Enhanced Osteogenesis by Reduced Graphene Oxide/Hydroxyapatite Nanocomposites

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.

Graphene and graphene oxide as nanomaterials for medicine and biology application

“…Calvarial defects of critical sizes were produced in rabbits and then cured with GO/β-TCP scaffold, which resulted in higher rate of naive bone formation than defects filled by unchanged β-TCP alone [126]. Similar observations were also found in the case of rGO/HAp graft which showed considerably higher (52%) bone density than HAp (26%) as well as untreated control (17%) [127].…”

Graphene-based materials for tissue engineering

“…Graphene-based materials have been combined with HAP to enhance osteogenic differentiation of cells and formation of new bone [146, 149, 150]. It was reported that GO/CaCO 3 or graphene/CaCO 3 hybrid composites can enhance formation of HAP when incubated in simulated body fluid (SBF) solution [146].…”

“…rGO sheets and HAP microparticles can adhere with each other through electrostatic interactions and hydrogen-bonding [149, 150]. The positively charged calcium moieties on the surface of HAP microparticles can be immobilized on the negatively charged hydroxyl and carboxyl groups on the surface of rGO sheets via electrostatic interactions.…”

Dicalcium Phosphate Coated with Graphene Synergistically Increases Osteogenic Differentiation In Vitro

“…Therefore, the DCP-rGO composites could be successfully formed because of the unique structural properties of rGO sheets. In addition, the interfacial and hydrogen bond interactions between the oxygen-containing surface groups of rGO and the hydroxyl groups of DCP microparticles could also participate in the good adhesion between DCP microparticles and rGO [50,57,58]. Figure 3b showed the Raman spectra of DCP microparticles and DCP-rGO composites.…”

“…The rGO sheets were obtained by the preparation of GO using the modified Hummers and offeman method, and subsequent reduction process of GO with hydrazine hydrate (N 2 H 4 ·H 2 O) at 100 • C for 24 h [38,49,50]. The prepared rGO sheets in deionized water were sonicated for 2 h. The DCP microparticles dispersed in deionized water were physically mixed at DCP to rGO weight ratios of 2:1, 1:1, or 1:2, respectively.…”