Abstract
Coronary artery disease (CAD) affects every fifth person in the world. The gold-standard treatment for CAD is stent implantation, however, the existing therapy is not sufficient. In recent years, titanium oxynitride (TiOxNy) coatings on bare metal stents (BMSs) attracted the attention of many researchers around the world due to their promising results and improved surface properties. However, good coating adhesion and coverage of the inner surface in stent applications is still a challenging task. Moreover, enhanced corrosion resistance and durability over a longer period under the influence of an aggressive biological environment is one of the main requirements while developing novel coatings for bare-metal stents. In this work, the titanium oxynitride (TiOxNy) coated stainless steel stents were fabricated by magnetron sputtering and the corrosion behavior of coated and uncoated stents has been studied using immersion, fluid dynamic, and electrochemical corrosion tests. For the first time, the entire stent surface has been used for quantitative corrosion tests on stents. We discuss and compare the in vitro biostability and corrosion behavior of bare stainless steel (316L) and titanium oxynitride films (TiOxNy) coated stents.TiOxNy coatings provide valuable stability to the BMS against harsh environments or conditions. The coated stents are remarkably more stable when compared with the reference uncoated stents (316L BMS), regardless of the ratio of O2 and N2. The variation of stent coating parameters is still possible to get more anticorrosive and biostable behavior; therefore, the results could provide the basis for further research.
Highlights
From the first stent used in medical practice by Jacques Puel and Ulrich Sigwart [1] and the first FDA approved bare metal stent (BMS) by Cesare Gianturco and Gary S
After 4 days of immersion, the mass variation was shifted to the negative direction again and this process continued until 7 days of immersion
After 7 days of immersion, the equilibrium was reached and the mass variation was constant for the whole immersion period of 28 days except for sample A which loses its mass spontaneously after the 21 days of immersion which could be due to pits formation and the release of ions which is supported by the release of titanium in ICPMS studies
Summary
From the first stent used in medical practice by Jacques Puel and Ulrich Sigwart [1] and the first FDA approved bare metal stent (BMS) by Cesare Gianturco and Gary S. Roubin [2], there is a significant progress in this filed and a wide variety of stents are available in the market including biodegradable stents, drug eluting stents, and coated stents. In order to avoid or minimize the risk of in-stent restenosis (ISR) in BMS and to improve the surface properties, various coatings have been developed Among the coated stents available on the market, titanium oxynitride coatings show promising clinical results. Current researches are focused on improving TiOxNy coating properties in order to reduce still significant restenosis rate. Several studies show the dependence of surface morphology, surface structure, wettability, and biocompatibility of TiOxNy coatings on the concentration ratio of oxygen and nitrogen as well as on deposition technology and its parameters [15]–[17]
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