Design, development and characterisation of novel polymer and ceramic based coating technologies to control the degradation rates of magnesium alloys for stent applications

Abstract

Cardiovascular diseases are the leading cause of death globally, according to the World Health Organisation, and represent a significant global disease burden. Permanent drug eluting stents remain the current gold standard for treatment of coronary artery disease. However, their permanent structure hinders vessel remodelling and there is a risk of late-stage thrombosis. To overcome the challenges which these permanent stents pose, research has looked to bioresorbable materials as an alternative approach.
While research investigating Magnesium (Mg) based cardiovascular stents is at a less advanced stage compared to their polymer counterparts, clinical studies such as the BIOSOLVE trials (Biotronik GmbH & Co. KG, Berlin, Germany) have shown promising results. However, the greatest challenge to the development of an Mg based stent has been the control of rapid degradation rates.

Coating technologies and surface treatments to control degradation rates need to achieve appropriate corrosion protection without compromising on overall scaffold thickness or causing deleterious changes to the mechanical properties of the Mg backbone, which may lead to early failure due to embrittlement of the scaffold. A key challenge for the development of suitable coatings to control Mg degradation rates is the complex geometry of a coronary stent, along with the functional requirements of a polymer coating for drug elution. The aggressive Mg corrosion reaction can result in poor polymer interfacial adhesion, and impaired drug release kinetics.

As such, a combined ceramic and polymer dual layered coating approach was identified as a potential method for controlling Mg degradation, furthermore this thesis aimed to examine the coatings performance with respect to three key areas: the degradation profile, the adhesive interface between polymer and ceramic, and the mechanical properties of the bulk Mg and coating system before, during and after degradation.

Thesis is embargoed until 31 December 2025.

Date of Award	Dec 2024
Original language	English
Awarding Institution	Queen's University Belfast
Sponsors	Horizon Europe: Marie Skłodowska-Curie Actions
Supervisor	Alex Lennon (Supervisor) & Gary Menary (Supervisor)