High crystallinity CSP bioceramics with excellent mechanicals for 3D printed bone regeneration repairing

Large bone defects caused by disease, physiological deformation, and accidental injury present significant challenges for clinical bone tissue repair. Calcium silicon phosphate (CSP)-based bioceramics are widely used for clinical bone defect repair with the advantages of biocompatibility and osteogenic properties. However, poor mechanical strength limits their load-bearing applications. In this work, a novel CSP-based bioceramic, Nagelschmidtite (Nagel, Ca₇Si₂P₂O₁₆), was fabricated by the molten salt synthesis (MSS), sol‒gel, and solid-state reaction methods. Materials characterization revealed the Nagel powders fabricated from the MSS method possess high crystallinity, uniform particle size distribution, and smooth particle surfaces, and their disks exhibited low porosity and high density. Benefiting from the above characterizations, the mechanical strength of the MSS sample was enhanced by roughly 6.07 times relative to the sol‒gel sample. Meanwhile, the stable degradation performance and bone mineralization ability mean that MSS samples have the potential for direct application with load-bearing sites. Furthermore, MSS Nagel can be used to support three dimensional (3D)-printed scaffolds of various shapes. These findings demonstrate that Nagel bioceramics, produced with high crystallinity through the MSS method, are highly promising as 3D-printed biomaterials for applications in bone tissue regeneration.