Bioabsorbable Magnesium Alloy Stents

Background

Metallic stents made from magnesium alloys have the benefit of being bioabsorbable but the risk of fracture during manufacturing has presented a technological barrier. Strathclyde has developed a process which improves the tensile strength of this naturally brittle material to improve its performance during the metal forming process and surgical placement.

The world stent market has an estimated value of US$6.4 billion. Stenting is performed in approximately 60 percent of balloon angioplasty cases. Coronary stents are now the most commonly implanted medical device, with more than one million being implanted in the United States alone.

The current stent technology is based on the use of a permanent stent made from corrosion-resistant metals. However, once the vessel has healed, the scaffolding function of the stent is no longer needed, and the presence of a permanent metallic prosthesis poses important disadvantages. The alternative is bioabsorbable stents made of polymers or metals. One of the metal candidates is magnesium alloys, which unfortunately have very low ductility which makes their forming into minitubes (precursors to mesh-like tubular scaffolds) difficult. Additionally, when the mesh is expanded by a balloon, it should be ductile enough to avoid fracture of the mesh struts. Our technology makes the naturally brittle magnesium alloy much more ductile.

Technology

Our patented process for improving magnesium properties is based on grain refinement achieved by so-called severe plastic deformation of the coarse grained material. The process, known as Incremental Equal Channel Angular Pressing (I-ECAP), has been proved on a laboratory scale but since it can deal with very long (theoretically infinite) billets it is useful for industrial implementation. Different post-processing options enable further improvement of the mechanical properties of the materials.

Key benefits

  • improved ductility of brittle metallic materials such as magnesium alloys
  • improved yield strength
  • high material utilisation due to long billets
  • various cross sections, eg bars, plates and sheets
  • ease of forming into products, such as stent minitubes
  • adequate room temperature ductility to avoid fracture during ballooning
  • uniform properties in the thickness direction of stent strut because of very fine grains, about one micron

Markets & applications

  • stent manufacturers
  • all types of stents

Licensing & development

This technology is protected by granted European (EP1861211) and US patents (US8,631,673). We are seeking commercial partners for scaling up the process and/or supporting further research into testing of different metallic materials useful for bioabsorbable stents. We also welcome approaches from companies interested in licensing our patents. In the first instance please contact RKES for further information.