| Natural bone is an ideal composite material which is perfectly organized by ordered collagen fibrils and highly oriented nano hydroxyapatite(HA) crystals. Its hierarchically organized natural structures and the amazing forming process provide a host of inspiration for the research of biomimetic material. In this thesis, the mixture of poly(3-hydroxybutyrate-co-3-hydroxyvalerate)(PHBV) and Poly(butanediol succinate)(PBS)(PHBV/PBS) as well as the blending of PHBV and pearl powders(PHBV/Pearl) were used as matrix separately to grow HA, so that HA/polymer composites were obtained. In addition, electrospinning was facilitated to prepare 3-dimensional PHBV scaffolds that were used to help initiate the growth of HA and analyse the morphology, structure and amounts of hydroxyapatite formed on the surface by biomimetic mineralization. Meanwhile, the biocompatibility and bioactivity of materials were fully evaluated. As a results, All the study provided the valuable data for the selection and application of bone tissue repair materials in the future.Biodegradable polymer blend films of PHBV/PBS were prepared by co-dissolving the two polyesters in chloroform and casting the mixture. Differential scanning calorimetry (DSC) and thermogravimetric analysis were used to investigate the thermal property and compatibility of PHBV/PBS blends as well as the mechanical properties. The results showed that though PHBV and PBS were incompatible, the mechanical properties of the certain ratio of PHBV/PBS were better than either PHBV or PBS. By adjusting different experiment parameters of alternative soaking process, such as pH values, temperatures, alternative cycles etc. The results indicted that the increase of interaction cycles, temperature and the PBS content as well as the pretreatment processing enhance the growth capabilities of HA. HA grew significantly at pH=7.4, while the lower and higher pH value could inhibit the total growth of HA. The obtained HA was confirmed by SEM and infrared analysis as B-HA which is quite similar to bonelike HA.PHBV/Pearl composites were prepared by adding nano pearl powders into PHBV, which was able to improve the mechanical properties and hydrophilicity of PHBV films. Besides, the existence of pearl powders on the surface of composites facilitated the growth capabilities of HA in a short period in SBF(simulated body fluid). The infrared analysis confirmed that the surface of composites was well covered by carbonate bearing apatites. The existence of pearl powders created more ideal conditions for the heterogeneous nucleation of HA, enhancing the activity of PHBV in SBF. Moreover, MG-63 cells could well attach and proliferate on the surface of PHBV/Pearl films and the activity of alkaline phosphatase(ALP) was enhanced with the increase content of pearl powders, which demonstrated the potential value of this composite as a kind of bone tissue repair material. By changing the ingredients of SBF, different morphologies of HA coatings could be observed. In addition, the unique rob-shaped carbonate (CaCO3) particles were synthesized by continuous bubbling CO2 gas into SBF, which suggested the possibility of mineralization of unstable CaCO3 in SBF.Considering the structural bionics and biomimetic synthesis, the porous PHBV scaffolds were fabricated by electrospinning. After soaking in SBF, the orientated growth of HA along fibers was obtained. Through effective pretreatment of scaffolds by soaking in CaCl2 and K2HPO4 solutions for 24 hours respectively. The results of assessing cell proliferation and the activity of ALP indicated that the coverage of HA was able to maintain the 3D structure and enhance the hydrophilicity, biocompatibility and bioactivity of PHBV scaffolds.The novelties of the study are as follows:the existence of nano pearl powders in PHBV/Pearl improved the mechanical properties of composites, enhanced the activity of mineralization of hydroxyapatite and the biocompatibility of PHBV. By precisely adjusting various parameters, the effects that influence mineralization of HA were investigated. Rod-shaped carbonate firstly was prepared by bubbling CO2 gas into SBF, which provided valuable data for the orientated mineralization of hydroxyapatite by unstable carbonate crystals. |
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