Degradation, Cytotoxicity, and Antibacterial Properties of Fe-Mg Powders in Simulated Body Fluids

Abstract

Bioabsorbable metals offer great promise for temporary medical implants. Among them, iron (Fe) and magnesium (Mg) alloys are of particular interest due to their biocompatibility, mechanical properties, and degradation behavior. However, Fe degrades too slowly, while Mg degrades too quickly. Combining both elements has been proposed to overcome these drawbacks, though their immiscibility presents a processing challenge. In this study, Fe-5 wt.% Mg powder was produced via high-energy ball milling (Fe5Mg-BM), and its degradation was compared with pure Fe (Fe99) and milled Fe (Fe-BM). In vitro degradation was evaluated in three simulated body fluids: phosphate-buffered saline (PBS), modified Hanks´ balanced salt solution (HBSS), and Dulbecco´s Modified Eagle Medium (DMEM). Ion release, pH changes, and degradation products were characterized, along with cytotoxicity and antibacterial activity. The results showed that Fe5Mg-BM exhibited accelerated degradation compared to Fe99 and Fe-BM. Among the media, modified HBSS induced the greatest diversity and quantity of degraded compounds. Ion analysis revealed negligible iron release in PBS and HBSS, with the highest levels in DMEM for Fe5Mg-BM. Magnesium release followed the trend: PBS < DMEM < HBSS. Fe5Mg-BM showed limited cytotoxicity at 3 days and enhanced antibacterial activity in PBS and HBSS compared to Fe-BM. These results indicate that the biological effects arise from complex interactions at the material interface and the solubility of degradation products, suggesting that Mg is a promising alloying element for enhancing the performance of Fe-based materials in biomedical applications.