Biodegradable, elastomeric coatings with controlled anti-proliferative agent release for magnesium-based cardiovascular stents

Abstract

Vascular stent design continues to evolve to further improve the efficacy and minimize the risks associated with these devices. Drug-eluting coatings have been widely adopted and, more recently, biodegradable stents have been the focus of extensive evaluation. In this report, biodegradable elastomeric polyurethanes were synthesized and applied as drug-eluting coatings for a relatively new class of degradable vascular stents based on Mg. The dynamic degradation behavior, hemocompatibility and drug release were investigated for poly(carbonate urethane) urea (PCUU) and poly(ester urethane) urea (PEUU) coated magnesium alloy (AZ31) stents. Poly(lactic-co-glycolic acid) (PLGA) coated and bare stents were employed as control groups. The PCUU coating effectively slowed the Mg alloy corrosion in dynamic degradation testing compared to PEUU-coated, PLGA-coated and bare Mg alloy stents. This was confirmed by electron microscopy, energy-dispersive x-ray spectroscopy and magnesium ion release experiments. PCUU-coating of AZ31 was also associated with significantly reduced platelet adhesion in acute blood contact testing. Rat vascular smooth muscle cell (rSMC) proliferation was successfully inhibited when paclitaxel was released from pre-loaded PCUU coatings. The corrosion retardation, low thrombogenicity, drug loading capacity, and high elasticity make PCUU an attractive option for drug eluting coating on biodegradable metallic cardiovascular stents.

In Vitro and In Vivo Testing of Zinc as a Biodegradable Material for Stents Fabricated by Photo-Chemical Etching

“…Our patented alternative is based on photo-chemical etching to transfer a pattern of the stent struts onto a Mg sheet [13]. This type of Mg stent has been characterized in vitro and the results are published elsewhere [14][15][16][17][18][19]. In this study, we demonstrate that photo-chemical etching can be used to create stent materials out of pure Zn and that these materials are well tolerated by tissues in an initial in vivo study.…”

The effect of tensile and fluid shear stress on the in vitro degradation of magnesium alloy for stent applications

“…However, concerns have been raised about their permanently presence in blood vessels, such as late stent thrombosis, neointimal hyperplasia, and in-stent restenosis. Biodegradable stents may overcome these drawbacks, which can provide sufficient but temporary support scaffolding the blood vessels [2,3]. Magnesium based stents show great potential to be an intriguing alternative to permanent stents due to the adequate mechanical properties, good biocompatibility and biodegradability [4,5].…”

The Surface Modification Methods for Constructing Polymer-Coated Stents

“…However, the fast decomposition rate and accumulation of hydrogen gas upon degradation severely limit their clinical application [22]. Clearly, controlling the corrosion rate is required to make use of magnesium and its alloy materials feasible for surgical implantation.…”

“…Among them, polymer coating not only is potential to corrosion resistance, but also can act as a drug reservoir [3,27,28]. More importantly, this technique holds the ability to be functionalized with various biomolecules including poly(lactic-co-glycolic acid) and poly(l-lactide) acid [22]. In brief, polymer coating metallic stents are having the aim to "encapsulate" the substrate in order to hinder the possible postoperative adverse effects caused by implant devices [29][30][31].…”