Hemocompatibility Improvement of Chromium-Bearing Bare-Metal Stent Platform After Magnetoelectropolishing

Abstract

Research was undertaken to determine the influence of the increased content of chromium in the outermost passive layer of magneto-electrochemically refined Co-Cr alloy L-605 surface on its hemocompatibility. The chemistry, roughness, surface energy, and wettability of conventionally electropolished (EP) and magnetoelectropolished (MEP) samples were studied with x-ray photoelectron spectroscopy (XPS), open circuit potential, atomic force microscopy, and contact angle meter. In vitro hemocompatibility of tested material surfaces was assessed using two important indicators of vascular responses to biomaterial, namely endothelialization and platelets adhesion. The endothelialization was assessed by seeding and incubating samples with human umbilical vein endothelial cells (HUVEC) for 3 days before counting and observing them under a fluorescent microscope. The platelet (rich plasma blood) adhesion and activation test on EP and MEP L-605 alloy surfaces was assessed using a laser scanning confocal microscope. The XPS analysis of MEP samples showed significant enrichment of the passive layer with Cr and O when compared with the EP one. The amount of other elements in the passive layer did not show a significant difference between EP and MEP treatments. The adhesion of HUVEC cells shows remarkable affinity to surfaces enriched in Cr (MEP) with almost 100% confluency. In addition, the number of platelets that adhered to standard EP surfaces was higher compared to the MEP surface. The present study shows that the chromium-enriched surface of cobalt-chromium alloy L-605 by the magnetoelectropolishing process tremendously improves surface hemocompatibility with regard to stent functionality by enhanced endothelialization and lower platelet adhesion and should be taken under consideration as an alternative surface of biodegradable polymer drug-eluting stents, polymer-free drug-eluting stents as well as bare-metal stents.