| Currently,bone tissue engineering is a relatively ideal strategy for repair of bone defects.The research and development of scaffold materials is very important in the field of bone tissue engineering for its excellent performances.Natural bone is an organic/inorganic nano-composite,in which hydroxyapatite nanocrystals and collagen are tightly integrated in a hierarchical structure over several length scales.We need to simulate natural bones based on the composition and structure if we want to get the ideal bone repair materials.Various natural polymer were recombined with nano-hydroxyapatite to prepare bone tissue engineering materials,which are similar with natural bone in terms of the composition and structure.Considering that the organism itself is a typical hydrogel system,regulating the morphology and size of inorganic particles in a hydrogel matrix will have a broad prospects.on the basis of a large number of literature investigation and previous investigation of our laboratory,two different kinds of natural polymer hydrogel were firstly chosen as organic templates to regulate the in situ synthesis of nano-hydroxyapatite particles,and two kinds of silk fibroin with different crystallinity have been introduced as a secondary template to regulate the morphology and size of inorganic particles,with the aim to improve the mechanical strength of materials.The synthesized materials with special structure and excellent properties were compared in detail;secondly,high strength organic/inorganic composites,in which inorganic nano-hydroxyapatite phase were in situ synthesized on the surface of hydrogels,were prepared by biomimetic mineralization method,The specific research contents are as follows:1.The homogeneous chitosan/hydroxyapatite(CS/HAp),chitosan-Bombyx mori silk fibroin/hydroxyapatite(CS-BMSF/HAp),and chitosan-Antheraea yamamai silk fibroin/hydroxyapatite(CS-AYSF/HAp)composites were prepared by a facile in situ precipitation method.We focused on the comparison of these three composites on mechanical strength and biocompatibility in this part.The nucleation and growth of nano-hydroxyapatite were regulated by introducing two kinds of silk fibroin with different crystallinity.The results showed that this system have not only regulated the shape and size of nanoparticles,but also enhanced the compressive modulus of the composites,and promoted the proliferation behavior of MC3T3-E1 osteoblast cells on the materials.The results indicated that CS-AYSF/HAp composite may be an ideal material for bone tissue engineering.2.Under the inspiration of the first part,we have also introduced Bombyx mori silk fibroin(BMSF)and Antheraea yamamai silk fibroin(AYSF)into the bacterial cellulose/hydroxyapatite(BC/HAP)composite respectively.The composites all have good biocompatibility.The introduction of silk fibroin has significantly improved the mechanical strength of the composites,and we also found that the AYSF with high crystallinity,plays a decisive role in improving the mechanical strength of the composites because of the ?-sheet structure,the tripeptide sequence of AYSF is beneficial to the adhesion and proliferation of cells.The formation of dual-network like structure,which caused by the fact that BMSF peptide chain was not thoroughly broken by lithium bromide,has greatly improved the compressive strength of the BC-BMSF/HAp hydrogel.In addition,the scaffold platform we have prepared can be manufactured into 3D scaffold in any form,by stacking or some special methods like curling,folding and so on.In other words,this kind of interconnected porous structure may benefit the cellular ingrowth when used as bone tissue engineering scaffolds.It suggested that compared with BC-BMSF/HAp,the BC-AYSF/HAp composite was more appropriate as an ideal bone scaffold platform or biomedical membrane to be used in the future.3.On the basis of the previous two chapters,we have constructed a high stable dual-network bone scaffold platform with strontium ions sustained release capability.The formation of double network has significantly improved the mechanical strength of the composites.The introduction of strontium ions can better promote bone formation.The inorganic phase film can effectively reduce the degradation rate of gelatin,and also play an auxiliary role in the slow release of strontium ions.The previous works have not only laid a solid foundation on solving the problem of mismatch between porosity and mechanical strength,but also provided the theoretical support for the application of these composites in the field of bone tissue engineering. |
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