Exploratory research to suppress intimal hyperplasia by controlling zinc implant biodegradation

Michigan Technological University, Houghton MI

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Abstract

Summary A new generation of bioabsorbable metal stents is currently being developed to be fully absorbed after completing their task as vascular scaffolding. A breakthrough in the field was made in 2012 in our research team with the introduction of zinc (Zn) and its alloys. A big surprise of our earlier exploratory work has motivated us to explore the effect of zinc degradation on the formation of intimal hyperplasia. We discovered a gradient of smooth muscle cells (SMCs) within the stable neointima surrounding the zinc implants out to 6 months. A thin band of SMCs was present along the outer perimeter of the neointima, with no SMCs closer to the implant surface. The cell gradient and stability of the SMC layer strongly suggests a mechanism of active cell suppression, a possibility never explored in the scientific literature for metallic materials. Following these findings, we propose to explore the effect of metal biodegradation rate on formation of neointimal hyperplasia. Biodegradation rate will be controlled through a refinement of zinc material microstructure (through varying processing and thermal treatments of the same material) and surface finish (varying conditions of electropolishing and anodization). Generating an improved suppression of SMCs by regulating the flux of biocorrosion products is, in our opinion, a new direction for rational metallurgical engineering of biodegradable Zn implants. This exploratory direction could lay the groundwork to pioneer a new integrative field of materials science and biomedical engineering.