The Physical And Mechanical Properties Of Fibroin/Hydroxyapatite Scaffold

Finding the bone defect materials become the hot spot in the biomaterials field.Hydroxyapatite with the similar compositions of the bone can be rapid fixed, bond between the osteogenesis and scaffold, and replaced by the new osteoblast. These virtues have been verified in many mammal experiments and clinic, but it too brittle, and easily crush in bone. Silk from the silkworm contains eighteen different kinds of amino acid and some different structure, and used as the biomedical suture for centuries. Its unique properties, such as biocompability, non-immunogenic response, controllable degradation in vino and robust mechanical properties provide its application in the medical materials. Therefore, the mechanics will be increased by combining both HA and fibroin, which might be used in the field of human bone.In this study, the fibroin/hydroxyapatite scaffold is successfully prepared by dissolving both fibroin and hydroxyapatite in the phosphate buffer, cross-linked by glutaral dehyde in moderate condition, which possesses both crystalline structure andβparallel. HA/SF composites were investigated with Fourier transform infrared spectroscopy(FTIR), X-ray diffraction(XRD),transmission electron microscopy(TEM). Mechanical properties of the scaffold were performed on AGS-J universal test machine. The result shows that the maximum elastic modulus and compressive strength of this scaffold can attain about 48.087MPa and 1.44MPa, respectively, when the ration of fibroin/hydroxyapatite is 6/4. The porosity is 70%. The pore size ranges from 50μm to 200μm. All the results suggest this new method can highly promote the scaffold's mechanical properties which significant approach the cancellous bone of human.In order to find the optimal way to promote the scaffold's mechanical properties, we try to change the temperature, time of the freezing dry, the proportion of NaHCO₃, glutaral dehyde, the time of the solidification,pH and concentration and et al. in the further field and analyze all of the above factors at the end. The result verified both concentration and the temperature are very important. The optimal mixture ratio of the solid and liquid is 1:1. The elastic modulus will reach about 74.98MPa which is much better than the theorestic request of cancellous bone of human. The reaction condition 40℃,100% is better than the other way, which promote the utilization. In the aspect of mechanics, compression modulus increased with the increase of the glutaral dehyde ratios in the scaffolds, but it will cost by toxicity. So in practice we need to decrease the content of it. the elastic mode will be enhanced by adding 2% Methanol. And the scaffolds porosity will decrease the mechanical of the scaffold, so we can change the mechanical properties by the different addition. In order to extend the conservation time, it can be decreased the humidity, and 8h is the best period for the freezing dry.