A Bone Glue with Sustained Adhesion under Wet Conditions

Bone glues often suffer from low adhesion to bone under wet conditions. This study aims to improve wet adhesiveness of a bone glue based on a photocurable poly(ethylene glycol) dimethacrylate matrix through in situ interpenetrating network formation by addition of six‐armed isocyanate functional star‐shaped prepolymers (NCO‐sP(EO‐stat‐PO)). Biodegradable ceramic fillers are added to adjust the paste workability. The 3‐point bending strength of the bone glues is in the range of 3.5–5.5 MPa and not significantly affected by the addition of NCO‐sP(EO‐stat‐PO). Storage in phosphate buffered saline (PBS) decreases the bending strength of all formulations to approximately 1 MPa but the adhesion to cortical bone increases from 0.15–0.2 to 0.3–0.5 MPa after adding 20–40 wt% NCO‐sP(EO‐stat‐PO) to the matrix. Bone glues without the NCO‐sP(EO‐stat‐PO) additive lose their adhesiveness to bone after aging in PBS for 7 days, whereas modified glues maintain a shear strength of 0.18–0.25 MPa demonstrating the efficacy of the approach. Scanning electron microscopy and energy‐dispersive X‐ray spectroscopy investigations of the fracture surfaces prove a high amount of residual adhesive on the bone surface indicating that adhesion to the bone under wet conditions is stronger than cohesion. This study presents a strategy for preparing bone adhesives with improved wet adhesion. Isocyanate chemistry is transferred to bone adhesives by using cytocompatible hexa‐isocyanate‐functional macromolecule as additive to a poly(ethylene glycol) dimethacrylate matrix. This results in formation of interpenetrating networks; mechanical testing reveals an improved bone adhesive shear strength and cohesive failure in wet environment.