Bioactive and Biocompatible Nacre-like Apatite-Wollastonite/Polymer Composites with Enhanced Toughness and Load-Bearing Capability

This study investigates the development and characterization of apatite-wollastonite (AW) strong bioactive glass-ceramics combined with a polymer phase to create nacre-like composites for potential use as load-bearing bone implants. The results indicate that the maximum ceramic fraction that maintains the nacre-like structure is about 70 vol%. These composites are stronger and tougher than natural bone, with a matching Young’s modulus, making them suitable candidates for load-bearing bone implants. The maximum flexural strength and fracture toughness of these composites are approximately 196 ± 4 MPa and 10 MPa.m1/2, respectively. Additionally, the Young’s modulus of the composites is 23 ± 4 GPa, closely matching that of natural bone, which can potentially reduce the stress-shielding issues associated with commercial metal implants, such as titanium.

In situ microstructural characterization during fracture toughness experiments revealed that the composites exhibit various extrinsic toughening mechanisms, such as crack deflection, frictional sliding, and pull-out of ceramic walls, leading to a rising R-curve behavior in the composites. Furthermore, bioactivity tests demonstrate the formation of a biologically relevant apatite layer on the composite surface. The biomaterial confers no significant acute cytotoxicity or affect upon cellular proliferation, indicating the cytocompatibility of the composite. These findings suggest that the bioactive nacre-like AW/polymer composites possess exceptional mechanical properties and cytocompatibility, making them promising candidates for load-bearing bone implants.