Drug-eluting stents (DES) have been widely applied for saving the life of patients with coronary artery diseases (CADs). However, conventional polymers such as polylactic acid (PLA) and poly (lactic-co-glycolic acid) (PLGA), which are widely applied for drug-eluting stents studies, have serious bulk erosion problems, like high local acidity and poor mechanical properties. Instead, we chose surface erosion polymer poly (1, 3-trimethylene carbonate) (PTMC) as a drug carrier in this study. Here, we fabricated and characterized a novel durable-polymer drug-eluting 316 L stainless steel (SS) stent, in which the inner surface was coated with a Ti–O film using the magnetron sputtering method to promote the growth of endothelial cells (ECs). On the outer layer of the stent, first, a Ti–O film was deposited and, then, on top of it a rapamycin-loaded PTMC coat was deposited using the ultrasonic atomization spray method. This dual coating inhibited the migration and expansion of smooth muscle cells (SMCs). The drug coating also inhibited the adhesion/activation of platelets. In tests on dogs, it was found the novel stent promoted re-endothelialization and reduced restenosis, in contrast to the plain SS stent. Thus, the novel stent may have promise for use in treating patients with CAD.
The tool steel AISI H13 is characterized by a high wear resistance and a good thermal shock resistance. H13 is mainly employed in applications such as tools for pressure die casting and forging. Processing of H13 by additive manufacturing techniques, such as selective laser melting (SLM), opens up new design possibilities with respect to e. g. internal cooling channels, in order to improve the tool performance during operation. However, due to high surface roughness and insufficient geometric accuracy imposed by SLM, additional cutting or forming processes are often required leading to an alteration of the surface and subsurface properties of the part. The presented work reveals the effect of SLM processing and subsequent face milling and/or deep rolling operations on the development of surface and subsurface properties and highlights adequate process windows.
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