel, supramolecular

In a follow-up study, Dankers et al. extended the UPy-precursor toolkit to linear polymers containing UPy moieties in the main chain [156]. The authors studied the rheological behavior of these materials, reported on their intrarenal behavior and tissue response, and proposed possible therapeutic applications. In another seminal work, Meijer and coworkers developed UPy-based dual-fiber networks as a synthetic analogue to fiber formation in the cytoskeleton [157]. For this purpose, mixtures of mono- and bifunctional polymers were used, which a priori form fibers in water gelation could be achieved by decreasing the pH from 12 to 3. 

Recently, Song and coworkers reported a very simple new method for fabricating tough hydrogels that are physically cross-linked by cooperative hydrogen 

In contrast to the few examples of synthetic polymers that can be transiently cross-linked by hydrogen bonding, there is a huge variety of biopolymers that form supramolecular gels via hydrogen bonding. The most important representatives are polysaccharides such as cellulose [159, 160], starch [161], agarose [162, 163], 

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Zhang Y, Gu FTW, Yang ZM et al (2003) Supramolecular hydrogels respond to ligand-receptor interaction. J Am Chem Soc 125 13680-13681... 

Yang Z, Xu B. Supramolecular hydrogels based on biofunctional nanofibers of self-assembled small molecules. J Mater Chem 2007 17 2385-2393. 

Matsumoto S, Yamaguchi S, Ueno S, Komatsu H, Ikeda M, Ishizuka K, Iko Y, Tabata KV, Aoki H, Ito S, Noji H, Hamachi I (2008) Photo gel-sol/sol-gel transition and its patterning of a supramolecular hydrogel as stimuli-responsive. Biomaterials 14 3977-3986... 

Yang Z, Ma M, Xu B (2009) Using matrix metalloprotease-9 (MMP-9) to trigger supramolecular hydrogelation. Soft Matter 5 2546-2548... 

Yang ZM, Liang GL, Xu B (2007) Enzymatic control of the self-assembly of small molecules a new way to generate supramolecular hydrogels. Soft Matter 3 515-520... 

Gao Y, Kuang Y, Guo ZE, Guo Z, Krauss IJ, Xu B (2009) Enzyme-instructed self-assembly confers nanofibers and a supramolecular hydrogel of taxol derivative. J Am Chem Soc 131 13576-13577... 

Yang ZM, Liang GL, Ma ML, Gao Y, Xu B (2007) In vitro and in vivo enzymatic formation of supramolecular hydrogels based on self-assembled nanofibers of a beta-amino acid derivative. Small 3 558-562... 

Schnepp ZAC, Gonzalez-McQuire R, Mann S (2006) Hybrid biocomposites based on calcium phosphate mineralization of self-assembled supramolecular hydrogels. Adv Mater 18(14) 1869-1872... 

Wang QG, Yang ZM, Wang L, Ma ML, Xu B (2007) D-glucosamine-based supramolecular hydrogels to improve wound healing. Chem Commun 1032-1034... 

A supramolecular hydrogel underwent a reversible gel-sol transformation that was formed by adding 9,10-dimethoxy-2-anthracenesulfonic acid to an aqueous dispersion of a cationic amphiphile, (I), as was previously prepared by the author [1]. The gel had a network with a bilayer-membrane and a nanofiber... 

Supramolecular Hydrogels as Injectable Drug Delivery Systems. 96... 

Fig. 6 a-c The synthesis of PEO-PHB-PEO triblock copolymer a, and the schematic illustrations of the proposed structures of a-CD-PEO-PHB-PEO inclusion complex b, and a-CD-PEO-PHB-PEO supramolecular hydrogel c [71]... 

Fig. 7 The synthesis route for PEO-grafted dextran a and the schematic illustration of proposed structure of supramolecular hydrogel by inclusion complexation between PEO-grafted dextran and a-CD b [77]...

Fig. 9 Proposed structure of the supramolecular hydrogel formed between a-CD and Pluronic copolymer in the presence of well-dispersed single-walled carbon nanotubes (SWNTs) [80]...

Fig. 14 Injectable drug delivery system based on supramolecular hydrogels formed by a-CD and PEO [50]...

Hydrogels formed by PEO block copolymers have previously been proposed as sustained release matrix [85,86], The a-CD-PEO hydrogel delivery system differs in that the gelation relies on the formation of a polymer inclusion complex induced by the PEO-threaded CDs. The properties of the supramolecular hydrogel can be fine-tuned with the composition, molecular weight and chemical structure of the polymer or copolymers. 

Table 4 a-CD-PEO-PHB-PEO supramolecular hydrogel formulations used for in vitro con-trolled release studies [71] ... 

The advances in the studies on the inclusion complexes of CDs threading onto polymer chains have led to interesting development of supramolecular hydrogels with many different molecular and supramolecular structures. Both physical and chemical hydrogels of many different types were developed based on the CD-based polypseudorotaxanes and polyrotaxanes. 

Physical hydrogels were formed induced by self-assembled water-insoluble and crystalline polypseudorotaxane domains which act as physical crosslinking points. Such physical hydrogels include the polypseudorotaxane systems of a-CD threading on PEO or its copolymers, a-CD threaded on PEI, PL, or their copolymers, and even 3-CD or y-CD threaded PPO or PEI copolymers. The thermo-reversible and thixotropic properties of these supramolecular hydrogels have inspired their applications as injectable drug delivery systems. Physical hydrogels induced by physical interaction of threaded CD molecules in polyrotaxanes were also developed. 

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