Date Published: October 10, 2018
Publisher: Public Library of Science
Author(s): Lumei Liu, Sang-Ho Ye, Xinzhu Gu, Teal Russell, Zhigang Xu, Jagannathan Sankar, William R. Wagner, Young-Choon Lee, Yeoheung Yun, Mária A. Deli.
Polymeric coatings can provide temporary stability to bioresorbable metallic stents at the initial stage of deployment by alleviating rapid degradation and providing better interaction with surrounding vasculature. To understand this interfacing biocompatibility, this study explored the endothelial-cytocompatibility of polymer-coated magnesium (Mg) alloys under static and dynamic conditions compared to that of non-coated Mg alloy surfaces. Poly (carbonate urethane) urea (PCUU) and poly (lactic-co-glycolic acid) (PLGA) were coated on Mg alloys (WE43, AZ31, ZWEKL, ZWEKC) and 316L stainless steel (316L SS, control sample), which were embedded into a microfluidic device to simulate a vascular environment with dynamic flow. The results from attachment and viability tests showed that more cells were attached on the polymer-coated Mg alloys than on non-coated Mg alloys in both static and dynamic conditions. In particular, the attachment and viability on PCUU-coated surfaces were significantly higher than that of PLGA-coated surfaces of WE43 and ZWEKC in both static and dynamic conditions, and of AZ31 in dynamic conditions (P<0.05). The elementary distribution map showed that there were relatively higher Carbon weight percentages and lower Mg weight percentages on PCUU-coated alloys than PLGA-coated alloys. Various levels of pittings were observed underneath the polymer coatings, and the pittings were more severe on the surface of Mg alloys that corroded rapidly. Polymer coatings are recommended to be applied on Mg alloys with relatively low corrosion rates, or after pre-stabilizing the substrate. PCUU-coating has more selective potential to enhance the biocompatibility and mitigate the endothelium damage of Mg alloy stenting.
Magnesium (Mg)-based alloys are bioresorbable scaffold materials that demonstrate enhanced properties of biodegradability and biocompatibility, and thus are being investigated for medical applications, such as atherosclerosis treatment [1, 2]. Magnesium-based alloys have been studied in both in vitro and animal models [3–5], and Mg-based metal scaffolds have been tested in clinical trials for cardiovascular atherosclerosis . However, there are few studies on magnesium alloys for other atherosclerotic diseases, such as intracranial atherosclerotic disease (ICAD), which has been claimed to be the most common cause of stroke worldwide . Current treatments of ICAD are brain stents, medications, and surgery . Brain stents made of permanent metallic materials have some risks upon implantation: artery puncture, stent movement, damage to the lining of the vessel causing an artery dissection, bleeding into the brain, and stroke from artery blockage . Based on the studies of Mg alloys for cardiovascular application, Mg alloys show promise in addressing these risks. Magnesium-based alloys are potentially biocompatible and provide high tensile strength (~542 MPa ) with lightweight properties, thus presenting new opportunities for cerebral stent application.
The test of endothelial cell attachment indicates that both PCUU and PLGA coatings on Mg alloys are capable of improving initial endothelial cell adhesion. PCUU coating has a greater ability to improve endothelial cell attachment on more alloy surfaces compared to PLGA coating. Pittings are more severe on the surface of Mg alloys that corrode rapidly, thus coatings are strongly recommended be applied on Mg alloys with relatively low corrosion rates, or on pre-stabilized Mg substrates.