Electrochemical and SEM Characterization of Gold-Coated Stents In Vitro

Abstract

The inert properties of gold make it a useful material for implants. Gold was applied as a coating on 316L stainless steel stents to improve the radiopacity and to provide better thrombogenic resistance and a lower degree of restenosis after deployment. Reports of clinical trials using gold-coated stents showed controversial results. A detailed examination of gold-coated stents was designed to understand the influence of surface conditions on the electrochemical properties in vitro. Corrosion resistance of gold-coated stents was investigated by cyclic polarization, and potentiostatic control. Surface morphologies of gold-coated stents in as-received condition, postinflated condition, and after cyclic polarization were characterized by scanning electron spectroscopy (SES). X-ray mapping identified elemental distribution. Results found severe defects in the gold-coating in the as-received condition, cracks and wrinkles on inflated gold-coated stents, and severe corrosion after cyclic polarization. Leaching of metallic ions in Ringer’s solution was possible.

Clinical device‐related article surface characterization of explanted endovascular stents: Evidence of in vivo corrosion

“…As a result, when accelerated corrosion testing was performed, the anodic 316L SS underlying the gold coating demonstrated considerable corrosion due to the difference in electric potential between the two materials. It has been suggested that these in vitro findings may have contributed to the significant restenosis associated with these stents in vivo 32…”

Coating induced corrosion of coronary stents - A comparative study with clinical consequences

“…Despite proving excellent corrosion behavior, Au coated stents resulted with high rates of restenosis [20]. Delamination of the Au coating, further exposition of the 316LSS substrate to the physiological medium and ultimate ion release due to corrosion of the implant were proposed to explain the poor outcome of Au coated stents [21]. Another studies revealed very high concentration of Au in the blood of patients implanted with Au coated stents when compared against patients implanted with Nitinol stents.…”

Ternary β and γ phases in the Al–Au–Cu system at 750°C

“…Spangold has many other properties that could make it useful as a shape memory alloy, including good castability, high strength and wear resistance, and good resistance to corrosion [16,17]. Also, it has two fundamental properties that make it ideal for use in biomedical implant applications: gold is biocompatible [18] and is radio-opaque due to its high atomic number (the latter feature facilitates the positioning or manipulation of a medical device in vivo) [19]. The major drawback of this material, however, is the 76 wt.% gold it contains, which would make the manufacturing cost high.…”