Hydrostable hard tissue adhesives based on organophosphates and magnesium phosphates with strong bonding and cellular compatibility

Bone adhesives have significant potential for improving surgical procedures and can enhance and simplify them. Recently, phosphoserine-modified mineral-organic resorbable bone adhesives have shown particular promise. Among them, MgO/MgP-based cement exhibit high adhesive strength but suffer from water instability. This study introduces mineral-organic hard tissue adhesives based on organophosphates and magnesium phosphate with hydrolytic stability to enable cell testing. Amorphised magnesium phosphates enhanced reactivity, eliminating MgO additives. Alongside the established organophosphate phosphoserine (OPLS), sodium phytate was investigated as an alternative. We performed comprehensive mechanical and material characterizations, complemented by in vitro cytocompatibility assessments using osteoblastic MG-63 cells and osteoclastic RAW 264.7 cells differentiated with RANKL. Sodium phytate demonstrated strong adhesive properties, with an initial shear strength of 4.35 ± 0.86 MPa, retaining 1.3 ± 0.27 MPa after 7 days. However, it showed lower cytocompatibility with MG-63 cells than with OPLS. The OPLS/MgP combination exhibited both favorable cytocompatibility and strong adhesive performance, achieving an initial shear strength of 3.87 ± 0.53 MPa and maintaining 2.19 ± 0.69 MPa after 7 days. These findings underscore the potential of organophosphate-magnesium compound cement as viable candidates for mineral-organic hard tissue adhesives in surgical applications, combining excellent adhesive properties with favorable cytocompatibility.