Preparation And Property Study Of Alginate/Peptide Fibers/Nano Hydroxyapatite For Injectable Bone Repairing Materials

An ideal bone repair material should have good biocompatibility,matching degradation,good bone induction,filling and shaping in the bone defect and easy operation.Injectable bone material complies with the demand of minimally invasive surgery and conducts in a non-invasive and minimally invasive way to repair individual bone defect,with little tissue damage,convenient operation,good biocompatibility,shaping to bone defect and other advantages,showing great prospects in clinical applications.In this study,inspired from the bone structure and function characteristics,a series of alginate/peptide nanofiber/nano hydroxyapatite based injectable composite hydrogel materials were designed,prepared and studied,and their application prospects for minimally invasive repairing of individual bone defect was explored either.In Chapter 1,an alginate/collagen/nano hydroxyapatite based injectable composite hydrogel was prepared by simulating bone structure and functional properties.By adjusting the proportion of each component and gel accelerator parameters,the physicochemical properties of the composite hydrogel,icluding gelation time,rheological property,microstructure and in vitro degradation etc.were systematically studied.It was found that the alginate/collagen/nano hydroxyapatite complex can be controlled within 10 to 40 minutes to form stable hydrogels.The composite hydrogels in different curing ratio all showed porous and connective structures.And the microstructures like collagen and n HA can be significantly distinguished.The mechanical strength of the composite hydrogel is obviously enhanced compared with pure sodium alginate hydrogel.Moreover,the composite hydrogel showed good degradation performance with dry state loss rate reached more than 70% in 9 weeks in SBF solution in vitro.In Chapter 2,the biocompatibility,in vivo biological safety and repair effect on skull defect of alginate/collagen/nano hydroxyapatite composite hydrogel were systematically studied.The proliferative activity and osteogenic differentiation ability of the composite hydrogel on osteoblast MC3T3-E1 were investigated.The tissue response to bone implantation,intradermal reaction,pyrogen reaction,skin irritation reaction,and the acute systemic toxicity were systematically studied in rabbits and mice.The mouse skull defect model was established and further planted with the composite hydrogel to investigate the repairing effect and regeneration of bone defect.It was found that the composite hydrogel showed low cytotoxicity to MC3T3-E1 cells and good trend for osteogenic differentiation.The composite hydrogel has good biocompatibility from the results,including no local tissue reaction for bone implantation,no skin reaction,mild skin irritation,mild thermal reaction,no acute systemic toxicity.After of implantation of skull defect for 8 weeks,a large number of new bone was formed and bone mineralization density increased significantly,showing good osteoinductive ability and application prospect.In Chapter 3,a temperature sensitive injectable in situ forming bone repairing material was prepared from the combination of temperature sensitive alginate compound,cell adhesion promoting peptide nanofibers and osteoinductive nano hydroxyapatite.By Simulating the structure and cell adhesion biological properties of collagen,the chimeric polypeptide composed of cell adhesion sequence(RGD)and ionic crosslinking sequence(EEE)was designed and used for self-assembly into nanofibers,to enhance the mechanical properties and biological functions of the composite hydrogels.The rheological mechanical properties of the poly N-isopropylacrylamide(PNIPAAm)modified alginate,the peptide self-assemblity and mechanism,and the gelation,morphology,mechanical properties,in vitro degradation of the composite hydrogel was systematically studied.It was found that the thermo-sensitive hydrogels showed good injectable gel time which can be controlled within 6-10 minutes.These hydrogels have porous and connected structure and micro/nano surface,with pore size up to tens of micrometers and hydroxyapatite uniformly dispersed in the organic matrix and internal surface.The hydrogels have good mechanical properties and good integrity,without breakdown.Moreover,the temperature sensitive composite hydrogels showed good degradation performance more than 3 months in vitro.In Chapter 4,the proliferation and differentiation of osteoblasts and in vivo biological safety of the temperature sensitive composite hydrogels were systematically studied.The effect of the temperature sensitive composite hydrogels on proliferation and differentiation of osteoblast MC3T3-E1 was investigated.The tissue response to bone implantation,intradermal reaction,pyrogen reaction,skin irritation reaction,and the acute systemic toxicity were systematically studied in rabbits and mice.It was found that the temperature sensitive composite hydrogels were favorable to the adhesion,proliferation and differentiation of osteoblast MC3T3-E1,showing good biocompatibility and osteoinductive properties.In vivo experiments recovered that the composite hydrogel can support a long-term implantation and keep intact without breakdown,with the degradation period over 3 months.More importantly,the temperature sensitive composite hydrogels have good biocompatibility,including no local tissue reaction for bone implantation,no skin reaction,mild skin irritation,no thermal reaction and no acute systemic toxicity,and good tendency to promote bone regeneration,showing great application prospect.