Antibacterial effect of Ti-Ag alloy motivated by Ag-containing phases

The precipitates in Ti-Ag alloy made an important contribution to antibacterial activity. In order to study this specific effects, Ti-Ag samples with different forms of precipitates were produced by powder metallurgy and ingot metallurgy followed by heat treatment: Ti-Ag(T4) with no precipitate, Ti-Ag(as-cast) and Ti-Ag(T6) with Ti2Ag and Ti-Ag(PM) with Ti2Ag and Ag-rich phase. Microstructure was analyzed by scanning electronic microscope (SEM), and the antibacterial effects, expression of reactive oxygen species (ROS), protein leakage and biocompatibility were investigated by plate count method, staining technology and cell test. The antibacterial ability was in the following order from low to high: Ti-Ag(T4) < Ti-Ag(as-cast) < Ti-Ag(T6) < Ti-Ag(PM). It was elucidated that Ag-containing phase was the major controlling factor of Ti-Ag antibacterial property and Ti-Ag (PM) with micro-size Ti2Ag and Ag-rich phase exhibited high antibacterial activity. It was proposed that the existence of Ag-containing phases induced high expression of ROS in bacteria, which destroyed the homeostasis of the bacteria and eventually leads to the rupture of the bacterial membrane. Cell test indicated that Ti-Ag samples had no adverse effect on cells and had good biocompatibility.