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Background: As the major inorganic component of natural bone, nano-hydroxyapatite (n-HA) on its own is limited in its use in bone repair, due to its brittleness. Chitosan (CS) and sodium alginate (SAL) are used to reduce its brittleness and tendency to degradation. However, the compressive strength of the composite is still low, and its biological performance needs further study., Methods: Nano-hydroxyapatite/sodium alginate/chitosan (n-HA/SAL/CS) composite was prepared via an in situ synthesis method. Further, we prepared the n-HA/SAL/CS self-setting bone repair material by mixing n-HA/SAL/CS powder with a curing liquid (20 wt.% citric acid). In addition, the in vitro bioactivity and cell cytotoxicity were also explored., Results: Transmission electron microscopy photos revealed that the n-HA crystals were uniformly distributed throughout the polymer matrix. Infrared IR spectroscopy indicated that the HA interacted with the COO - of SAL and NH 2 - of CS. The compressive strength of the n-HA/SAL/CS bone cement was 34.3 MPa and matched the demands of weight-bearing bones. Soaking in vitro in simulated body fluid demonstrated that the composite material had reasonably good bioactivity, while cytotoxicity tests indicated that the n-HA/SAL/CS cement could promote cell proliferation and was biocompatible., Conclusions: Compressive strength of n-HA/SAL/CS can satisfy the needs of cancellous bone, and in vitro bioactivity and cytotoxicity tests results indicated that the n-HA/SAL/CS composite could act as an optimal bone repair material.

In this work, we investigate the enhanced mechanical properties of nano-hydroxyapatite/polyamide 66 (nHA/PA66) composites reinforced with multi-walled carbon nanotubes (MWCNTs) by means of the blending method. The MWCNTs-nHA/PA66 composites were characterized by various techniques, and the obtained results indicated that the MWCNTs were evenly distributed in the composite and that good interfacial bonding was formed between MWCNTs and PA66. The addition of MWCNTs improved the crystallinity of PA66, while it had little or no effect either on the composition or on the crystal structure of the composites. Moreover, the addition of MWCNTs in nHA/PA66 significantly improved the mechanical strength, and the tensile and compressive strengths attained maximum values of 90.3 and 126.8 MPa, respectively, with the addition of 0.1 wt% MWCNTs, whereas the bending strength attained a maximum value of 105.5 MPa with the addition of 0.05 wt% MWCNTs. Finally, L929 cells co-cultured with the MWCNTs-nHA/PA66 composite exhibited comparatively uninhibited cell growth, indicating that the addition of MWCNTs had negligible effect on the cytocompatibility of the original nHA/PA66 composite.

The combination of nano-hydroxyapatite (n-HA) and polypropylene carbonate (PPC) was used to make a composite materials by a coprecipitation method. The physical and chemical properties of the composite were tested. Scanning electron microscope (SEM) observation indicated that the biomimetic n-HA crystals were uniformly distributed in the polymer matrix. As the n-HA content increased in the composite, the fracture mechanism of the composites changes from gliding fracture to gliding and brittle fracture. Furthermore, the chemical interaction between inorganic n-HA and polypropylene carbonate was also investigated and discussed in detail. The hydrogen bonds might be formed between -OH/CO3(2-) of n-HA crystal and the ester group (-COO-) of PPC. The tensile strength of n-HA/PPC (40/60) was similar to that of the cancellous bone, and reached ca 58 MPa. The osteoblasts were cultured for up to 7 days, and then the adhesion and proliferation of osteoblasts were measured by Methyl thiazolyl tetrazolium (MTT) colorimetry assay and SEM. The cells proliferated, grew normally in fusiform shape and well attached. The in vitro test confirmed that the n-HA/PPC composites were biocompatible and showed undetectable negative effect on osteoblasts. In vivo implantation of the composite in New Zealand white rabbits was performed. It can stimulate the growth of a new bone, and at the same time the material begins to degrade. These results suggested that the composite may be suitable for the reparation or replacement of bone defects and possessed the potential for clinical applications., (Copyright © 2016 Elsevier B.V. All rights reserved.)