Effect of TiO₂ doping on degradation rate, microstructure and strength of borate bioactive glass scaffolds

A titanium-containing borate glass series based on the system (52-X) B₂O₃-12CaO-6P₂O₅-14Na₂O-16ZnO-XTiO₂ with X varying from 0, 5 and 15 mol% of TiO₂ incorporated, identified as BRT0, BRT1 and BRT3, respectively, were used in this study. Scaffolds (pore sizes, 165-230 μm and porosity, 53.51-69.51%) were prepared using a polymer foam replication technique. BRT3 scaffolds exhibited higher compressive strength (7.16 ± 0.22 MPa) when compared to BRT0 (6.02 ± 0.47 MPa) and BRT1 (5.65 ± 0.28 MPa) scaffolds with lower, or no, TiO₂ content. The solubility of the scaffolds decreased as the TiO₂ content increased up to 15 mol% when samples of each scaffold were immersed in DI water and the pH of all these extracts went up from 7.0 to 8.5 in 30 days. The cumulative ion release from the scaffolds showed significant difference with respect to TiO₂ content; addition of 5 mol% TiO₂ at the expense of borate (B₂O₃) decreased the ion release remarkably. Furthermore, it was found that for all three scaffolds, cumulative ion release increased with incubation time. The results indicate that the degradation rates and compressive strengths of borate bioactive glass scaffolds could be controlled by varying the amount of TiO₂ incorporated, confirming their potential as scaffolds in TKA and rTKA.