Exploring the potential of Mg-Zn-Mn-Ca/ZnO composites as a biodegradable alternative for fracture fixation: microstructural, mechanical, and in-vitro biocompatibility analysis

Abstract

The current research investigates the microstructural, mechanical, in vitro degradation, biocompatibility, and in silico biomechanical behaviour of highly alloyed Mg-Zn-Mn-Ca quaternary system reinforced with ZnO nanopowder as candidate material for resorbable fixation devices. The as-cast composite materials showed dendritic microstructure comprising of α-Mg as major constituent and Mg7Zn3 and Ca2Mg6Zn3 phases distributed in interdendritic zones, as revealed by X-ray diffraction and scanning electron microscopy with energy dispersive X-ray spectroscopy. The addition of ZnO led to a 17% and 22% increase in ultimate and yield strengths in tension and a 24% and 27% enhancement in ultimate compressive and compressive yield strengths, respectively. The mechanical strengthening and observed tension–compression reversed yield asymmetry strongly correlated with the lattice distortion (c/a ratio) resulting from the macroalloying. The amplitude-dependent internal friction confirmed the presence of immobile obstacles to dislocations and their role through their hysteretic-type anelastic response. The in vitro degradation results revealed corrosion barrier effect of secondary phases. The cell adhesion, viability, and cytoskeleton observations favoured their biocompatibility except for hemolysis rate. The finite element results showed reduced stress-shielded zone for developed materials indicating the favourable mechanical environment for peri-implant tissues at fracture interface required for faster fracture healing.