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[Nano-hydroxyapatite/collagen composite for bone repair]
Qing-ling Feng1, Fu-zhai Cui, Wei Zhang
1Department of Material Science and Engineering, Tsinghua University, Beijing 100084, China. biomater@mail.tsinghua.edu.cn
Objective:
To develop nano-hydroxyapatite/collagen (NHAC) composite and test its ability in bone repairing.
Methods:
NHAC composite was developed by biomimetic method.
Results:
The composite showed some features of natural bone in both composition and microstructure. The minerals could contribute to 50% by weight of the composites in sheet form. The inorganic phase in the composite was carbonate-substituted hydroxyapatite (HA) with low crystallinity and nanometer size. HA precipitates were uniformly distributed on the type I collagen matrix without preferential orientation. The composite exhibited an isotropic mechanical behavior. However, the resistance of the composite to localized pressure could reach the lower limit of that of femur compacta. The tissue response to the NHAC composite implanted in marrow cavity was investigated. Knoop micro-hardness test was performed to compare the mechanical behavior of the composite and bone. At the interface of the implant and marrow tissue, solution-mediated dissolution and macrophage-mediated resorption led to the degradation of the composite, followed by interfacial bone formation by osteoblasts. The process of implant degradation and bone substitution was reminiscent of bone remodeling.
Conclusion:
The composite can be incorporated into bone metabolism instead of being a permanent implant.