Direct ink writing of tantalum: tailorable hierarchical porous scaffold for osteogenesis

To mitigate the risk of osseointegration failure in bone defect reconstruction, innovative fabrication strategies for developing implants with optimal biocompatibility and enhanced osteogenic capacity are crucial. Hierarchical porous structures formed by the synergistic combination of macropores (∼300-600 μm) and micropores (smaller than 20 μm) can better mimic the structural characteristics of native bone, thereby promoting osteogenesis. In this study, we developed direct ink writing (DIW) technology to fabricate a graded porous tantalum scaffold designed to promote osteogenesis. In the DIW printing process, a rheologically optimized ink and carefully calibrated printing parameters were utilized, enabling stable fabrication of patient-specific scaffold precursors with well-defined macropores. Following a controlled sintering process, the scaffolds exhibited macropores (∼400-500 μm in diameter) and interconnected micropores (∼0.5-23 μm in diameter), allowing tailoring of the mechanical properties and porosity to closely approximate those of native human bone. The well-controlled hierarchical porous structure exhibited excellent biocompatibility and significantly increased osteoinductive performance both in vitro and in vivo, accelerating new bone formation. We validated the reliable customization capabilities of this DIW-based tantalum scaffold printing method. The controllable porous structure further enhances the osseointegration potential of the implant, opening promising new avenues for the development of personalized bone implants.