Hyaluronic acid-based derivatives

Hyaluronic acid is a linear polysaccharide formed from disaccharide units containing N-acetyl-D-glucosamine and glucuronic acid. Since it is present in almost all biological fluids and tissues, hyaluronic acid-based materials are very useful in biomedical applications. After cellulose, chitin is the second most abundant natural polysaccharide resource on earth. Chitin and its de-acetylated derivative chitosan are natural polymers composed of N-acetylglucosamine and glucosamine. Both chitin and chitosan have excellent properties such as biodegradability, biocompatibility, non-toxicity, hemostatic activity and antimicrobial activity. Chitin and its derivatives are widely used in various fields of medicine. 

Sannino A, Madaghiele M, Conversano F, Mele G, Maffezzoli A, Netti PA, Ambrosio L, Nicolais L (2004) Cellulose derivative-hyaluronic acid-based microporous hydrogels cross-linked through divinyl sulfone (DVS) to modulate equilibrium sorption capacity and network stability. Biomacromolecules 5 92-96... 

Hultin (77) has derived an expression for the enzymic depolymerization of hyaluronic acid based on Staudinger s (182) equation relating specific viscosity and molecular weight. This equation permits the calculation of a microunit for enzymic activity. The formula was applied to data published by Madinaveitia and Quibell (112) and Swyer and Emmens (183). The values obtained showed fairly good agreement for the higher substrate concentrations. 

Knowing that nitric oxide and hyaluronic acid both play an important role in the wound healing process, Di Meo et al. chose to combine the properties of both entities and synthesized new NO-donors based on hyaluronic acid derivatives exhibiting a controlled NO-release under physiological conditions (in vitro tests). These derivatives were fully characterized by and 13C NMR spectroscopy and their NO release monitored by means of UV spectrophotometric measurements.47... 

Chitosan-based nano- and microparticles are widely used for fabrication of controlled dmg release systems. Numerous studies have demonstrated that chitosan and its derivatives (A-trimethyl chitosan, mono-A-carboxymethyl chitosan, etc.) are effective and safe for absorption enhance to improve mucosal (nasal, peroral) delivery of hydrophylic macromolecules, such as peptide and protein dmgs as well as heparins [37,38]. This absorption enhancing effect of chitosan is caused by the opening of intercellular tight junctions, thereby favoring the paracellular transport of macro-molecular dmgs. Recently, a series of successful model chitosan-based polymer systems for mucosal dmg delivery have been reported. Thus, Lim et al. [39] have proposed novel polymer microparticles based on combination of hyaluronic acid and chitosan hydroglutamate... 

The natural materials are often derived from skin such as, for example, collagen, gelatin, fibrin, hyaluronic acid, chondroitin sulfate and also acellular dermis from cadaveric skin origin. But materials from other origins are also widely used, such as bacterial polyesters (Valappil et al., 2007), cellulose (Teeri et al., 2007), chitosan, alginate, dextran, etc. A lot of constructs based on natural products can be found in different forms such as membrane, plate, sheet, fiber, sponge, and hydrogel. 

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