| As for researches involving biomaterials for bone repair and/or substitute, how to design and fabricate biomaterials with excellent biomimetic properties is a crucial step to make the clinical healing and permanent augmenting of bone defects come true. The physic-chemical property and biological property are of great importance for any new biomaterial because the former can let biomaterials play full functions and the latter determine whether the material can be used clinically. The interaction between biomaterials and host tissues is a complicated process subjected for influences of various factors. So, it is essential to simplify the model of property evaluation. In vitro test is just such an optimum choice, through which we can gain knowledge of the fundamental performances and rules of changes, and thus can provide references for further investigating the behaviors of biomaterials in vivo environment as well as the interactions between biomaterials and human body.According to the principle for designing nano-composites, bioactive composite made of polymer and dispersive inorganic phase of nano-hydroxyapatite (n-HA) was prepared by biomimetic route. n-HA/Polyamide66 (n-HA/PA66) composite was fabricated with a solution co-mixing method, on which the in vitro property tests and the biocompatibility evaluation was carried out. On the basis, the bioactivity of the composite soaking in simulated environment was studied. In addition, a composite for drug delivery was investigated preliminarily.1. n-HA crystals slurry, was prepared by mixing (NH4)2HPO4 and Ca(NO3)2 solutions with a pH>10. Then PEG6000, DMAC and PA66 were added into the slurry at certain temperature. n-HA/PA66 composites with 20wt% n-HA and 40wt% n-HA were obtained respectively. A stable chemical interface bonding formed between the two phases of n-HA and PA66 which were confirmed by the measurements using TEM, FT-IR, XRD etc. Besides, the chemical component of the two phases in the composite has no change before and after compounded. It indicates that the n-HA/PA66composite will has good stability, mechanical property and favorable machinability.2. In vitro tests showed that pure PA66 has a higher water sorption rate than that of the n-HA/PA66 composite when immersing in water, which indicates that the introduction of n-HA into the PA66 matrix decreased water sorption rate of PA66. During the immersion, pure PA66 had almost no weight loss, while slight weight loss is detected for the composite. This phenomenon was severer in acid media than that in neutral media. According to the measurement of ICP, there is an increase in the concentration of Ca and P in the mediums liquid, showing that dissolution of n-HA in the composite has taken place to some extent. However, no degradable monomers from the PA66 can be detected. The morphology of both pure PA66 and the composite have no obvious change before and after immersion in 0.9% NaCl solution and in citric acid solution. Moreover, there is no structural change resulted from degradation and/or decay in the composite. The composite possesses good chemical stability. The deposition of Ca/P particulates on the surface demonstrates that n-HA/PA66 composite is highly bioactive.3. The results of immersion in SBF showed that the dissolution-deposition mechanism was prominent in the surface of the composite when immersed into solutions containing Ca and P. The deposition of Ca and P as well as the change of Ca/P ratio are similar to the process of new bone formation. In XRD test, with the time increase of n-HA/PA66 composite immersed in SBF, the characteristic peak of n-HA at 2 =31-35 became stronger, meanwhile, two new peaks at 2 =16 and 30?appeared, which were ascribed to the specific peaks of TCP phase. From theanalysis of XRD and IR, it could be seen that those deposited particulates on n-HA/PA66 surface belong to poorly crystalline carbonated HA crystals, closely similar to the natural bone apatite, which play an important role in bone regeneration. However, for the PA66 controls, there is no Ca-P deposit... |
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