Graphene oxide and in-situ 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 in-situ 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 in-situ 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 in-situ 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 in-situ carbon and GO synergistically promoted more effective bone mineralization, demonstrating enhanced osteoinductivity in vitro. In a rodent model, the bioceramic scaffolds also exhibited improved osteogenesis in critical bone defects. Therefore, in-situ 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.