Contents lists available at ScienceDirect Surface & Coatings Technology journal homepage: www.elsevier.com/locate/surfcoat Superhydrophilic nanostructured surfaces of beta Tie29Nb alloy for cardiovascular stent applications Jithin Vishnu a , Mariana Calin b , Stefan Pilz b , Annett Gebert b , Beata Kaczmarek c , Marta Michalska-Sionkowska d , Volker Hoffmann b , Geetha Manivasagam a, ⁎ a Centre for Biomaterials Cellular and Molecular Theranostics, Vellore Institute of Technology, Vellore, India b Institute for Complex Materials, Leibniz IFW Dresden, Helmholtzstr-20, 01069 Dresden, Germany c Department of Chemistry of Biomaterials and Cosmetics, Faculty of Chemistry, Nicolaus Copernicus University in Toruń, Toruń, Poland d Department of Environmental Microbiology and Biotechnology, Faculty of Biology and Veterinary Science, Nicolaus Copernicus University in Toruń, Torun, Poland ARTICLE INFO Keywords: Beta titanium alloy Ni-free Ti-based cardiovascular stents Surface modification Nanograss Superhydrophilic surface Hemocompatibility ABSTRACT Nanostructured coatings on cardiovascular stent surfaces can significantly alter the blood cell response and can effectively tailor the anti-thrombotic potential of the surfaces. The present work investigates the specific impact of physico-chemical characteristics of a hydrothermally treated beta-type Tie29Nb (at.%) alloy. Surface tailored nanostructured titania surfaces on TiNb alloy and the ensuing blood compatibility have been analyzed. Nanograss-like structures were successfully fabricated on TiNb alloy surfaces via a facile hydrothermal tech- nique. The developed structures exhibited nanotopographies and composed predominantly of anatase titania. Wettability studies revealed the superhydrophilic property of the developed nanograss structures and these structures exhibited reduced hemolysis rates and meagre platelet adhesion and activation. The underlying mechanism of these characteristics is explained in terms of morphology, roughness and chemical composition. In conclusion it is demonstrated that the developed superhydrophilic surface coating can provide new opportunity for blood contacting implant applications. 1. Introduction Despite the advancements in global healthcare field, cardiovascular diseases still persist as the leading cause of mortality globally (17.8 million deaths in 2017), posing a major hurdle to sustainable human development [1]. One of the most perilous cardiovascular diseases is the coronary artery disease (CAD) characterized by the deposition of plaque material inside human arterial lumen which clogs arterial blood flow. In order to treat these intra-arterial blood clots, coronary stenting is a potential clinical technique. In this technique, the arterial lumen is propped open with the aid of an expandable mesh tube thereby en- suring immediate as well as long-term patency rates (likelihood of a vessel to be remained open). Among the stents, self-expandable me- tallic-type is a widely used class of stent which utilizes the superelastic property of the stent's metallic material to assist in expansion of the stent at the region of blockage [2]. Nitinol (equiatomic nickel‑titanium alloy) is unequivocally the most prevalent material being used for self-expandable metallic stents owing to its unparallel superior superelasticity effect (transformation strains up to 7%) [3,4]. Even though a protective native titanium oxide (TiO 2 ) layer covers the nitinol surface, tiny deposits of nickel (Ni) compounds can diffuse through the surface and will be systemically transported by the lymphatic system [5]. Ni rich regions composed of Ti 4 Ni 2 O x , Ni 4 Ti 3 and Ni 3 Ti can act as potential corrosion initiation sites leading to this Ni ion leaching particularly in high chloride content of blood [6]. Con- sequent adverse events can rise from leached Ni ions eliciting in- flammatory cell response resulting in neointimal hyperplasia, nickel hypersensitivity, nephrotoxicity and carcinogenicity [7–9]. These con- troversial concerns led to growing interest in alternative Ni-free Ti based (particularly beta TiNb) alloys exhibiting superelastic behavior based on the martensitic transformation from body centred cubic to orthorhombic martensite depending on alloy composition (transfor- mation strains up to 4.2%) [10–12]. Apart from superelasticity, TiNb alloys are potential materials for stent materials as it contains niobium which is cytocompatible [13,14] as well as hypoallergenic [15,16]. In addition to the required mechanical properties, another im- portant factor to be addressed is the stent material surface which should possess enhanced hemocompatibility to prevent the occurrence of ad- verse thrombotic events leading to thrombosis, in-stent restenosis and neoatherosclerosis. One of the widely used therapeutic methods to https://doi.org/10.1016/j.surfcoat.2020.125965 Received 25 March 2020; Received in revised form 21 May 2020; Accepted 24 May 2020 ⁎ Corresponding author. E-mail address: geethamanivasagam@vit.ac.in (G. Manivasagam). Surface & Coatings Technology 396 (2020) 125965 Available online 29 May 2020 0257-8972/ © 2020 Elsevier B.V. All rights reserved. T