Preparation And Characterization Of Bioactive Membrane For Guided Tissue Regeneration

The aim of this thesis is to prepare the chitosan(CS)/ hydroxyapatite(HA) composite membrane with good osteoinductivity for the biomedical application in guided tissue regeneration field. A novel alternate soaking process was developd to fabricate HA coating on the chitosan-based membrane. In addition, the porous structure was constructed on the chitosan-based membrane via electrospinning of CS/PVA/HA blends.1. Preparation and characterization of CS/HA composite membrane via alternatesoaking process.All the chitosan membranes which are treated with NaOH gelating agent and Na₅P₃O₁₀, Na₂SO₃ crosslinking agents have good performance on degradability, water aborsption and mechanical property that could satisfy the basic requirements of guided tissue regeneration, and the membrane treated with NaOH has better properties compared to other membranes. The HA coating was sucessfully fabricated by the novel alternate soaking process. TGA results indicated that HA content increased with increasing immersion cycles in calium and phosphate solutions, and the HA content achieved the saturated amout 8.8% after 4 immersion cycles. SEM images showed that a HA layer was deposited on one side of the chitosan membrane, the other side of that film is smooth. In addition, it was also revealed by the SEM images that the morphologies of HA gradually transformed from regular granule-shaped crystals to wide flat plate-shaped crystals with increasing immersion cycles. The mechanical test showed that with an increase in immersion cycles, the tensile strength of membrane reduced from 68.6MPa to 46.9 MPa. These results indicated that the crystal morphology, content, and mechanical performance of HA could be altered by changing immersion cycles so as to meet the requirements of guided tissue regeneration.2. Porous structure with good osteoinductivity coustructed by electrospun nanofibers on the surface of chitosan-based membraneIt was very difficult to fabricate pure chitsoan nanofiber when the molecular weight of chitosan was too high or too low. Various chitosan with different molecular weight could be achieved by adjusting the degradable time in the chitosan solution with hydrogen peroxide. The pure chitosan nanofiber with diameter ranged from 200 to 500nm was sucessfully prepared by electrospinning the solution(concentration: 8wt%, Molecular weight =102090, applied voltage: 40kV, tip to collector distance: 10cm, solvent: 90% concentrated acetic acid solution). The stuctuce and morphology of electrospun CS/PVA nanofibers with good biocompatibility and uniform diameter are ultrafine and smooth. In addition, after soaking in 5%NaOH methanol solution for 12h, the mat retained a significant degree of fibrous character ever after 3 days of immersion in water. Compared to the electrospun CS/PVA nanofibers, nanofibers which are electrospun from CS/HA/PVA have better morphology and smaller diameter. The FE-SEM showed that some HA nanoparticles disperse well in the solution, but the other aggregated in the solution. Due to these phenomenon, after electrospinning, some nanoparticles were filled in the chitosan-based nanofibers and some nanoparticles which aggregated in the solution were layed between the nanofibers or the on the surface of nanofibers. All these results indicated that the porous structure with good osteoinductivity based on electrospun CS/PVA biocomponent nanofibers filled with HA nanoparticles could be successfully constructed on the surface of chitosan-based membrane for guied tissue regeneration.