Design,Preparation And Properties Of Calcium Phosphate Silicate Based Composites Materials For Tendon To Bone Healing

Due to the complex transitional structure of tendon to bone insertion,the mechanical properties of regeneration tissue of tendon to bone insertion after surgery is difficult to well match the original tissue,which is easily to cause retear.Nowadays,more and more materials are devoted to improve the tendon to bone healing.Considering the unique structure and complicated composition of the tendon to bone site,in this dissertation,bioactive calcium calcium phosphate ceramics and biocompatible polymers have been applied to develope composite materials for tendon to bone repair.The calcium silicon phosphate phase composites were prepared by electron beam evaporation,hot pressing and casting techniques.Furthermore,the physical and chemical properties of prepared composites were characterized,and the cytocompatibility of the materials was also investigated.The formation of tendon to bone interface and the mechanical performace of new tissue were evaluated through animal tests in vivo.The relationship between biological properties and composite component was deeply studied.The main results obtained are described as follows:(1)Preparation of PLGA/CPS nanolayer composite film by electron beam evaporation and its propertiesA novel bioactive and nano-scale calcium phosphate silicate ceramic(CPS)layer was coated on the surface of PLGA films using electron beam evaporation(EBE)technique.The SEM results revealed that the thickness of Ca-P-Si coating increased with a longer modification time and XPS further indicated that the Ca-P-Si coating exhibited a gradient distribution in the PLGA surface.It was also found that the CPS-modified samples exhibited a significantly improved hydrophilicity and a more negative zeta potential.Cell culture results showed that the CPS-modified samples were beneficial to the attachment and proliferation of rBMSCs and NIH3T3 cells.CPS-modified samples also showed an improved osteogenic activity.(2)Preparation of PLLA/CPS composite film by melt-pressing technique and its propertiesPLLA/CPS composite films were produced by a simple and environment-friendly melt-pressing technique.The results showed PLLA/CPS composite films owned a decreased water contact angle,rougher and more positive charge surfaces than PLLA sample.With an increase of CPS content,the adhesion and proliferation of rat bone marrow mesenchymal stem cells(rBMSCs)on composite films were improved and the expression of ALP activity,extracellular matrix mineralization and collagen secretion were enhanced.The in vivo results also revealed that the PLLA/CPS composite film had good biocompatibility and biodegradability.12 weeks after surgery,a well engineered tendon to bone interface was formed in the PLLA/CPS composite film case.(3)Construction of PCL/CPS gradient composite film by tape casting and its propertiesThe PCL/CPS gradient composite films were prepared by a simple tape casting method.The results showed that with an increase of CPS content,the surface roughness and the water contact angle of each component film decreased.In vitro experiments showed that each component film promoted the adhesion and proliferation of MC3T3 and NIH3T3 cells and co-cultured the two cells with the increase of calcium silicate phosphate content.In vivo animal experiments showed that the gradient composite film can promote the formation of the transition zone of the tendon to bone interface and enhance the mechanical performance of new bone tissue.Heparin molecules were immobilized on the aminolyzed PCL surface to improve the cellular bioactivity for potential tendon repair.The results showed that heparin molecules could be effectively immobilized on the PCL surface through an aminolysis modification.PCL films exhibited a more negative surface after heparin immobilization.The existence of heparin enhanced the adsorption of proteins.Moreover,heparin immobilized PCL sample improved the attachment and proliferation of NIH3T3 and ATDC5 cells,also enhanced the secretion of collagen and glycosaminoglycans(4)Preparation of PCL/Sr-CPS composite film by tape casting and its propertiesStrontium-doped calcium phosphate silicate(Sr-CPS)powders were synthesized by sol-gel method.The Sr-doped calcium silicate phosphate below 5% can reach a relatively pure phase at 1300?,and the 10% Sr-doped calcium silicate powder had other impurities at 1300 ?.The PCL/strontium-doped calcium phosphate(Sr-CPS)composite film was prepared by a simple casting method.The amount of Ca ion released was proportional to the Ca content of PCL/Sr-CPS films,and the release of Sr ions was the largest in P/Sr-10 sample.In vitro cell experiments showed that PCL/Sr-CPS composite films can promote early adhesion and proliferation of cells related to tendon to bone healing,and the existence of Sr stimulate the osteogenic differentiation and the collagen secretion of cells.