Antibacterial biodegradable Mg-Ag alloys

Abstract

The use of magnesium alloys as degradable metals for biomedical applications is a topic of ongoing research and the demand for multifunctional materials is increasing. Hence, binary Mg-Ag alloys were designed as implant materials to combine the favourable properties of magnesium with the well-known antibacterial property of silver. In this study, three Mg-Ag alloys, Mg2Ag, Mg4Ag and Mg6Ag that contain 1.87 %, 3.82 % and 6.00 % silver by weight, respectively, were cast and processed with solution (T4) and aging (T6) heat treatment.The metallurgical analysis and phase identification showed that all alloys contained Mg4Ag as the dominant β phase. After heat treatment, the mechanical properties of all Mg-Ag alloys were significantly improved and the corrosion rate was also significantly reduced, due to presence of silver. Mg(OH) 2 and MgO present the main magnesium corrosion products, while AgCl was found as the corresponding primary silver corrosion product. Immersion tests, under cell culture conditions, demonstrated that the silver content did not significantly shift the pH and magnesium ion release. In vitro tests, with both primary osteoblasts and cell lines (MG63, RAW 264.7), revealed that Mg-Ag alloys show negligible cytotoxicity and sound cytocompatibility. Antibacterial assays, performed in a dynamic bioreactor system, proved that the alloys reduce the viability of two common pathogenic bacteria, Staphylococcus aureus (DSMZ 20231) and Staphylococcus epidermidis (DSMZ 3269), and the results showed that the killing rate of the alloys against tested bacteria exceeded 90%. In summary, biodegradable Mg-Ag alloys are cytocompatible materials with adjustable mechanical and corrosion properties and show promising antibacterial activity, which indicates their potential as antibacterial biodegradable implant materials.

Intramedullary Mg2Ag nails augment callus formation during fracture healing in mice

“…These findings are consistent with those reported by others and are in support of further investigating this novel material in musculoskeletal research [25,26,31].…”

“…Recently, members of our consortium reported a novel Mg alloy containing 2% silver (Mg2Ag), which was cast and treated by a solidification cooling process, resulting in appropriate mechanical properties and a rather low degradation rate. Furthermore, in vitro investigations of this alloy showed favorable antibacterial effects and no cytotoxicity to human osteoblasts [25].…”

Zn-Mg and Zn-Ag Degradation Mechanism Under Biologically Relevant Conditions

“…Silver in itself is cytotoxic, but low amounts of silver as an alloying element have been suggested to be beneficial for imparting antibacterial properties to implants. 34 Enrichment of silver on the surface with time may, however, shift the initially beneficial antibacterial properties toward cytotoxic properties as the silver concentration increases. Such changes may complicate the healing process.…”

Biodegradable Metallic Wires in Dental and Orthopedic Applications: A Review

“…The combination of Mg with rare earth metals decreased the corrosion rate but also created cytotoxic effects [97,99]. Tie et al [112] introduced a novel Mg alloy containing 2% silver (Mg2Ag) and showed that the alloy possessed appropriate mechanical properties and a rather low degradation rate in vitro. In order to assess the in vivo behavior of the alloy, Jahn et al [113] implanted Mg2Ag intramedullary wires into mice with and without a femoral shaft fracture.…”