Electrodeposition and biomineralization of nano-β-tricalcium phosphate on graphenated carbon nanotubes

Nano-calcium-phosphate (n-CaP) is an attractive, biocompatible material for increasing osteointegration. Among nanomaterials, functionalized carbon-based materials are emerging materials, which have excellent mechanical properties, biocompatibility and chemical stability. These properties may further enhance the n-CaP performance. It has been shown that stoichiometric n-CaP can be electrodeposited on graphene and carbon nanotubes (CNTs) by employing fast and low-cost electrodeposition techniques. Here, we present, for the first time, a crystalline, needle-like nano-β-tricalcium phosphate (n-β-TCP) electrodeposited on reduced graphene oxide (rGO) nanosheets. The rGO was grown on CNT, as a composite biomaterial, in a one-step process, followed by electrodeposition of n-CaP. The results show that, in acidic pH, needle-like crystals appear on the surface. It is speculated that the carboxyl (carboxylic acid)/carboxylate functional groups attached directly to the rGO are essential in accelerating OH^- formation and deposition of needle-like n-CaP crystals. High-resolution scanning electron microscopy, transmission electron microscopy, energy dispersive X-ray spectroscopy, and X-ray diffraction elucidated homogeneous, highly crystalline, n-CaP (β-tricalcium phosphate) crystals. This composite presented an excellent in vitro biomineralization after soaking in simulated body fluid.