Processing of Chitosan

Blends or composites were also prepared especially by Hirano in the same way as mentioned previously for chitin [63], Other systems were proposed in the literature and listed previously [1, 2], Some of them are described in detail, for example, chitosan/ polyamide 6 and chitosan/polyamide 66 [119,120], chitosan/cellulose using a common solvent [121,122], chitosan/poly(oxyethylene) (POE) [123], chitosan/polyvinylpyrrolidone (PVP), chitosan/polyvinyl alcohol (PVA) [123,124], chitosan/polycaprolactone [124-126], chitosan/ collagen [127], chitosan/PHB [128], and chitosan/cellulose fibres [129]. In some case, the polymers are crosslinked in the blends [130]. Hydrogels or films have been prepared by mixing chitosan solution with monomers, initiator and cross-linker followed by copolymerization [131,132]. 

Recently, reinforcement of chitosan film with carbon nanotubes was tested. This composite demonstrates a large increase in the tensile modulus with the incorporation of only 0.8% of multiwalled carbon nanotubes [133]. Many papers concern bio-inorganic composites, including hydroxyapatite, which increases the mechanical properties and mimics the nanostructure of bone [88, 134, 135]. 

Chitosan derivatives. Due to the chemical structure of chitosan, specific reactions can be performed on the amino group in C-2 position of the glucosamine unit, especially by reductive amination reaction. Also two -OH groups are available on C-3 and C-6 positions [1,2]. The more interesting is to test reactions on the C-2 position. Two different types of derivatives may be recognized (i) derivatives obtained by chemical modification and introduction of different substituents, (ii) grafted copolymers on C-2 position. 

The physical cross-linking in these amphiphilic polymers is based on hydrophobic interactions between side chains which counterbalances the electrostatic repulsions between cationic chitosan chains in acidic condition [154], 

Electrostatic complex. Chitosan being a polyelectrolyte is able to form interesting electrostatic complexes with other oppositely charged macromolecules to give hydrogels. The properties of these complex materials depend on the polymer concentration, temperature, pH, ionic concentration, and so on. Few examples are given in the following. 

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This chapter focuses and reviews on the characteristics and biomedical application of chitosan and collagen from marine products and advantages and disadvantages of regeneration medicine. The understanding of the production processes of chitosan and collagen and the conformation of these biomaterials are indispensable for promoting the theoretical and practical availability. The initial inflammatory reactions associated with chitosan application to... 

Silica, silver, bioactive glass, heparin, and CaSiOs have been incorporated into the electrodeposition process of chitosan and HA to try and improve performance of composite coatings for biomedical implants that interface with bone tissue [116, 119, 134, 139, 149]. While the electrodeposition methods and mechanical and adhesion strength of the coatings are commonly reported in these studies, little biological data has been gathered on the response of cells or tissues to these composite coatings. 

Fig. 2 Slurry in the stainless-steel holding tank of the Microfluidizer after continuous high shear fluid processing of chitosan powder for mechanical disassembly into nanofibrils. Scaleable results are produced for pilot and production purposes...

Advances in Processing of Chitosan-Based Systems and Clinical Relevance... 

The characterization and processing of chitosan were then described. Solubility in acidic media is a valuable property, extending processing methods and the domains of application. The polysaccharide may be processed as Abre, Aim, sponge, bead, gel or soluAon. Due to the presence of free -NH2 groups, speciAc modiAcaAons can be performed on the C-2 position of the D-glucosamine unit. 

Scheruhn et al. (1999) reported that treating coffee drinks with chitosan increased the pH level and decreased the acid content of the beverage due to the acid-binding properties of chitosan with coffee. The efficacy of this treatment depends on the concentration, source, and processing of chitosan as well as on the acid content of the drinks (Scheruhn et al. 1999). 

As far as ultrasonication is concerned for the preparation and processing of chitosan nanoparticles for drug delivery applications, high-intensity ultrasonication is not recommended [156]. 

Agglomeration of chitosan microspheres was used as a technique for fabrication of bone scaffolds by a complex process of chitosan spheres extrusion, scaffold formation by compression followed by the spheres agglomeration and bonding with crosslinking agent (STPP, sodium tripolyphosphate) [117]. 

Chitin with a degree of deacetylation greater than 75% is known as chitosan [58]. The versatility of chitosan as an industrial material stems from the presence of a high proportion of free reactive amino groups. The processing of chitosan is a relatively unexplored field, compared to the more conventional materials, and the majority of applications are still at the development stage [59]. 

One important characteristic related with chemical structure, which affects directly the processability of chitosan is the solubility. Chitosan is insoluble in water and alkaline media. This is due to its rigid and compact crystalline structure and strong intra- and intermolecular hydrogen bonding. However, chitosan is soluble only in few dilute acid solutions (Vroman and Tighzert, 2009]. In fact, solubility is a very difficult parameter to control, and it is related to the degree of acetylation, the ionic concentration, the pH, the nature of the acid used for protonation, and the distribution... 

The preparation process of chitosan magnetic microspheres can be divided into two steps. First, the Fe304 particles were prepared by coprecipitating Fe and Fe ions by ammonia solution and treating under hydrothermal conditions. Second, the Fe304 particles and chitosan acidic solutions were mixed to form the microspheres. 

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