Plasma treated NiTi stents for antithrombosis and antibacterial infection by ammonia generation and surface charge regulation

Interventional therapy represents the primary treatment modality for cardiovascular disease associated with vascular obstruction. However, conventional stents are susceptible to thrombosis and infection, leading to serious threats to patient health and, in some cases, mortality. In this study, a Ta/Ta 2 O 5 /Ni 3 N film was prepared in situ on the nitinol (Ni-Ti) stent using a sequential plasma immersion ion implantation method. As tantalum has a negative charge under physiological conditions and nickel nitride adsorbs protons in solution, the introduction of tantalum and nickel nitride is expected to allow the surface charge of the material to be tailor-made. The film displays excellent hemocompatibility and reduced platelet adhesion, based on the combined effect of “mosaic-like” charge distribution of the film and the high dispersion/polarity component ratio in the surface tension. Ammonia species is an important physiological signaling molecule, which could be produced by the affinity of nitrogen in nickel nitride with protons in solution. In turn, ammonia species modulates the cellular NRF2/HO-1 signaling pathway, thereby enhancing cell viability. Furthermore, ammonia species increases intracellular eNOS gene expression, which enhances cell migration and promotes early endothelialization. Additionally, the depletion of protons by nickel nitride can disrupt bacterial metabolism, which results in the production of reactive oxygen species (ROS) and nitric oxide (NO) within the bacteria, achieving a killing efficacy of over 99.9% for both gram-negative Escherichia coli and gram-positive Staphylococcus aureus . It is anticipated that this straightforward, multifaceted inorganic bioactive film approach will prove an invaluable solution for enhancing the reliability of stents and reducing the burden on patients.