Graphene oxide and <i>in-situ</i> carbon reinforced hydroxyapatite scaffolds via ultraviolet-curing 3D printing technology with high osteoinductivity for bone regeneration

Ultraviolet photopolymerization additive manufacturing has been used to fabricate calcium phosphate (Ca-P) ceramic scaffolds for repairing bone defects, but it is still a challenge for 3D printed Ca-P scaffolds to simultaneously enhance the mechanical strength and osteoinductivity. Here, we successfully developed a high-performance hydroxyapatite (HA) scaffold containing<i>in-situ</i>carbon and graphene oxide (GO) by precisely regulating the degreasing and sintering atmosphere. The results indicated that the mechanical properties of HA scaffolds could be significantly improved by regulating the amount of<i>in-situ</i>carbon. The HA scaffold containing 0.27 wt.% carbon achieved the maximum compressive strength of 12.5 MPa with a porosity of approximately 70%. The RNA transcriptome sequencing analysis revealed that<i>in-situ</i>carbon could promote osteogenic differentiation by improving oxygen transport and promoting the expression of multiple angiogenic factors. More importantly, in the absence of osteoinductive agents, the<i>in-situ</i>carbon and GO synergistically promoted more effective bone mineralization, demonstrating enhanced osteoinductivity<i>in vitro.</i>In a rodent model, the bioceramic scaffolds also exhibited improved osteogenesis in critical bone defects. Therefore,<i>in-situ</i>carbon and GO could simultaneously enhance the mechanical strength and osteoinductivity of HA scaffolds, effectively achieving substantial endogenous bone regeneration. This strategy will provide a simple and energy-efficient approach for engineering osteoinductive ceramic scaffolds for repairing bone defects.