Developments of Chitosan as Functional Biomaterials

Chitin, next to cellulose, is the second most abundant polysaccharide in nature; it is widely found in the exoskeletons of crustacea and insects as well as in the cell walls of fungi and algae. Prepared by the N-deacetylation of chitin, chitosan is a semi-crystalline polysaccharide constituted by N-glucosamine and N-acetyl-glucosamine units, with an amount of N-glucosamine units exceeding 50%. Since chitosan is reported to have many promising properties, the aim of this thesis is to develop and magnify chitosan as practical biomaterial.
The first chapter reviewed researches done before; it is necessary to understand and have a full scope in the past and the trend of future.
In the second chapter, the preparation of chitosan of different molecular weight with acetic acid and the kinetics of acid-depolymerization were discussed. The structure identification of these depolymerized chitosan is performed and its preliminary blood compatibility was also investigated. Finally, the acid-depolymerization mechanism of chitosan is proposed.
In the third chapter, chitosan/γ-Poly(glutamic acid) PEC hydrogel, formed by ionic interactions, were fabricated based on several compositions by varying molar ratios of amine groups of chitosan to carboxylic acid groups of γ-PGA. Beside the physicochemical characteristics of these chitosan/γ-PGA PEC hydrogels, their physical behaviors and in vitro biological behaviors were also fully investigated.
In the fourth chapter, based on the previous chapter, the in vivo evaluation was conducted to develop chitosan/γ-PGA PECs as wound dressing materials.
The fifth chapter was designed to assess the in vivo epithelium tissue and muscle tissue response of chitosan/γ-PGA PECs using a rat model. We have examined several factors affecting the soft tissue response.
The sixth chapter was dedicated to develop the superabsorbent hydrogel as a good mimic for extracellular matrix. The hydrogel was composed of all nature poymer, fabricated by the amide bond formation, hoping to be a replacement of acrylate-based hydrogel.