One-step solid phase reaction-induced hydroxyapatite/magnesian whitlockite bioceramics for enhanced bone regeneration

Regenerative bioceramics for bone repair require an optimal balance of mechanical properties and osteogenic activity. Achieving this dual enhancement remains a significant challenge, particularly regarding the intrinsic properties of the ceramic. This study introduces a one-step solid-phase reaction strategy to generate new phase and nanostructure to enhance the performance of hydroxyapatite (HA) ceramic for bone repair. By incorporating magnesium phosphates (MP), the new phase (magnesian whitlockite, MWH) was produced, which exhibit suitable Mg²⁺ release and degradation efficiency compared to pure HA. The formation of interlaced nanocrystalline structure significantly improved the mechanical properties of the ceramics through a 'grain binding strengthening' mechanism, facilitating a transition from intergranular to transgranular fracture modes. Furthermore, MWH crystals with better strength than HA, contributed to the overall mechanical performance, ensuring compatibility with the mechanical requirements of bone implantation. The favorable release kinetics of Mg²⁺ promoted adhesion, spreading, and osteogenic differentiation of bone marrow stromal cells (BMSCs). In vivo studies validated the satisfactory bone regeneration capabilities of HA/MWH bioceramics. This innovative approach achieves a synergistic enhancement of mechanical strength and osteogenic activity, providing valuable insights for the optimization of porous bioceramics and their application in bone regeneration. STATEMENT OF SIGNIFICANCE: We present an innovative method to conveniently improve the synergistic performance of both mechanical strength and osteogenic activity in bioceramics. A one-step solid phase reaction was developed to produce Hydroxyapatite (HA)/Magnesian Whitlockite (MWH) dual-phase bioceramics, which exhibit superior mechanical properties over popular HA bioceramics. And the more favorable functional Mg²⁺ release kinetics of MWH resulted in a marked enhancement of osteogenic properties. We conducted experiments, computer simulations, cellular and animal evaluations to meticulously investigate the interlaced nanocrystalline structure, the 'grain binding strengthening' mechanisms of mechanical enhancement, and the improvement of osteogenic properties. Our work covers the entire spectrum of material science, preparation techniques, and biological performance validation. It provides new scientific insights for the research of porous bioceramics and would promote their applications in bone regeneration.