Antibacterial Activity of a Trace-Cu-Modified Mg Alloy in Simulated Intestinal Fluid

Mg alloys hold promise for biodegradable gastrointestinal implants, but most evaluations rely on simplified media like Hank's solution, which lacks organic components and fails to replicate the acidic-to-alkaline transition of intestinal fluid, risking underestimation of biodegradation rates and clinical relevance. This work investigated a trace-Cu-modified Mg alloy (Mg-0.05Cu) in simulated intestinal fluid (SIF) versus Hank's solution. Microstructural analysis confirmed Mg₂Cu intermetallic phases as Cu reservoirs. Electrochemical and immersion tests revealed significantly accelerated biodegradation in SIF, due to its disruption of protective layer formation, sustaining loose biodegradation products. The biodegradation rate of the trace-Cu-modified Mg alloy in SIF was consistent with reported values for Mg alloys in similar media, as was that in Hank's solution. Remarkably, Mg-0.05Cu exhibited potent antibacterial activity against E. coli, achieving 99.3% eradication within 12 h and 100% elimination by 24-48 h, alongside excellent cytocompatibility with L929 cells (>95% viability). This efficacy arose from the synergistic Cu²⁺ release and high-pH microenvironment. These findings demonstrate that trace Cu alloying in high-purity Mg balances rapid antibacterial action with controlled biodegradation in a physiologically relevant SIF. This positions Mg-0.05Cu as a highly promising candidate for practical applications, such as biodegradable intestinal stents, anti-adhesion barriers, anastomosis rings, and anti-obesity devices, where rapid infection control and predictable degradation are critical for clinical success. This work underscores the importance of using biomimetic media for evaluating gastrointestinal implants and establishes Mg-0.05Cu as a promising strategy for developing infection-resistant biodegradable devices.