Background
Yearly, doctors implant more than 800,000 stainless steel and cobalt-chromium cardiac stents to prop open arterial areas narrowed by hard and soft plaque deposits (stenosis). These stents become a permanent part of the arterial wall, which can lead to a variety of problems. The most commonly encountered problem is re-narrowing of the artery (restenosis), with 20% of stents undergoing restenosis within the first year. Drug-eluting stents (DES) have addressed this problem, but introduced other issues, such as an increased relative risk for late thrombosis (blood clots). Other problems include (1) difficulties with MRI imaging, (2) limitations on further intervention because of numerous permanent stents already in the artery (“full metal jacket” limitations), (3) inability to help infants and small children whose growing arteries need a stent that either grows with the artery or disappears, and (4) concerns about long-term biologic interactions between metal and/or polymers and arterial walls.

Invention Description
Mechanically strong, bioabsorbable stents could alleviate many if not all of the shortcomings mentioned above. Initial attempts at bioabsorbable stents have used magnesium, but concerns about dissolution rates and material release have limited their applicability. This invention addresses these issues by using a novel vapor deposition process. The process allows tailoring of the chemistry of the Mg alloy over a much broader range of compositions and maintains a solid solution alloy that allows better control of the corrosion/dissolution characteristics of the material compared to cast or wrought Mg alloy. The chemistry of these alloys can be varied, allowing for the production of equilibrium or non-equilibrium alloys. Such structuring could be used at the micro- or nano-scale for drug elution or for altering surface characteristics (hydrophilic or hydrophobic properties) of the stent without a requirement for the presence of polymers. Films created by this process can be used for a variety of bioabsorbable and biocompatible applications and for non-biological application as well.

File Number: 3248