| In the Face of the phenomenon of increasing bone defects in the clinic, biomedical composite research is becoming more and more important for bone repair. With the development of nanotechnology, it is suggested that nanomaterials have been used to improve the overall performance of bone repair materials for meeting the need of orthopedic clinical applications. Great attention has been paid to the carbon nano tubes (CNTs)/hydroxyapatite (HA) composites for bone repair application. Owing to the special nanostructure and excellent mechanical property of CNTs with magnetic property, it is hoped that the mechanical properties of HA can be effectively improved by CNTs addition. It is also hoped that the CNTs/HA composites will have a certain magnetic property, which favor its application in bone repair and replacement. However, CNTs/HA composites fabricated by the existing methods reported in the literature fail to exhibit the expected macroscopic properties such as stiffness and strength. The reasons of CNTs nanoparticles agglomerating, unevenly distributing in HA matrix, and its intact structure damaging in the process of CNTs/HA fabrication, have become the obstacles to improve the mechanical properties of the CNTs/HA composites. In order to fabricate the CNTs/HA composites with excellent mechanical properties, in this dissertation, the methods of phycial blending (PB), chemical coprecipitation (CC), biomimetic mineralization (BM) and in-situ growth (IS), have been used to fabricate the CNTs/HA composites. Moreover, the CNTs/HA composites prepared by the above-mentioned methods have been used as one of calcium phosphate cement (CPC) solid phase for the CPC preparation. The main contents are as follows.In the process of fabricating CNTs/HA composites by PB method, silane coupling agent KH-792 was used as a surfactant, and it can interact simultaneously with CNTs and HA in the form of chemical bonds. When the addition amount of KH-792 was 6wt%, CNTs can be evenly dispersed in HA matrix in the composites. At the same additive amount of KH-792, the CNTs/HA composites (CNTs mass percentage content of 5%) have the best performance in compressive strength and Young’s modulus.In the process of fabricating CNTs/HA composites by CC method, the length of CNTs has been shortened and the tube walls of CNTs have a certain degree of damage in these obtained composites. Moreover, in these CNTs/HA composites, there is the CNTs agglomeration distributing in the HA matrix, and the acting force came from the interface between the CNTs and the HA is weak. The crystal size of HA on the main lattice plane is within 20 nm in these obtained composites. In addition, a small amount of bioglass was added in the HA matrix during the fabrication of the CNTs/HA composites. The phase compostion of these as-obtained compositions has not been affected, and the performances in compressive strength and Young’s modulues of these composites have got a certain degree of increase after the bioglass addition.When the CNTs/HA composites were fabricated by BM method,2 times simulated body fluid (SBF) was used as the immersion medium for CNTs. After immersion in 2×SBF for 7 days, nanosized bone-like apatite crystalline has been formed on the CNTs surface. In the as-obtained CNTs/HA composites, the tube walls and the tube length of CNTs have been damaged for a certain degree. The bone-like apatite crystalline shows the preferential growth on (002) crystal plane. Moreover, the lattice boundary between CNTs and HA is obvious and the acting force between CNTs and HA is weak in these composites.Using IS method for the preparation of CNTs/HA composites, HA by adding a certain amount of FeCl3 MgCl2 mixture was used as the matrix in the chemical vapor deposit ion (CVD) system. It has been proven that the CNTs/HA composites can be successfully fabricated by IS method combining the CVD system, while FeCl3 @ MgCl2 mixture with mass ratio of 2/8 was added into HA slurry. Under this fabricating condition, more than 20 wt% multi-walled CNTs with a average diameter of 40-65 nm can in-situ grow form HA crystalline in these composites. Moreover, it was observed that the tube walls of CNTs with high degree of graphitization are smooth and the nanotube structure is intact in these composites.Meanwhile, when pure HA without any salt added was used as the matrix for CNTs production, the CNTs/HA composites can be successfully preparedby the IS method in CVD system. In the process of the preparation of CNTs/HA composites, when pure HA matrix was sintered at the temperature of 1200℃ for 2h, a small number of multi-walled CNTs (with mass percentage of 1%) have grown in-situ from the HA matrix. The average diameter of the CNTs in these composites is in the range of 50-80nm.The CNTs/HA composite disks or porous cylinders have been prepared by using the CNTs/HA composite powder obtained by the aforementioned four methods. It was found that under the condition of the compressive stress load, the CNTs/HA porous cylinders prepared using the composite powder by IS method show the best performance in the mechanical properties. In addition, the four CNTs/HA composites all show a certain paramagnetic behavior and the saturation magnetization of the composites prepared by IS method is the maxmium and that of the composites prepared by PB method is the minimum in the four composits.The CNTs/HA compsite powder obtained by the aforemention four methods were used as one of the solid phase for CPC preparation. It has proven that that CPC reinforced with CNTs can be successfully prepared by using PBS buffer as the liquid and the solid liquid ration of 0.47 mL·g-1 for CPC preparation. When the four CNTs/HA composite powder was employed for CPC preparation, it is found that the phase composition of CPC has not been affected and the initial setting time and final setting time of CPC have been shorten, but all accord with the clinic requirement of CPC. Compared with the pure CPC, four CPC samples reinforced with CNTs have a decrease in contact angle and an increase in surface energy. There is no significant difference in the contact angle and surface energe in the four CPC samples. Moreover, in the process of the minerization in vitro, nanoscale bone-like apatite layer with different thicknesses can be formed on the surface of the four CPC samples. CPC-PB and CPC-CC samples have the best ability in inducing the formation of bone-like apatite in vitro, and CPC-IS sample has the worst ablility of inducing the formation of bone-like apatite in vitro. Under the condition of the compression stress loading on the four CPC samples, CPC-PB sample has the best compressive mechanical properties, and comared with the control samples, the elastic modulus and compressive strength of the CPC-PB samples have been increased by 96%and 95%, reapectively.Cell culture in vitro results showed that in the absence of static magnetic field (SMF), the osteoblast proliferation on the four kinds of CPC samples is lower than the control samples, and there is no significant difference in the osteblast proliferation ability on the four kinds of CPC samples in the cell cuture for 7 days. It showed that ALP activity of the CPC-PB and CPC-IS samples is much higher that of the control samples. However, in the present of SMF, osteoblast proliferation ability in four kinds of CPC samples has become very different. With CPC sample culturing with osteoblast for 7 days, the proliferation ability of osteoblast on CPC-IS samples is much higher than the control samples. In addition, ALP activity values of the four kinds of CNT/CPC samples are higher than that of the control samples. In particular, CPC-IS samples have the highest ALP activity in the four samples. It indicated that under the stimulus of the SMF, the presence of magnetic CNTs promoted the differentiation of osteoblast on the CPC, and the CPC-IS samples shew the strongest role in promoting osteoblast differentiation.Cell culture in vitro results showed that compared with no SMF action, under the action of SMF, the CPC samples have a more favorable spread of the osteoblasts with more /pseudopodia. There is a better adhesion of the osteoblast on the surface of the CPC. The entire structure of the osteoblast adhering on the surface of CPC samples is richer, the three-dimensional stereo sense is stronger, and the connections between osteoblasts are more and better. The CPC-IS samples have the most outstanding behavior in the morphologies and cell structure of the osteoblasts adhering on their surface. |
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