Preparation And Characterization Of Chemical Modification Of Chtiosan And Its Biological Application

Chitosan is an environmental friendly natural macromolecule and one of the most important and partially deacetylated derivatives obtained from chitin which is the second most abundant natural polysaccharide only next to cellulose in the world.Due to its biocompatibility, biodegradability,antibacterial and wound-healing activity and nontoxic property,chitosan is currently receiving a great deal of interest for biomedical and pharmaceutical application such as wound dressing,drug carrier and tissue engineered scaffolds and so on.However,chitosan is frequently limited by its insoluble nature in both water and current organic solvents because of its rigid crystalline structure and intra- and/or intermolecular hydrogen bonding which limited its application in the field of biomedical materials.In order to improve water and organic solubility for the further application of chitosan in biomedical materials fields,the water-soluble and organic-soluble chitosan derivatives were prepared by the Michael addition reaction and acylation reaction,respectively.Then,these derivatives were used to prepare biomedical application such as non-woven fabrics/nanofibers and tissue engineered scaffolds by electrospinning and blend solution-casting method techniques.The main contents and conclusions are described as follows.1.Water-soluble Hydroxyethylacryl-chitosan(HEA-CS) with different degrees of substitution from 0.18 to 1.2 was prepared by Michael addition reaction of chitosan and hydroxyethylacrylate. Hydroxyethylacryl-chitosan exhibited excellent solubility in distilled water.The thermal stability of hydroxyethylacryl-chitosan was lower than that of chitosan.Hydroxyethylacryl-chitosan showed strong lysozyme degradation and the degradation of hydroxyethylacryl-chitosan at the initial time depended on its molecular weight.The antimicrobial activity of hydroxyethylacryl-chitosan was low.This derivatiation procedure would be useful for the novel chemical modification to prepare water-soluble and biodegradable chitosan derivatives.2.The biocompatible blend films of HEA-CS/PVA were prepared by solution casting.The TS and the elongation increased with an increase content of PVA.The water contract angle of the blend film was low owing to the hydrophilic groups and the hydrophilic ability of the HEA-CS was higher than PVA.The surface morphologies of the freeze-dried blend films showed small pores and some interconnectivity. The blend film was thermally-stable owing to cross-linking with glutaraldehyde.The water swelling properties analysis indicated that HEA-CS in the blends promoted the water absorption owing to its porous structure.The antimicrobial ability of the blend films was decreased,but still had antimicrobial ability.Indirect cytotoxicity assessment of the blend films with human bone sarcoma cell(SW1353) indicated that the biomaterials were non-toxic and did not release substances harmful to living cells.3.The acylated chitosan with different degree of substitution from 1.8 to 3.8 were prepared by reaction of chitosan and stearoyl chloride in the mixed organic solutions.The acylated chitosan exhibited an excellent solubility in organic solvents at 25℃such as acetone,pyridine,benzene and dichloromethane.The thermal stability of acylated chitosan was lower than that of chitosan and the thermal stability of acylated chitosan decreased with increase of DS.The acylated chitosan had different crystallinity compared to that of chitosan for the long chain reside structure.This procedure could be a facile chemical modification method to prepare organic-soluble,and it could extent the application scope of chitosan.4.Biocompatible carboxyethyl organic soluble chitosan(O-CS)/ Polyhydroxybutyrate(PHB) fibers were successfully prepared by electrospinning.This part investigated the effects of polymer composition, electrospun voltage and electrospun distance on the fiber formation, morphology and the diameter distribution of blend fibers.Additionally, potential use of the electrospun fibers for wound dressing was studied by examining its cytotoxicity and cellular compatibility.The results showed that the fibers were hydrophobic.Indirect cytotoxicity assessment of the fiber mats indicated that the O-CS/PHB electrospun mat was nontoxic to L929 cell.Cell culture results showed that fibrous mats were well in promoting the cell attachment and proliferation.This novel electrospun matrix would be used as potential wound dressing for skin regeneration.5.Ultrafine and porous composite fibers were successfully fabricated by electrospinning of organic soluble chitosan(O-CS)/Poly ethylene oxide(PEO).The WCA data demonstrated that the fibers membranes performed a quite hydrophobic character.The special morphology of neck and porous structure was observed experimentally during electrospinning.The neck and porous structure was got and decided by the competition between the phase separation and the fast evaporation rate of chloroform.6.Ultrafine electrospun fibers of Chitosan/Poly(vinylalcohol) /Poly(vinylpyrrolidone)(CS/PVA/PVP) were prepared via electrospinning. The effects of the concentration of PVA,PVP and the electrospinning voltage on the morphology of ultrafine fibers were investigated by SEM. The morphology and diameter distributions of ultrafine fibers were affected by the factors.The rough surface fibers could be obtained after etching with CHCl₃ and it could be used as Biology tissue engineering.