Zn-alloy provides a novel platform for mechanically stable bioresorbable vascular stents.

Christoph Hehrlein,Vitus Stachniss,Ernst Nennig,Christoph Bode,Thomas Epting,Constantin Von Zur Mühlen,Harald Fischer,Jörg Haberstroh,Hans Schwarzbach,Adalbert Kovacs,Lilly Mey,Nadia Kress,Amina Arab,Björn Schorch,Stefanie Schiestel,Ralf Kinscherf,Donghui Zhu

doi:10.1371/journal.pone.0209111

Abstract

Metallic Zn alloys have recently gained interest as potential candidates for developing platforms of bioresorbable vascular stents (BVS). Previous studies revealed that Mg alloys used for BVS can degrade too early, whereas PLLA materials may fail to provide effective scaffolding properties. Here we report on results of a new bioresorbable, metallic stent made from a Zn-Ag alloy studied in a porcine animal model of thrombosis and restenosis. While the tensile strength (MPa) of Zn-3Ag was higher than that of PLLA and resembled Mg’s (WE43), fracture elongation (%) of Zn-3Ag was much greater (18-fold) than the PLLA’s or Mg alloy’s (WE43). Zn-3Ag exposed to HAoSMC culture medium for 30 days revealed degradation elements consisting of Zn, O, N, C, P, and Na at a 6 nm surface depth. Platelet adhesion rates and blood biocompatibility did not differ between Zn-3Ag, PLLA, Mg (WE43), and non-resorbable Nitinol (NiTi) stent materials. Balloon-expandable Zn-3Ag alloy BVS implanted into iliofemoral arteries of 15 juvenile domestic pigs were easily visible fluoroscopically at implantation, and their bioresorption was readily detectable via X-ray over time. Histologically, arteries with Zn-3Ag BVS were completely endothelialized, covered with neointima, and were patent at 1, 3, and 6 months follow-up with no signs of stent thrombosis. Zn-3Ag alloy appears to be a promising material platform for the fabrication of a new generation of bioresorbable vascular stents.

Highlights

Stents have become clinical routine worldwide as a standard of care to treat coronary atherosclerotic obstructions since their introduction by Jaques Puel 30 years ago [1]
Zn-3Ag material demonstrated higher tensile strength compared to poly-l-lactic acid (PLLA) and much higher fracture elongation rates than PLLA, WE43, or pure Zn (Table 1)
A recent clinical study in coronary arteries comparing the long-term results of bioresorbable PLLA stents with non-degradable metallic stents revealed the inferiority of PLLA stents versus metallic non-degradable stent platforms, causing more late lumen loss due to restenosis in the treated arteries [6]

Summary

Introduction

Stents have become clinical routine worldwide as a standard of care to treat coronary atherosclerotic obstructions since their introduction by Jaques Puel 30 years ago [1]. K.], but did not have any additional role in the study design, data collection and analysis, decision to publish, or preparation of the manuscript. The specific roles of these authors are articulated in the ‘author contributions’ section.”

Methods

Results

Conclusion