Direct Writing of Polymeric Coatings on Magnesium Alloy for Tracheal Stent Applications
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This paper investigates the direct-write inkjet method for depositing multi-layer coatings of biodegradable polymers on magnesium alloy surface. Immersion studies were conducted on Poly(lactic-co-glycolic) acid (PLGA), polycaprolactone (PCL), and poly-ester urethane urea (PEUU) coatings to determine the corrosion behavior of different samples based on their varying degradation properties. Using the inductively coupled plasma spectroscopy, a reduction in magnesium ion concentration was observed from the polymer-coated samples indicative of the lower corrosion rates as compared to the uncoated Mg substrate. Findings also showed correlation between the release of the magnesium ions and the health of fully differentiated normal human bronchial epithelial (NHBE) cells via evaluation of key biomarkers of inflammation and toxicity, cyclooxygenase-2 (COX-2) and lactate dehydrogenase (LDH), respectively. The induction of COX-2 gene expression was proportional to the increase in magnesium exposure. In addition, the release of higher magnesium content from uncoated and PCL polymer coated samples resulted in lower LDH activity based on the favorable response of the NHBE cells. PEUU and PLGA polymer coatings provided good barrier layer corrosion protection. This research evaluates candidate polymer coatings as a source for therapeutic agents and barrier layer to control the corrosion of magnesium alloys for tracheal applications.
KeywordsBiomedical Corrosion control Inkjet printing Lactate dehydrogenase release assay Polymerase chain reaction
The authors would like to thank the NSF Engineering Research Center for Revolutionizing Metallic Biomaterials (NSF–EEC Award #0812348) and NSF CAREER Award #0846562 for support towards this research. We would also like to express our gratitude to Dr. Yi Hong (Wagner Laboratories, McGowan Institute for Regenerative Medicine, Univ. of Pittsburgh) for providing proprietarily formulated PEUU polymer. Dr. P. N. Kumta would like to acknowledge the Edward R. Weidlein Chair Professorship and the Center for Complex Engineered Multifunctional Materials (CCEMM) at the Univ. of Pittsburgh for providing the equipment and facilities needed for ICP analysis.
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