Multifunctional Y₂O₃-Modified Borotellurite Bioactive Glasses for Bone Tissue Engineering Applications

Developing bioactive glasses that simultaneously provide mechanical reliability, cytocompatibility, controlled ion release, and antibacterial functionality remains a major challenge in bone tissue engineering. In this study, borotellurite-based bioactive glasses with the composition (45 − x)TeO₂–20Na₂O–10CaO–15P₂O₅–10B₂O₃–xY₂O₃ (x = 0–7 mol.%) were designed to elucidate the role of Y₂O₃ in governing composition–structure–property relationships. Structural, thermal, mechanical, ion-release, bioactivity, cytocompatibility, cell-adhesion, and antibacterial properties were systematically evaluated, and the most promising composition was further modified by silver surface coating. Y₂O₃ incorporation markedly enhanced thermal stability, hardness, and fracture resistance, with hardness reaching 4.317 GPa at 7 mol.%, while the highest compressive strength was achieved at 1 mol.% Y₂O₃ (67.97 MPa). Importantly, Y₂O₃ regulated dissolution behavior and mitigated the severe long-term cytotoxicity of the undoped glass, maintaining all doped compositions above the ISO 10993-5 threshold after 30 days. Higher Y₂O₃ contents also promoted osteoblast adhesion and facilitated bioactive surface layer formation following SBF immersion. No detectable E. coli adhesion was observed, whereas the TBY3 composition exhibited the lowest S. aureus adhesion, further improved by silver coating. These results demonstrate Y₂O₃ as an effective multifunctional modifier for engineering mechanically robust, biologically favorable, and antibacterial borotellurite bioactive glasses for bone repair.