Overview of Hydroxyapatite–Graphene Nanoplatelets Composite as Bone Graft Substitute: Mechanical Behavior andIn-vitroBiofunctionality

Hydroxyapatite (HA) and related materials have been frequently studied as ceramic-based bone graft materials due to their outstanding biocompatibility and osteoconduction. Since the bones are the load supporting parts of a vertebrate, they must have good fracture toughness (KIC) to avoid fracture at high loading during limb movements. However, the main shortcomings of HA are the poor fracture toughness and brittleness. The mechanical properties of HA need to be improved for orthopedic applications, therefore it is often fabricated with other materials into a composite. This article focuses on the effect of carbon nanostructures (CNSs) especially graphene nanoplatelets (GNPs) on the mechanical, physicochemical properties and in-vitro bio-functional performances of HA. We provide an overview on the preparation and characterization of the HA–GNPs composites. To conclude, the challenges in the fabrication of multi-substituted HA–GNPs composites and future outlooks in the biomedical domain are discussed.