Preparation Of A Functional Bone Repairing Material By Biomimetic Mineralization

Po1y(3-hydroxybutyrate-co-3-hydroxyvalerate)(PHBV) is one of bone-repairing materials, it is synthesized by microbial fermentation and has good performance in biocompatible and biodegradable behavior. Although PHBV has many advantages as a bone-repairing material, it still can’t meet the clinical demands perfectly, so it is necessary to improve the material performance through a variety of methods.Pearl powder has the ability to induce bone formation for the reason that it contains bone morphogenetic protein and this kind of protein can stumulate human osteoblasts. Pearl powder was used to prepare PHBV/pearl powder composite scaffolds. Biomimetic mineralization in simulated body fluids was employed to generate hydroxyapatite(HA). When composite scaffold was immersed in simulated body fluids for biomimetic mineralization, the pearl powder in it would have effect on HA deposition. PHBV / pearl powder composite scaffold contain antitumor drugs were prepared and we discussed the drug release characteristic of this drug delivery system. The inhibition of this drug-loading scaffold on tumour cells was proved using MTT method. The main work is as follows:In chapter 2, porous PHBV films were prepared with the help of Sodium Chloride as the pore forming agent. The biomimetic mineralization ability and biological performance of the films were evaluated. It was found that the porous films show a better biological activity than films without porous structure. In the same mineralization conditions the films contained pearl powder could induce HA growth quickly than films without pearl powder, indicating that pearl powder could accelerate HA deposition. The amount of HA becomes higher with increasing content of pearl powder in films, the better biological activity was found when pearl powder was added. FTIR and XRD study revealed that the structure of HA was weak crystal type, which is a kind of bone apatite.In chapter 3, we successfully fabricated PHBV/pearl composite scaffolds by electrostatic spinning. It was found that the incorporation of pearl powder is in favor of spinning of PHBV. Mineralization ability of these composite scaffolds was greatly enhanced due to naturally non-toxic pearl powder, which acts as crystal nucleus for HA particle deposition. The amount increase of HA on scaffolds is proportional to the content of pearl powder. The introduction of pearl powder can also improve the biocompatible activity of PHBV scaffolds and promote the cells proliferation. Therefore, the prepared PHBV/pearl composite scaffolds would be a promising candidate as an osteoconductive composite material for bone repairing.In chapter 4, hydrochloric acid doxorubicin(DOX) as an anticancer drug was added in the composite scaffolds and DOX/PHBV and DOX/PHBV/Pearl scaffolds were prepared by electrostatic spinning. The drug release characteristics of the composite scaffolds were discussed. When immersed in phosphate buffer solution(PBS) the two kinds of scaffolds showed a fast release at first and then releasing rate becomes slow; and the two kinds of scaffolds exhibited good sustained releasing effect. Moreover pearl powder shows the function to control drug release i.e., higher content of pearl powder lead to a much more releasing amount. Biomimetic mineralization experiments indicated that HA could be deposited on both DOX/PHBV and DOX/PHBV/Pearl scaffold. Both DOX/PHBV and DOX/PHBV/Pearl scaffolds show anticancer function to MG-63 cell, the more pearl powder in scaffolds, the better anticancer activity was found. Therefore, these electrospun DOX/PHBV and DOX/PHBV/Pearl scaffolds have obvious advantages and potential applications in the field of anti-tumor drug controlled release.