Chitosan, derivatives hydrogels

Besides enzymatic degradation, the biodegradation behavior of chitosan derivatives hydrogels can also be evaluated by soil burial, microbial attack, and so on. The CM-chitin and CM-chitosan hydrogels before and after keeping for 10 weeks in soil is found to become smaller, revealing that... 

Nagasawa, N., W acedil sikiewicz, J. M., Seko, N. et al. 2006. Metal adsorption of chitin/chitosan derivatives hydrogels crosslinked with irradiation. JAEA-Review 042 52-55. 

Fig. 10 (a) Molecular structure of a water-soluble and crosslinkable chitosan derivative (CML) obtained by grafting methacrylic acid and lactic acid onto the pendant amine groups of chitosan. The structure does not represent the real ratio between each monomer unit, (b) Illustration of the chitosan hydrogel network linked by alkyl chains, which are formed via C=C polymerization [116]... 

Yang, J., Chen, J., Pan, D., Wan, Y, and Wang, Z., pH-sensitive interpenetrating network hydrogels based on chitosan derivatives and alginate for oral drug delivery, Carbohvdr. Polvm.. 92 (01)(2013), 719-725. 

Generally, chitosan and chitosan derivatives have been extensively used for protein drug deliveiy due to their amphiphilic characters. After various crosslinking, the formed hydrogels can be used to load and release proteins by tuning external stimulus factors. 

Masci, G., Husu, L, Murtas, S., Piozzi, A., and Crescenzi, V. 2003. Physical hydrogels of poly(vinyl alcohol) with different syndiotacticity prepared in the presence of lactosilated chitosan derivatives. Macromol. Biosci. 3 455-461. 

The cross-linking behavior of chitosan derivatives can be evalnated by calcnlating some important valnes related to the formation of hydrogels, snch as D, according to Charlesby-Rosiak eqnation (Olejniczak et al. 1991) ... 

Chitosan derivatives, charged or uncharged, can form three-dimensional networks under cross-linking (Wasikiewicz et al. 2006, Yoshii et al. 2003, Zhao and Mitomo 2009, Zhao et al. 2003). Some typical properties of these hydrogel materials formed from chitosan derivatives such as CM-chitosan and DHP-chitosan are selected to be introduced here. 

Hydrogels show a marvelous prospect for the procedure of metal-ions recovery from dilute solutions (Peter 1995, Varma et al. 2004). Recently, the adsorption of natural organic pollutants (such as humic acids) from aqueous solution using chitosan adsorbents has attracted intensive attention in environment and health fields (Ngah and Musa 1998, Wu et al. 2002, Yan and Bai 2005). Adsorbents, derived from a nature polymer, are required for environment-conscious technologies. The adsorptions of metal ions and humic acid from aqueous solutions onto radiation cross-linked chitosan derivatives were introduced here. 

A, 0-carboxymethyl chitosan (N,0-CC) is a chitosan derivative that has carboxymethyl substituents at some of both the amine and the 6-hydroxyl sites of its glucosamine units. It can be easily prepared using chitosan, sodium hydroxide, and isopropanol with chloroacetic acid [65]. N,0-CC as a wound dressing can stimulate the extracellular lysozyme activity of fibroblasts and considerably promote the proliferation of skin fibroblasts. N,0-CC is also used in the development of various functional hydrogels, including superporous or pH-sensitive hydrogels, which are used for protein drug delivery [66-69]. 

Sakai S, Yamada Y, Zenke T et al (2009) Novel chitosan derivative soluble at neutral pH and in-situ gellable via peroxidase-catalyzed enzymatic reaction. J Mater Chem 19 230-235 136. Jin R, Moreita Teixeira LS, Dijkstra PJ et al (2009) Injectable chitosan-based hydrogels for cartilage tissue engineering. Biomaterials 30 2544—2551... 

Nguyen, T., et al., 2014. Enzyme-mediated in situ preparation of biocompatible hydrogel composites from chitosan derivative and biphasic calcium phosphate nanoparticles for bone regeneration. Adv. Nat. Sci. Nanosci. Nanotechnol. 5 (1), 015012. Available at http //m. iopscience.iop.org/article/10.1088/2043-6262/5/l/015012/pdf (accessed 05.01.16). 

Redox-initiated polymerization using ammonium persulfate (APS)/N,N,N, N -tetramethylethylenediamine (TEMED) or APS/ascorbic acid has been used to encapsulate cells in poly(ethylene glycol) (PEG), oligo(PEG fumarate) (OPE), poly (lactide-co-ethylene oxide-co-fumarate) (PLEOF), chitosan derivatives, or carboxybetaine hydrogels [6-11]. In these systems, an increase of initiator concentration led a decrease in the gelling time, however, it also affected the cell viability. Therefore, low cytotoxic free radical polymerization is needed to use this method for biomedical applications. 

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