Magnesium phosphate functionalized graphene oxide and PLGA composite matrices with enhanced mechanical and osteogenic properties for bone regeneration

Bone defects affect millions of people annually, making bone tissue of particular interest for developing treatments. Current strategies for healing suffer drawbacks. Regenerative engineering seeks to achieve efficient bone regeneration by utilizing synthetic bone grafts to evade these drawbacks. One material that offers such benefits is a class of functional graphenic material, known as Phosphate Graphenes. While many of our studies have focused on Calcium Phosphate Graphene, magnesium is also osteogenic. Therefore, in this study, we utilized regenerative engineering techniques to incorporate Magnesium Phosphate Graphene (MgPG) into poly(lactic-co-glycolic acid) (PLGA) to fabricate composite microsphere-based matrices as a potential synthetic bone graft. Employing different amounts of MgPG within PLGA matrices, we studied the effect of MgPG on the morphological, structural, physical and biological characteristics. MgPG-containing matrices demonstrated great mechanical strength, hydrophilicity and degradability without compromising matrix morphology. Because MgPG is a graphene oxide derivative with magnesium and phosphate ions capable of supporting bone healing as inducerons, we next evaluated the cytocompatibility and osteogenic potential of these PLGA/MgPG composite matrices. MgPG matrices demonstrated high cell viability and proliferation of MC3T3-E1 cells as well as increased osteogenic activity reported by alkaline phosphatase activity, calcium deposition and gene expression of Col1a1, osteocalcin, bone sialoprotein and Sp7. Lastly, we investigated the gene expression profile of markers/targets of the canonical β-catenin dependent Wnt signaling pathway with and without inhibitor DKK1 to understand the potential underlying mechanism behind the enhanced osteogenic potential of MgPG. In response to MgPG, gene expression of β-catenin increased, while protein expression of BMP-2 and WISP-1 also increased. These results suggest the influence of MgPG on the Wnt pathway in relation to osteogenic differentiation. With further study, MgPG matrices may provide practical solutions to the problem of effectively regenerating critical-sized bone defects, which remains a challenge in orthopaedics.