Drug‐Eluting Bioabsorbable Magnesium Stent

Abstract

Current stent technology is based on the use of permanent implants that remain life long in the vessel wall, far beyond the time required for the prosthesis to accomplish its main goals of sealing dissection and preventing wall recoil. With the possibility to implant long vessel segments using antiproliferative drugs to prevent restenosis, the practice of transforming the coronary vessels into stiff tubes with a full metal jacket covering all side branches and being unable to adjust to the long-term wall changes, including wall remodeling with lumen ectasia becomes a serious concern. In this article, we describe the first biodegradable stent based on a magnesium alloy that allows controlled corrosion with release to the vessel wall and the blood stream of a natural body component such as magnesium with beneficial antithrombotic, antiarrhythmic, and antiproliferative properties. We also discuss the animal experiments and the initial clinical applications in 20 patients with implants below the knee, with final results soon to be released, and the plans for the first coronary study. The results of these last two studies will indicate whether the absence of a permanent implant and the antiproliferative properties shown in animals are sufficient to prevent the restenotic process in humans or whether the prosthesis must be modified by adding the biodegradable coating with conventional antiproliferative drugs.

In vitroandin vivocorrosion properties of new iron–manganese alloys designed for cardiovascular applications

“…Pure iron stents were tested in different cellculture and animal models [10][11][12] and magnesium or magnesium-based alloy systems were implemented and tested in various in vitro and in vivo models. [13][14][15][16] Although the addition of antiproliferative drugs has recently proven to be beneficial in clinical trials with absorbable metal scaffolds, 17 to date, none of the approaches has reached routine clinical practice. Uncoated pure magnesium or magnesium based alloys exhibited ex stent restenosis and medial disruption leading to local adverse effects.…”

Histological and molecular evaluation of iron as degradable medical implant material in a murine animal model

“…The implants should be flexible to be compatible with minimally invasive techniques, and sufficiently sturdy to prevent collapsing or kinking. The mechanical stability of resorbable polymeric materials is not satisfactory and their degradation can provoke inflammation, whereas with metal alloys superior mechanical strength can be achieved [8][9][10][11][12][13][14][15][16][17][18][19][20][21][22][23][24] . Whereas magnesium stents tend to degrade too rapidly, this appears not to be the case for iron implants [25][26][27][28][29][30][31] .…”

Biodegradable stent

“…AE21 and WE43 among magnesium alloys are emerging as the cardiovascular stent material [22,23]. AE21 is composed of 97% magnesium, 2% aluminum, and 1% of rare earth metals (Ce, Pr, Nd), and WE43 is composed of >85% magnesium, <5% yttrium, <5% of zirconium, and <5% of rare earth metals.…”