Biocompatibility Comparison of Stainless Steel, Gold-Coated, and Heat-Treated Gold-Coated Endovascular Stents
- PDF / 426,375 Bytes
- 6 Pages / 612 x 792 pts (letter) Page_size
- 61 Downloads / 200 Views
Biocompatibility Comparison of Stainless Steel, Gold-Coated, and Heat-Treated GoldCoated Endovascular Stents Alisa S. Morss, Philip Seifert, Adam Groothius, Danielle Bornstein, Campbell Rogers, Elazer R. Edelman Harvard-M.I.T. Division of Health Sciences and Technology Massachusetts Institute of Technology Cambridge, MA 02139 ABSTRACT Endovascular stents can be altered to improve radioopacity by applying a gold coating. We examined the vascular response in porcine coronary arteries to implantation of 9 mm NIR® stents that were either left intact, gold-coated, or heat-treated following gold coating. Our results show that while gold coating exacerbates neointimal hyperplasia and the inflammatory response, heat treatment removes this negative effect. Heat treatment was shown to increase the diffusion at the gold-steel interface and reduce the surface roughness. INTRODUCTION Endovascular coronary stents are widely used as the intervention of choice for the relief of arterial obstructive disease. As new designs and drug therapies have reduced thrombosis and restenosis rates, attention has turned to increasing ease of use [1]. Accurate stent placement can be made significantly easier for the interventional cardiologist by increasing stent radioopacity. However, this must be achieved without compromising functionality or biocompatibility. Gold coating has been suggested as a method to increase radioopacity, as gold is easy to work with and has been proven biocompatible in other applications. However, recent reports document an exaggerated vascular response to gold-coated stents [2]. The goal of this study was to determine the biological response to gold-coated stents and to determine if thermal postprocessing of the coated stents could alter biocompatibility. EXPERIMENTAL METHODS Seven cell stainless steel NIR® stents (Medinol, Ltd., Israel) 9 mm in length were left intact or coated with 7 ± 2.5 µm of gold. A two-step plating process, including the generation of a “seed layer,” was used to optimize adherence of the gold prior to laying down a plating layer. The gold plating increased the thickness of the struts by twice the coating depth. In a separate experiment, stent struts were electropolished prior to plating to negate this effect. A set of the gold-coated stents was heat-treated to determine the effect of thermal post-processing. The specific heat treatment process is proprietary to the stent manufacturer. The surface of the gold-coated and heat-treated gold-coated stents was analyzed using scanning electron microscopy (SEM, Leo 438VP) to visualize the stent surface morphology. Surface topography was then determined with atomic force microscopy (AFM, Topometrix Explorer) of 10 µm by 10 µm areas. Elemental analysis to examine the outermost surface composition was performed using Auger Electron Spectroscopy (PHI 660). Elemental analysis was performed on epoxy resin embedded stents with SEM in concert with a backscatter detector FF1.9.1
(Leo 400 Centaurus BSD) and Energy Dispersive X-Ray Spectroscopy (EDS, IXRF Analyz
Data Loading...
