Modulation of zinc oxide-tricalcium phosphate microstructure, hardness, and cell-viability through controlled magnesium oxide incorporation

Synthetic calcium phosphate-based biomaterials have been used over the past decades in medical applications such as bone tissue repair, reconstruction, and replacement. In the present study, the sintering process, phase relationships, microstructure, hardness, and adjusted biodegradation rates, toxicity, and cytocompatibility of zinc oxide-tricalcium phosphate (ZnO-TCP) biomaterials tuned with magnesium oxide (MgO) were investigated for the first time. Specifically, 1 wt% ZnO-TCP (1Z-TCP) biomaterials were modified by incorporating varying amounts of MgO to tailor their properties, positioning them as a promising alternative to pure TCP. In this study, 1Z-TCP biomaterials with MgO content ranging from 0.125 to 1.0 wt% were obtained via solid-state reaction sintering. The effects of MgO on densification, microstructural characteristics, hardness, and Young's modulus of 1ZnO-xMgO-TCP (1Z-xM-TCP) biomaterials were systematically analysed. Subsequently, the “in vitro” solubility of the biomaterials in simulated body fluid was assessed, followed by in vitro cell culture experiments using MG63 osteoblast-like cells. The results indicated that the biomaterials studied were non-cytotoxic and exhibited favorable cell adhesion, proliferation, and differentiation, suggesting that both 1Z-TCP and 1Z-xM-TCP biomaterials promote improved cell-material interaction compared to pure-TCP. The results obtained provide a framework for designing 1Z-xM-TCP materials tailored to specific applications by enabling the tuning of degradation rate, mechanical properties, biological response, and cell viability through the controlled MgO incorporation.