Design and preparation of nanoporous Ag-Cu alloys by dealloying Mg-(Ag,Cu)-Y metallic glasses for antibacterial applications

Three-dimensional nanoporous Ag-Cu alloys with an atomic ratio of Ag to Cu varying from 0 to 1.0 were fabricated by dealloying Mg-(Ag,Cu)-Y metallic glass precursors in 0.04 M H₂SO₄ aqueous solution. Supersaturated Ag(Cu) solid solution in the nanoporous structure was obtained with a high Cu concentration (up to 47.4%) in the fcc Ag phase after the dealloying treatment. The nanoporous alloys with an ultrafine ligament size (down to 20 nm), a large specific surface area (up to 11.18 m² g^-1) and high oxidation resistance in air atmosphere were employed for inhibiting the growth of Gram-negative E. coli and Gram-positive S. aureus. In vitro characterization reveals that the nanoporous alloy with an Ag/Cu ratio of 1:1 exhibited the best antibacterial activities in terms of both ultralow minimal inhibitory concentration (MIC) (down to 3 and 2.5 mg L^-1 for S. aureus and E. coli) and long-term inhibition on bacterial growth in the group of the tested materials. A highly efficient and sustainable release of Cu ions from the nanoporous Ag-Cu alloy could be responsible for such excellent antibacterial activities.