| The attenuation of mechanic intensity of chitosan rods is rapid due to their high water penetrating rate and large amount of water adsorption, which limits their practical application as internal fixation of bone frature. In this thesis , chitosan/hydroxyapatite composite layers and bio-ester coatings were prepared for surface hydroprobiztion of chitosan rods, and the biological safety of chitosan rod and bio-ester were evaluated.1. Based on the in-situ hybridization and the intermittently precipitation, the CS/HA composite layers were prepared by a novel and simple two-step method. XRD and ED AX were used to determine component of the composite. The mechanical properties of the composite were evaluated, and the effects of time in coagulator A and alternate soaking cycles on bending strength of CS/HA composite rod were discussed.2. Many terrestrial plants and animals are water-repellent due to hydrophobic surface components in connection with a microscopic roughness. Leaves that are water-repellent for only a short period of time have only slightly convex epidermal cells and often have a less dense wax layer. Bio-ester solution coating was adopted as the method of surface hydrophobic modification of chitosan rod. Then the water-repellent effect was characterized by contact angle and water absorption rate. Soaked in SBF three months, mechanical properties attenuation showed that the surface modification mimicking microstructure of the plant leaf is a method of feasibility to improve water-repellent property of the chitosan rod.3. To evaluate the biological safety of chitosan rod and bio-ester, the cytotoxicity test, hemolysis test and eye sensitivity test were investigated with standard method. Bio-ester was no cytotoxicity and almost no obvious hemolysis. Chitosan rods were no cytotoxicity and no sensitivity. The chitosan rods andbio-ester have excellent biocompatibility and biological safety for the clinical application in the future.
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