Materials Frontier No.131
Title: Biodegradable magnesium alloy stents: modeling and experimental studies
Speaker: Prof. Francesco Migliavacca,
Laboratory of Biological Structure Mechanics,Chemistry,
Materials and Chemical Engineering 'Giulio Natta' Dept, Politecnico di Milano,Italy
Inviter: Prof Guangyin YUAN
Prof. Francesco Migliavacca obtained a MSc in Mechanical Engineering and a PhD in Bioengineering both from Politecnico di Milano. In 2000 he worked as a Research Assistant at the Cardiothoracic Unit ofGreatOrmondStreetHospitalfor Children inLondonin 1994 and 1997-99. In 2000 and 2001 he was consultant and Research Scientist at the Pediatric Cardiac Surgery Department of theUniversityofMichigan,Ann Arbor,MI,USA. At present he is Full Professor of Bioengineering in the Department of Chemistry, Materials and Chemical Engineering ‘Giulio Natta’ of Politecnico di Milano. Since September 2007 he is the Director of the Laboratory of Biological Structure Mechanics (LaBS) of the Politecnico di Milano. His major research activities have included the fluid dynamic optimization of pediatric cardiac surgery procedures, fluid dynamics in the living systems as well as structural analysis and material behavior of biomedical devices, in particular intravascular stents. He is involved in funded researches from the European Commission, the Foundation Leducq and public and private Italian National programs. He received the medal 'Le Scienze 2001' in Engineering and was awarded the European Society of Biomechanics Perren Award in 2004. He is Associate Editor of the peer-reviewed journals ‘Cardiovascular Engineering and Technology’ and ‘Frontiers in Pediatric Cardiology’.
Biodegradable magnesium alloy stents (MAS) could improve long-term clinical results of commercial bare metal or drug-eluting stents. However, MAS have shown limited mechanical support for diseased vessels with fast degradation. This talk sums a series of modeling and experimental studies of MAS carried out at Politecnico di Milano to improve MAS' scaffolding and enforce anti-corrosion ability. First, shape optimization was carried out to obtain a new MAS design with a good balance of expansion strain and stent mass. An elongation experiment verified the optimized design improved expansion deformation over the non-optimized design. Second, a degradable material model of magnesium alloy was applied to three different MAS designs including the optimized one above. The degradation process of the three designs and their interactions with vessel model were simulated for comparison. The optimized design showed much better scaffolding properties during corrosion than the other two, including a design with more mass. After that, a corrosion experiment was carried out to compare the anti-corrosion ability between the optimized design and the design with more mass. The laser-cut stent samples of the optimized design showed expected better corrosion resistance than the samples of the other design when immersed in D-Hanks’ solution after expansion. Finally, peeling experiment of polymer coating on magnesium alloy samples were done to obtain the material parameters of the peeling process. Then a peeling model was built using the parameters to predict the possibility of polymer coating peeling from coated MAS of the optimized design during stent expansion. All the work together has basically structured a framework to design and test novel MAS for the future clinical demanding.