Design of polymer coatings on Nitinol by surface-initiated polymerization

: Towards cardiovascular applications

Résumé

Over the last decade Nitinol (NiTi) has become very appealing owing to its attractive properties (good impact and heat resistance, high fatigue strength, low density, ...). Nowadays, it is commonly used as a support material for the treatment of cardiovascular disease where it is used as a stent. However, its im-plementation in the biomedical fields is still hampered by nickel inclusions, making this alloy sensitive to pitting corrosion and leading therefore to the re-lease of carcinogenic Ni2+ ions.

The present thesis is devoted to the improvement of NiTi properties. The main objectives are to increase the material corrosion resistance, its biocompati-bility, as well as its hydrophilicity to prevent the adhesion of fat and proteins on its surface. In this context, three steps are considered and investigated: (a) the hydrothermal reinforcement of Nitinol native oxide layer; (b) the elaboration of an organic monolayers containing polymerization moieties; and (c) the subse-quent growth of a biocompatible layer. More specifically, the electro-assisted elaboration of self-assembled monolayers (SAM) is proven to allow fast prepara-tion of protective coatings in mild conditions while preventing degradation of sensitive molecules such as the ATRP initiating sites. However, the steric hin-drance of ATRP initiating sites interferes with the formation of ordered and compact SAMs, leading to a bad reinforcement of the metal surface corrosion resistance. To face this issue, the elaboration of alternative initiating layers, i.e. mixed- or bisphosphonic-made monolayers, are investigated. Finally, the behav-iour of modified Nitinol plates in human blood plasma simulated fluid, and its ability to grow endothelial cells are investigated.

la date de réponse	7 déc. 2018
langue originale	Anglais
L'institution diplômante	Universite de Namur
Sponsors	Université de Namur & Université de Mons
Superviseur	Zineb Mekhalif (Promoteur), Stephane Lucas (Président), Laetitia Mespouille (Copromoteur), Philippe H. Dubois (Jury) & Jean-François Vanhumbeeck (Jury)