Antibakterielle, biologisch abbaubare Mg-Ag-Legierungen

The use of magnesium alloys as degradable metals for biomedical applications is topic of ongoing research. As a further aspect, the demand for multifunctional materials is increasing. Hence, binary Mg-Ag alloys were designed to combine the favourable properties of magnesium with the wellknown antibacterial property of silver. In this study, three Mg-Ag alloys, Mg2Ag, Mg4Ag and Mg6Ag which contain 1.87%, 3.82% and 6.00% silver by weight respectively were casted and processed with solution and aging heat treatment. Afterwards, the samples were investigated in vitro for metallographic, mechanical, corrosive, cytocompatible and antibacterial properties. The metallurgical analysis and phase identification showed that all alloys contained Mg4Ag as the dominant second phase. The mechanical properties of the Mg-Ag alloys were dramatically improved in several parameters especially after heat treatment. Corrosion tests revealed that after heat treatment, content of silver reduced the corrosion rate and exhibited less susceptibility to pitting corrosion than pure magnesium. Mg(OH)2 and MgO presented as main magnesium corrosion products while AgCl was found as the primary silver corrosion product. Immersion tests demonstrated that content of silver did not significantly shift the pH, osmolality and magnesium ion release in the environment. Cultivation and cytotoxicity tests with both primary cells and cell lines revealed that Mg-Ag alloys induce no negative effect on cells and show minor cytotoxicity. Antibacterial testing in a dynamic bioreactor system proved the alloys to reduce the viability of two common pathogenic bacteria, Staphylococcus aureus and Staphylococcus epidermidis. In summary, biodegradable Mg-Ag alloys are cytocompatible biomaterials with adjustable mechanical and corrosion properties while having sound antibacterial ability