BackgroundHydroxyapatite/polyamide 66 (HA/P66) has been clinically used for several years owing to its good biocompatibility and bioactivity. However, it has been found that the osseointegration process of the HA/P66 implant takes a large amount of time because of the small amount of HA on its surface.MethodsTo increase the amount of HA and aid faster osseointegration, we prepared a HA coating using a biomimetic process assisted by polydopamine (PDA) on the HA/P66 substrate. The surface properties of the substrate modified by PDA and HA were characterized, and the capacity of biomaterials for osteogenic induction was investigated both in vitro and in vivo.ResultsThe HA coating was successfully prepared on the HA/P66 substrate and verified by X-ray photoelectron spectroscopy (XPS), scanning electron microscopy (SEM), and X-ray diffraction (XRD). The HA coating remained firmly attached to the underlying PDA-HA/P66 substrate even after strong ultrasound treatment for 1 h, and the calcium and phosphorus of the HA coating was continuously released in vitro in a slow manner. The formation of the HA coating on the PDA film greatly increased the hydrophilicity and surface roughness of HA/P66. In cell-based experiments, as compared with the HA/P66 substrate, the HA coating formation on the PDA film could facilitate the functions of C3H10T1/2 cells, including cell adhesion, proliferation, spreading, alkaline phosphatase activity, calcium nodule formation, and expression of osteogenic differentiation-related proteins. In addition, the HA/P66 scaffolds modified with PDA and HA coatings were implanted in rabbit femoral condyles. At 8 weeks after surgery, micro-computed tomography scanning (micro-CT) and hematoxylin–eosin (HE) staining revealed that more new bones were formed around the HA/P66 scaffold that was modified with a PDA-assisted HA coating.ConclusionThese results indicate that the preparation of a PDA-assisted HA coating by using a biomimetic process significantly improves the capacity of biomaterials for osteogenic induction.
Bone plates have been applied to fix fractures for over a hundred years. Metal plates are the gold standard. However, an increasing number of clinical practices and animal experiments have shown that metal plates have had incidents of failure due to their rigid fixation and long-term complications. Degradable composites present the advantages of a lower elastic modulus and absorbable properties but are unsuitable for load-bearing applications. Nondegradable bone plates composed of a nanohydroxyapatite/polyamide 66/glass fiber (n-HA/PA66/GF) composite are prepared, which have enough strength and a low elastic modulus for an internal fixation device. To better assess its function as a bone plate, animal experiments are conducted using a canine load-bearing femur fracture model. The results show that the n-HA/PA66/GF plate can fix fractures effectively. Gross observation, radiographic films, and histological analysis all show that the n-HA/PA66/ GF plate leads to a secondary (indirect) union with obvious callus formation, whereas the titanium plate leads to primary (direct) union due to rigid fixation. Furthermore, the histological results reveal that new bone grows at the interface and that the n-HA/PA66/GF plate can integrate with native bone tissue. Consequently, the n-HA/PA66/GF composite shows good potential as a bone plate to fix loading-bearing bone fractures.
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