Catalyst-enhanced micro-galvanic effect of Cu3N/Cu-bearing NiTi alloy surface for selective bacteria killing

NiTi alloy stent is widely applied to the treatment of coronary artery disease, however, stent associated bacterial infection may occur because of its lack of antibacterial ability. Endowing the selective antibacterial ability is promising for NiTi alloy but still remains a considerable challenge. Here, a novel NiTi alloy surface embedded with cuprous nitride/copper nanoparticles (Cu3N/Cu NPs) was constructed by sequential Cu and N plasma immersion ion implantation & deposition (PIII&D). First, the Cu atoms evenly nucleated and grew into Cu nanoparticles on the NiTi alloy surface during Cu PIII&D process followed by partially transforming to Cu3N by N PIII&D treatment. Due to the electrocatalysis of Cu3N, Cu and N PIII&D modified NiTi alloy surface demonstrated a catalyst-enhanced micro-galvanic effect, which produced excellent antibacterial abilities against both Gram-negative and positive bacteria. The antibacterial mechanism of Cu and N PIII&D NiTi alloy surface was verified to primarily correlate with the blocked ATP synthesis and oxidative stress of bacteria due to the overconsumption of protons and the production of reactive oxygen species (ROS) by continuous catalyst-enhanced micro-galvanic reaction. Meanwhile, this modified NiTi alloy surface showed an enhancement effect on the adhesion and proliferation of human umbilical vein endothelial cell. This study provides a new sight for how to endow implant with selective antibacterial ability.