Hydroxyapatite/graphene-nanosheet composite coatings deposited by vacuum cold spraying for biomedical applications: Inherited nanostructures and enhanced properties

Recent exciting findings of the biological interactions of graphene materials have shed light on potential biomedical applications of graphene-containing composites. Fabrication of bulk composites in particular nanostructured coatings from nanosize particles/sheets yet remains elusive. Here we report hydroxyapatite (HA) and HA-graphene nanosheet (GN) composites synthesized by liquid precipitation approach and following coating deposition by vacuum cold spraying. The HA-GN composite coatings retained intact nano-structural features of both HA and GN. The impact of the HA-GN particles during coating formation created layered coating structures and mechanical interlocking was achieved by even distribution of GN. In vitro cell culture assessment showed that filopodia of osteoblast cells inclined to move towards and got anchored by GN. Further observation by electron microscopy of adsorption of fibronectin on GN by negative staining showed fast adsorption of fibronectin in unfolded shape with the length of ∼100-135 nm. This presumably accounts for the enhanced spreading and subsequent proliferation of the cells on the GN-containing coatings. The strategy of depositing the novel HA-GN composite coatings gives bright insight into potential biomedical applications of the composites.