Graphene oxide coating on two-dimensional glass substrates and three-dimensional zirconia scaffolds for bone tissue regeneration

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Zirconia (ZrO 2 ) scaffolds are considered promising candidates for bone regeneration owing to their excellent biocompatibility and mechanical strength. However, intrinsic bioinertness and the formation of microcracks during sintering remain major challenges that limit their clinical translation. Graphene oxide (GO), characterized by its abundant functional groups and outstanding mechanical properties, has emerged as a valuable material in tissue engineering applications. To address these issues, a silane-mediated dip-coating strategy was employed to deposit GO onto both two-dimensional glass substrates and three-dimensional (3D) ZrO 2 scaffolds, resulting in the design and fabrication of a novel 3D porous GO-ZrO 2 composite scaffold. The GO-coated glass substrates and GO-ZrO 2 scaffolds were comprehensively characterized using multiple analytical techniques. The biocompatible and osteogenic abilities of human dental pulp stem cells (hDPSCs) seeded onto the scaffolds were assessed in vitro . Furthermore, the bone regeneration performance of the GO-ZrO 2 scaffolds were evaluated in a rat calvarial critical-sized defect model. The results demonstrated that the GO layer was uniformly coated on the ZrO 2 scaffolds through covalent bonding (C-O-Si and Si-O-Zr) which effectively bridged microcracks and inhibited their further propagation. Compared with the uncoated ZrO 2 scaffolds, the GO-ZrO 2 scaffolds exhibited increased compressive strength (1.27 ± 0.09 MPa) and elastic modulus (10.71 ± 1.20 MPa). The degradation rate of the GO-ZrO 2 samples was minimal, with only a 0.54% loss of their initial weight after 3 weeks, and no signs of pH reduction or obvious structural changes. Notably, the incorporation of GO, with its abundant oxygen-containing functional groups, significantly promoted cell adhesion, proliferation, and osteogenic differentiation of hDPSCs in vitro . Mineral deposition was markedly improved, as reflected in an increased calcium-to-phosphorus (Ca/P) atomic ratio (1.21 ± 0.03). Additionally, after an 8-week healing period in vivo , the GO-ZrO 2 scaffolds demonstrated robust new bone formation. Collectively, these findings indicate that the GO-ZrO 2 composite scaffolds represent a highly promising strategy for promoting bone regeneration. Scheme. Illustration of the design and fabrication of 3D porous GO-ZrO 2 scaffolds for repairing caritical-sized cranial bone defects in rats. Graphene oxide (GO) was coated onto 2D glass substrates and 3D ZrO 2 scaffolds by covalent bonds, respectively. The GO-ZrO 2 scaffolds prepared demonstrated good bioactivity, structure integrity, and mechanical properties, promoting new bone formation and effectively repairing bone defects. • Graphene oxide (GO) coating adheres strongly to 3D porous nano-zirconia (ZrO 2 ) scaffolds through covalent bonds, achieving uniform coverage with fewer layers. • GO coating improves the structural integrity, mechanical properties of ZrO 2 scaffolds. • GO coating significantly enhances the bioactivity of both 2D glass substrates and 3D ZrO 2 scaffolds. Importantly, GO-ZrO 2 scaffolds promote stem cell proliferation and osteogenic differentiation both in vitro and in vivo. • The silane-mediated dip-coating method ensures that the suspension material is uniformly coated onto 3D high-hardness material scaffolds without altering their original structure.

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