Hydroxyapatite/Carbon nanotubes composite bone implants - Biocompatibility Vs Toxicity Analysis

Poor wear resistance and low fracture toughness are the main disadvantages of using hydroxyapatite (HA) for orthopaedic implants. This can be overcome by the use of Carbon nanotubes (CNTs) as reinforcements due to their versatile properties e.g. high stiffness and mechanical strength.The main aim of this study is to develop HA composite reinforced with CNTs and to investigate their biocompatibility.Methods: HA in the presence of CNTs was synthesised following a sol-gel technique. Six different types of powders were produced by altering two variables – functionalization and presence of surfactants. The composites were produced by mixing Hydroxyapatite /carbon nanotube powder with Polyvinyl alcohol (PVA) in equal proportions. Primary Human Osteoblast cells were used for the biocompatibility study. LDH, ALP, pH and Ion content analyses were performed on external media every 24 h for 3 days and at the end of the study LDH, ALP and protein assays were performed using cell homogenate to measure various cell activities. SEM analysis was also performed.Results: A drop in pH was observed after 24 h which recovered to neutral pH by the end of day 3. Total protein content was confirmed on all materials. Cell survival was analysed by performing LDH assay on cell homogenate at the end of day 3. ALP assay was performed to determine the mineralization activity of the cells. Finally, the material was qualitatively analysed under SEM and the presence of cell material was observed.Conclusions: CNTs possess properties that are highly desirable in the development of biomaterials. However, there has been controversy regarding their biocompatibility and cytotoxicity. This study explores the biocompatibility of HA /CNTs composite as bone implants. The results show that CNTs are biocompatible and can be employed in the development of bone implants