Paper Title
A Multifunctional Carbon Nanofiber/Bioceramic Coating For Orthopedic Applications

Abstract
Carbon nanofibers (CNF), one of the most significant nanomaterials with unique mechanical, biological and surface properties, has been shown as suitable for various biomedical applications. In the present work we report the development of CNF reinforced mineral (manganese) substituted hydroxyapatite (Mn-HAP) composite on titanium alloy (Ti6Al4V). Hydroxyapatite (HAP, [Ca10(PO4)6(OH)2]) is a widely used biomaterial for bone implant applications due to its osteoconductive and bioactive properties. Application of HAP in orthopedic implants suffers from its low fracture toughness and poor wear resistance. To surmount these issues, CNF is used as an excellent reinforcement material for imparting strength and toughness to brittle HAP. The phase composition and surface microstructure of the obtained coating were evaluated by FT-IR, XRD and SEM-EDX, respectively. The effect of reinforcement of CNF and the substitution of Mn in HAP on the mechanical and biological properties of the CNF/M-HAP coating was investigated. Also, the corrosion resistance of the composite coating on Ti6Al4V substrate in SBF was evaluated by potentiodynamic polarization studies. The cytotoxicity of the CNF/M-HAP composite coated Ti6Al4V was analyzed towards human osteoblast (HOS MG63) cells using MTT assay. The in-depth analysis of the results obtained in this study facilitates a better understanding of the CNF/Mn-HAP composite coating. The reinforcement of CNF in Mn-HAP could significantly enhance the adhesive strength of the coating. In addition, the substitution of Mn in HAP improves the biocompatibility of the coating which can be well evident from the cell culture results. Thus, the combination of mechanical property of CNF and the biocompatibility of Mn-HAP makes the CNF/M-HAP composite coating an ideal choice for orthopedic implant applications. Index Terms� Carbon nanofiber, Manganese substituted hydroxyapatite, Orthopedic applications, Ti-6Al-4V