Fabrication and properties of carbon nanotube-reinforced hydroxyapatite composites by a double in situ synthesis process

Carbon nanotube (CNT)-reinforced hydroxyapatite (HA) composites were successfully fabricated by a double in situ synthesis process, which combined the in situ synthesis of CNTs in HA powders by chemical vapor deposition (CVD) with the further encapsulation of CNTs using HA by a sol–gel method. This double in situ synthesis approach not only improves the homogeneous dispersion of CNTs within the HA matrix, but also enhances the interfacial bonding between the CNTs and HA, thus leading to enhanced mechanical properties. Flexural tests indicated that the flexural strength of the composite is 1.6 times higher than that of pure HA, and significantly higher than that of the commercial and in situ synthesized CNT/HA composites. Furthermore, the in vitro cell culture experiments indicated that the CNT/HA composites fabricated by this double in situ process significantly accelerate the proliferation of fibroblast cells (L-929), compared with those fabricated by traditional methods, confirming their biocompatibility. With this biocompatibility and excellent mechanical properties, the obtained CNT/HA composites have a high potential as biomaterials, particularly in bone tissue engineering applications.