Abstract
Recently, graphene-based nanomaterials, in the form of two dimensional substrates or three dimensional foams, have attracted considerable attention as bioactive scaffolds to promote the differentiation of various stem cells towards specific lineages. On the other hand, the potential advantages of using graphene-based hybrid composites directly as factors inducing cellular differentiation as well as tissue regeneration are unclear. This study examined whether nanocomposites of reduced graphene oxide (rGO) and hydroxyapatite (HAp) (rGO/HAp NCs) could enhance the osteogenesis of MC3T3-E1 preosteoblasts and promote new bone formation. When combined with HAp, rGO synergistically promoted the spontaneous osteodifferentiation of MC3T3-E1 cells without hindering their proliferation. This enhanced osteogenesis was corroborated from determination of alkaline phosphatase activity as early stage markers of osteodifferentiation and mineralization of calcium and phosphate as late stage markers. Immunoblot analysis showed that rGO/HAp NCs increase the expression levels of osteopontin and osteocalcin significantly. Furthermore, rGO/HAp grafts were found to significantly enhance new bone formation in full-thickness calvarial defects without inflammatory responses. These results suggest that rGO/HAp NCs can be exploited to craft a range of strategies for the development of novel dental and orthopedic bone grafts to accelerate bone regeneration because these graphene-based composite materials have potentials to stimulate osteogenesis.
Highlights
Calcium phosphates, such as hydroxyapatite (HAp) and β -tricalcium phosphate (β -TCP), which are known for their excellent biocompatibility and osteoconductivity, are used widely as clinically available bone substitutes[1,2,3]
It is considered that reduced graphene oxide (rGO)/HAp NCs are formed through electrostatic interactions between HAp MPs and rGO NSs
The osteogenic responses mediated by rGO/Hap NCs were more stimulated when the cells were incubated in the presence of osteogenic agents
Summary
Calcium phosphates, such as hydroxyapatite (HAp) and β -tricalcium phosphate (β -TCP), which are known for their excellent biocompatibility and osteoconductivity, are used widely as clinically available bone substitutes[1,2,3]. Owing to the very low absorption rate of HAp and its trabecular structure that helps introduce blood cells and bone cells, new bone deposition can be accelerated This means that the material has the features of a scaffold with excellent biocompatibility[5,6]. On the other hand, according to a series of experimental studies, the proliferation and differentiation of osteoblasts was very low in the presence of HAp compared to the other bone substitutes[7] To overcome this limitation, trials have been conducted to combine the osteoconductive scaffold with an osteoinductive protein to enhance the bone regeneration performance. Fewer studies have evaluated the use of graphene to prepare scaffolds for tissue engineering These have typically involved assessing the cell response in vitro and have reported improved cell response. This study explored the potential of rGO/HAp nanocomposites (rGO/HAp NCs) to enhance osteogenesis both in vitro and in vivo
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