A comparative study of synthetic and natural hydroxyapatite reinforcements in biodegradable magnesium–silver composites

Biodegradable magnesium composites are attractive materials for bone implant applications. This study compares synthetic (HAS) and natural (HAN) hydroxyapatite reinforcements in Mg1Ag composites regarding mechanical and corrosion performance. Microstructural analysis showed that reinforcements were distributed along grain boundaries as secondary phases. The addition of 10 wt-% HAS increased the hardness by 23.6%. Higher compressive strength was achieved with 5-10 wt-% HAN, reaching 187 MPa (65% improvement over Mg1Ag), while 5 wt-% HAS improved strength by ∼ 9% and enhancing ductility. Corrosion results indicated 15 wt-% HAS and HAN composites exhibited the most anodic E ocp (+36 mV and +31 mV vs. Mg1Ag). Potentiodynamic analysis identified 15 wt-% HAS as the most corrosion resistant ( E corr : − 1210 mV, i corr : 127 μA), whereas HAN composites showed higher i corr (>304 μA) than the Mg1Ag. Finally, MTT assays confirmed all composites are cytocompatible with Saos-2 cells, showing no significant cytotoxic effects.