Enhanced mechanical properties and anti-washout of calcium phosphate cement/montmorillonite composite bone-cement for bone-repair applications

Calcium phosphate cement (CPC) has received extensive attention as a filler for heteromorphic bone defects owing to its excellent biocompatibility, self-curing property, and degradability. However, the low strength and poor anti-washout properties still restrict the use of CPC in the clinical application. In this study, montmorillonite (MMT) was introduced into CPC to prepare CPC/MMT composite bone-cement. The compressive strength of the composite cement was synergistically enhanced by increasing intermolecular bonding and the impeding crack propagation. Owing to its unique lamellar structure, viscosity, and hydrophilicity, CPC bound to MMT via the bridging effect of water molecules and the electrostatic interaction between MMT and Ca²⁺. When subjected to an applied load, crack propagation was further hindered by MMT pull-out, load transfer, crack deflection, crack branching, and crack bridging, which consuming more fracture energy, significantly improving the compressive strength of the cement strength. At 50 wt% MMT addition, the compressive strength of the composite bone cement (CPC+50%MMT) was 48.5 MPa, which is 227.04% higher than that of CPC alone (14.83 MPa). Surprisingly, the anti-washout ability of CPC was significantly improved, as indicated by the decrease in the mass loss of the composite bone cement from 71.25 to 6.48%, overcoming the trade-off between strength and anti-washout properties. The final setting time was shortened from 22 to 11.37 min, and the injectability exceeded 90%. In addition, the composite bone cement demonstrated outstanding cell adhesion and proliferation abilities, making it a promising material for bone-repair therapy.