Antibacterial activity and mechanism of newly developed Zr-30Ta and Zr-25Ta-5Ti alloys against implant-associated infection

Infection is a common problem after implantation, and the currently used Ti-based implants have insufficient antibacterial activities. The newly developed Zr-30Ta and Zr-25Ta-5Ti alloys exhibited good mechanical properties, low elastic moduli, and high corrosion resistance. In this work, their antibacterial activities and antibacterial mechanisms were investigated. The surface roughness, wettability, and charge of the alloys were evaluated using a profilometer, drop shape analyzer, and electrokinetic analyzer, respectively. The antibacterial activity against Streptococcus mutans and Porphyromonas gingivalis was investigated using the inhibition zone assay, plate count assay, live/dead staining, and scanning electron microscopy (SEM). The reactive oxygen species release (ROS) was evaluated using the 2'7'-dichlorodihydrofluorescein diacetate (DCFH-DA) assay. The results demonstrated that Zr-30Ta and Zr-25Ta-5Ti alloys had favorable smooth, hydrophilic, negatively charged surfaces that decreased bacteria adhesion and prevented biofilm formation. Zr-30Ta and Zr-25Ta-5Ti alloys also exhibited a time-dependent decrease in the bacteria adhesion and viability. Zr-30Ta and Zr-25Ta-5Ti alloys were also found to induce direct membrane damage and increase ROS production, resulting in significantly better antibacterial activities than CP-Ti. Zr-30Ta and Zr-25Ta-5Ti alloys exhibited comparable antibacterial activities. This work suggests that the newly developed Zr-30Ta and Zr-25Ta-5Ti alloys have good antibacterial activity against Streptococcus mutans and Porphyromonas gingivalis and are promising candidate materials for dental and orthopedic implants. Graphical abstract