Injectable trimagnesium phosphate-filled magnesium potassium phosphate cement with improved handling properties, high early strength, and low heat release for bone defect repair

Magnesium phosphate cement (MPC) has emerged as a promising biomaterial in preclinical studies for orthopedic applications, particularly in bone defect repair, due to its rapid setting properties and high mechanical strength. However, excessive MgO in MPCs accelerates the setting and heat release, which necessitates an increased liquid-to-powder ratio (LPR) that compromises strength, ultimately making it difficult to reconcile the performance metrics of processability, heat release, and mechanical strength. In this study, trimagnesium phosphate-magnesium phosphate cement (TM-MPC) was developed by replacing excess MgO with chemically stable trimagnesium phosphate (Mg₃(PO₄)₂, TMP) at a low LPR (down to 0.20 mL/g, PLR = 5 g/mL). This strategy resulted in the formation of cement material system with suitable setting time (10-12 min), low curing temperature (<47°C), remarkable early compressive strength (131.25 ± 29.39 MPa), near physiological pH, and good injectability (6-9 min), which could address the critical drawbacks of traditional MPCs. In vitro evaluations showed acceptable cytocompatibility in MC3T3-E1 cells. Based on heat evolution and characterization of early hydration products, reducing the LPR was found to retard initial hydration and attenuated exothermic heat release. This work provides a facile and effective strategy for engineering high-performance bone cements with improved processability, which offers a design paradigm for future MPC systems in specific biomedical applications.