Recently, Professor Hua Li’s group at theNingbo Institute of Materials Technology and Engineering (NIMTE), the Chinese Academy of Sciences developed a novel HA/graphene-nanosheet (GN) composite coating deposited by vacuum cold spray (VCS) for biomedical applications. Bioceramics like HA-based composites are usually used as biocompatible coatings on metallic alloy implants. The researchers managed to synthesize HA-GN nanocomposites by a wet-chemical approach followed by VCS coating deposition. The coatings are uniform in tailorable thicknesses, and showed enhanced adhesive strength and fracture toughness.
The synthesized HA-GN nanocomposites (left image) and topographical and cross-sectional views of the as-deposited nanocomposite coatings.
Comprehensive microstructural characterization showed that the physical characteristics of the starting feedstock were completely inherited by the as-deposited coatings without detectable crystal grain growth or phase changes. In vitro cell culture assessment showed that filopodia of osteoblast cells inclined to move towards and eventually got anchored by GN. Further observation by electron microscopy of adsorption of typical key serum protein fibronectin on GN by negative staining showed fast adsorption of fibronectin in unfolded shape with the length of ~100-135 nm. It is established that upon contact of cells with biomaterials, selective and competitive absorption of key serum proteins on biomaterial surface is the initial event participating in cell-biomaterial interactions. The early adsorption and stretching state of fibronectin presumably suggests that GN promotes its adsorption, which in turn facilitates attachment and spreading of the cells.
The findings shed light on potential biomedical applications of the novel graphene-containing nanocomposites for repair/replacement of hard tissues. Part of the ongoing research efforts of Hua Li’s group are devoted to investigating how the surface chemistry and morphology of the GN-containing coatings affect competitive adsorption and conformational changes of absorbed multiple serum proteins and how the absorbed proteins on their surfaces mediate the cellular behaviors. Through the researchers’ study in molecular level of how the absorbed proteins function, they expect to create a deeper understanding of cell-biomaterial interactions and hence improve our ability to predict and control the biocompatibility of new biomaterials.
