| The research on bone tissue replacement materials is one of the most attractive aspects of biomedical engineering. Materials for defect replacement and repairing process special functional requirements for mechanical properties for bone-bearing, biocompatibility, osteoconductivity and osteoinductivity. Therefore, the exploration of the bone replacement materials based on tissue engineering technology has become a heated topic in this field. Traditional bioceramic such as β-tricalcium phosphate(β-TCP) has a component simulated with bone minerals, and possesses a good biocompatibility. However,β-TCP has disadvantages like big brittleness, poor toughness and high elastic modulus, which limits it application in clinic. To satisfy the demand for mechanical and biological properties of bone replacement materials, composite materials betweenβ-TCP and polymer have been studied.In this dissertation, β-TCP/ Poly L-latic acid(PLLA) composite materials with good mechanical compatibility and stability has been prepared. Adjustable biodegradation, suitable mechanical properties, controllable surface microenvironment and feasible processability of the materials are emphasized.1. CaCO3 powers were prepared to β-TCP powers. First, High-purity and ultrafine CaCO3 powers were mixed to slurry with water. Then, CaCO3 slurry was poured rapidly into phosphoric acid solution according to Ca/P=1.50 in ultrasonic agitation to obtain ultrafine and uniform TCP precursor powders (0.5~2m). Finally,ultrafineβ-TCP powers were prepared by calcining TCP precursor at 950℃. Palmitic acid modifiedβ-TCP powders were obtained by adding ultrafine β-TCP powers into 1wt% palmitic acid / alcohol solution, and following ultrasonic agitation for 20min , pumping, filtrating and drying. The modification parameter was determined, and the modification effect had been tested. Scanning electron microscope (SEM) observations indicate that: 1). Surface modified β-TCP microparticles disperse uniformly; 2).The diameter of the particles is about 0.2~1.0m; 3). The particles could be uniformly distributed within PLLA matrix. The contact angle of modifiedβ-TCP powder for distilled water reaches 145.5°. The mechanical properties of β-TCP/PLLA could be enhanced by modifyingβ-TCP surface with palmitic acid. XPS test prove that a -OH group has been formed between H+ of palmitic acid and [O] of PO43- inβ-TCP. This –OH group could form hydrogen bond with –C=O of PLLA, by which the mechanical properties of the composite could be reinforced.2. The composites were prepared by mixing the modified β-TCP and PLLA according to the weight ratio of β-TCP /PLLA=2:1, 1:1, and 1:2 in this study. A process which consist of solvent casting, compression molding and leaching stage had been used to fabricate macro-porous composite materials ofβ-TCP/PLLA composite. The porosity of the composites ranges from 39~75% when the porogen-NaCl added is 40, 50, 60, 70, 80% respectively. According to the melting point and the crystallinity of the composites measured by DSC, the influence of molding temperature, molding pressure and pressure time on mechanical properties, degradation of the composites and cell culture effects in vitro were studied. The effects of the porogen NaCl, of the pressure and temperature of molding on the porosity, the volume density and the mechanical characterization of composite had been investigated. The relationship between soaking time of composite and porogen-NaCl relative leaching concentration had been studied. SEM observation indicate that the scaffolds prepared have an open, uniform and interconnected porous structure with a pore size of 100–400m. Compressive strength of ~8MPa equivalent to that of cancellous bone is achieved. The porosity of scaffolds has reached ~ 60%. The porousβ-TCP/ PLLA composite materials molding in 6MPa, 120℃and adding 60wt% porogen-NaCl possess a good mechanical properties. 3. The degradation of β-TCP/ PLLA composites in vitro was studied. The composite samples were immersed in stimulated body fluid (SBF...
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