Enhancing the Mechanical and Biological Performance of Bone Scaffolds with Reduced Graphene Oxide

Bone grafting procedures are the second most frequent tissue transplantation, with over two million procedures taking place annually worldwide. There has been a growing demand to develop synthetic bone graft substitutes to overcome the shortage of bone tissue for transplantation. Having expanded into biomedical applications, graphene and its derivatives have attracted significant interest for use in biomaterials due to their unique and remarkable properties. In this work, we developed porous composite scaffolds by incorporating reduced graphene oxide (rGO) into poly(L-lactic-co-glycolic acid) microsphere-based scaffolds, and investigated whether the addition of small amounts of rGO can produce structures that are both mechanically competent and biologically active for bone regenerative engineering. The scaffolds with varying concentrations of rGO were successfully fabricated via the oil-in-water emulsion method. The encapsulation and presence of rGO within the polymeric microspheres was confirmed and the physicochemical and microstructural properties of the matrices were evaluated. The addition of rGO, in the moderate range, significantly improved the compressive strength and stiffness of the composite matrices; however, at higher concentrations there was excessive aggregation and re-stacking of the sheets resulting in deterioration of the mechanical properties. All rGO concentrations were well-tolerated by stem cells in vitro and none of the scaffolds elicited any cytotoxic effects. Importantly, the moderate ranges of rGO were shown to promote stem cell osteogenic differentiation, corroborating findings that graphene-based materials may exhibit osteoinstructive effects. Furthermore, an in vivo study was performed to evaluate the bone regenerative potential and biomechanical competency of these scaffolds in a in a critical-sized load-bearing bone defect model in New Zealand White rabbits.