Harnessing eco-friendly synthesis: the in vitro bioactivity and biocompatibility of ceramic spinels

Harnessing a sustainable, starch-assisted gel synthesis, researchers have engineered MnAl₂O₄ and ZnAl₂O₄ spinel ceramics, calcined at 1000 °C, as next-generation bioactive materials. Comprehensive characterization via XRD and FTIR confirmed phase-pure crystallinity, while advanced FE-SEM/EDX and DLS analyses unveiled a pivotal divergence in their physical landscapes: MnAl₂O₄ emerged with a distinctive nanoscale architecture and a richer surface hydroxyl population compared to its ZnAl₂O₄ counterpart. This fundamental difference in surface chemistry and morphology directly translated to superior performance in simulated physiological environments. During in vitro bioactivity tests in simulated body fluid, both ceramics fostered essential calcium-phosphate layers, yet MnAl₂O₄ demonstrated markedly accelerated apatite nucleation, achieving a Ca/P ratio nearing that of ideal bone mineral (stoichiometric hydroxyapatite), alongside enhanced microstructural densification. Mechanically, it exhibited a robust, time-dependent increase in compressive strength, outperforming ZnAl₂O₄. Critically, biocompatibility assessment on human dermal fibroblasts revealed that MnAl₂O₄ maintained excellent cytocompatibility across all concentrations and exposure periods. In contrast, ZnAl₂O₄ induced mild, time-dependent cytotoxic effects. Collectively, these findings position MnAl₂O₄ spinel not merely as a compatible material, but as a highly promising and bioactive ceramic candidate poised to advance the field of bone graft substitutes and orthopedic implants.