Medical applications hydrogel properties

This is undoubtedly one of the most promising medical applications for chitin and chitosan. The adhesive properties of chitosan, together with its antifungal and hactericidal charactCT, and its pameahOity to oxygen, are very important properties associated with the treatment of wounds and burns. Diffa-ent draivatives of chitin and chitosan have been patented for this purpose in the form of membranes, woven fibres, hydrogels, etc. Some of these formulations have been released on the market, like Beschitin in Japan (based on chitin) or HemCon in USA (based on chitosan). 

M.T. Nistor, C. Vasile, A.P. Chiriac, A. Rusu, C. Zgardan, L.E. Nita, and I. Neamtu, Hybrid sensitive hydrogels for medical applications, in M. Bercea, eds.. Polymer Materials with Smart Properties, Nova Science, chap. 3, pp. 67-90, 2013. 

Pietrucha, K. and Banas M. (2009). Diffusive properties of hybrid collagen derivative hydrogels for medical applications, www.hybridmate-rialsconference.com. 

This chapter focuses on two subjects related to the field of mechanically stimulated reactions (1) chemical and photochemical CTOss-linking of HA in aqueous solutions and (2) advanced methods of solid-phase polysaccharide modification. From these processes, the cross-linked hyaluronic hydrogels acquire a number of valuable properties that significantly extend the range of their medical applications. 

Polyurethane hydrogels are widely used in soft contact lenses, controlled release devices, semipermeable membranes and hydrophilic coatings (66). The properties of polyurethane hydrogels can be varied by variation of their components, such as the polyols, diisocyanate, chain extender, or cross-linker (67-69). Because of the excellent mechanical and physical properties, polyurethanes are widely used in medical applications such as coating for medical devices for preventing protein adsorption (70, 71). 

Moreover, novel redox-responsive polycationic hydrogels of AAf-diethylacrylamide (DEAAm) and 2-(dimethylamino)ethyl methacrylate (DMAEMA) were successfully synthesized by cross-linking reactions via quaternary ammonium compounds with a disulfide. The ability of the polymer netwoik to enclose and release substances by reductive cleavage or oxidative formation of disulfide bonds was shown exemplarily using different dyes. The redox-responsive character was proven by oscillatory rheological measurements and different material properties of polycationic polymer discs were also investigated. Because of its polycationic structure, this polymeric system could be a promising compound for complexation of DNA-like substances. Its ability for selective release in reductive environments, like tumor tissues, could possibly be used in medical applications or in chemotherapy [162]. 

Similar to the chemical modifications applied to alginate, chitosan can be treated with chloro-acetic acid, ethylene oxide, and propylene oxide to obtain sodium car-boxymethyl chitosan, hydroxyethyl chitosan, and hydroxypropyl chitosan, respectively. These derivatives are highly absorbent and can be used for the production of superabsorbent fibers for medical applications. In addition to enhanced absorption properties, it is known that carboxymethyl chitosan possesses unique wound-healing properties whereby the application of foams, hydrogels, or nonwoven dressings can effectively promote the healing of chronic ulcerative wounds. 

Similarly to the phospholipid polymers, the MPC polymers show excellent biocompatibility and blood compatibility [43—48]. These properties are based on the bioinert character of the MPC polymers, i.e., inhibition of specific interaction with biomolecules [49, 50]. Recently, the MPC polymers have been applied to various medical and pharmaceutical applications [44-47, 51-55]. The crosslinked MPC polymers provide good hydrogels and they have been used in the manufacture of soft contact lenses. We have applied the MPC polymer hydrogel as a cell-encapsulation matrix due to its excellent cytocompatibility. At the same time, to prepare a spontaneously forming reversible hydrogel, we focused on the reversible covalent bonding formed between phenylboronic acid and polyol in an aqueous system. 

Polyethylene oxide has been shown to be an excellent mucoadhesive polymer. Low levels of polyethylene oxide are effective thickeners, although alcohol is usually added to water-based formulations to provide improved viscosity stability see Table II. Polyethylene oxide films demonstrate good lubricity when wet. This property has been utilized in the development of coatings for medical devices. Polyethylene oxide can be radiation crosslinked in solution to produce a hydrogel that can be used in wound care applications. 

The primary focus of this entry has been to provide a basic understanding of the field of hydrophilic polymers and their uses. These materials have a range of applications both in the bulk and as thin films. For example, hydrogel membranes are used as inhibitors of postsurgi-cal adhesion formation and also as coatings. Dispensing these polymers onto the surface of medical devices can confer desirable surface properties that the substrate... 

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