Exploring optimal Cu content in SLMed Fe-30Mn alloys for orthopedic application: Tailored accelerated biodegradation, antibacterial activity, and cytocompatibility

Abstract

Biodegradable Fe-based alloys for orthopedic implants suffer from excessively slow physiological degradation. Although Cu alloying can accelerate corrosion and impart antibacterial activity, the optimal Cu content balancing degradation kinetics, mechanical integrity, wear resistance, and biocompatibility remains a critical challenge. This work comprehensively evaluated selective laser melted (SLMed) Fe-30Mn-xCu (x = 0-12 wt%) for orthopedic implants, revealing the critical role of Cu content in overall performance. Increasing Cu content refined grains and initially enhanced hardness, compressive strength, and wear resistance, peaking at 10 wt% Cu. Crucially, biodegradation kinetics peaked at 8 wt% Cu, evidenced by the most negative corrosion potential, highest corrosion current density, and smallest capacitive loop diameter. This is attributed to a balance between micro-galvanic corrosion acceleration and the barrier effect of forming degradation products/passive films. SLMed Fe-30Mn-xCu (x ≥ 8 wt%) demonstrated exceptional antibacterial activity (>99.9% inhibition against S. aureus and E. coli) due to sustained Cu²⁺ release, along with excellent cytocompatibility with MC3T3-E1 cells. This synergy of accelerated degradation, antibacterial efficacy, and biocompatibility, along with appropriate mechanical and wear properties, identifies 8 wt% Cu as optimal for degradation- and infection-dominant applications, and 10 wt% Cu as optimal for load-bearing scenarios. This work demonstrates that microstructural tailoring via SLM achieves accelerated degradation, antibacterial efficacy, and biocompatibility, offering a promising strategy for patient-specific infection-resistant bone repair.