Evaluation of magnesium-based scaffolds fabricated using a modified sintering technique and two types of space holding agents (in vitro study).

Objective: The aim of this work was to study the mechanical, degradation behavior and bioactivity of porous magnesium-based scaffolds alloyed with zinc and hydroxyapatite, fabricated using two different types of space holding agents and a modified powder metallurgy route.

Methods: Powder particles of magnesium, zinc, hydroxyapatite (HA) and spacers were mixed, then mixtures were divided into 6 groups: IA (urea/0%HA), IB (urea/5%HA), IC (urea/7.5%HA), IIA (ammonium bicarbonate/0%HA), IIB (ammonium bicarbonate/5%HA) and IIC (ammonium bicarbonate/7.5%HA). A modified powder metallurgy route was used to fabricate the composites. Porosity analysis and microstructural characterization using Scanning Electron Microscope (SEM), Energy Dispersive X-ray Analysis (EDX), and X-ray Diffraction Analysis (XRD) were done. Evaluation of mechanical properties, in-vitro degradation rate in simulated body fluid (SBF) and in-vitro bioactivity using SEM and XRD were done. Data were statistically analyzed using two-way and three-way repeated ANOVA tests.

Results: All scaffolds were found to be highly porous. Significant differences were observed regarding mechanical properties, degradation rate and concentration of magnesium released during degradation (P  < 0.0001). The results showed that group IIB had the lowest strength and fastest corrosion rate, while IB had the highest strength and elastic modulus and the slowest corrosion rate among all groups. Bioactivity evaluation revealed extensive formation of calcium phosphate crystals and precipitations covering the scaffolds' surfaces.

Conclusion: This study showed that using up to 5% HA as a reinforcing element with moderate compaction pressure and urea as a space holding agent can result in the fabrication of magnesium scaffolds suitable for orthopedic applications.