Novel nanostructured biomaterials: implications for coronary stent thrombosis

Varvara Karagkiozaki,^1,2 Panagiotis G Karagiannidis,¹ Nikolaos Kalfagiannis,¹ Paraskevi Kavatzikidou,¹ Panagiotis Patsalas,³ Despoina Georgiou,¹ Stergios Logothetidis<sup>1

1</sup>Lab for Thin Films – Nanosystems and Nanometrology (LTFN), Physics Department, Aristotle University of Thessaloniki, Thessaloniki, ²AHEPA Hospital, Aristotle University of Thessaloniki, Thessaloniki, ³Department of Materials Science and Engineering, University of Ioannina, Ioannina, Epirus, Greece

Background: Nanomedicine has the potential to revolutionize medicine and help clinicians to treat cardiovascular disease through the improvement of stents. Advanced nanomaterials and tools for monitoring cell–material interactions will aid in inhibiting stent thrombosis. Although titanium boron nitride (TiBN), titanium diboride, and carbon nanotube (CNT) thin films are emerging materials in the biomaterial field, the effect of their surface properties on platelet adhesion is relatively unexplored.
Objective and methods: In this study, novel nanomaterials made of amorphous carbon, CNTs, titanium diboride, and TiBN were grown by vacuum deposition techniques to assess their role as potential stent coatings. Platelet response towards the nanostructured surfaces of the samples was analyzed in line with their physicochemical properties. As the stent skeleton is formed mainly of stainless steel, this material was used as reference material. Platelet adhesion studies were carried out by atomic force microscopy and scanning electron microscopy observations. A cell viability study was performed to assess the cytocompatibility of all thin film groups for 24 hours with a standard immortalized cell line.
Results: The nanotopographic features of material surface, stoichiometry, and wetting properties were found to be significant factors in dictating platelet behavior and cell viability. The TiBN films with higher nitrogen contents were less thrombogenic compared with the biased carbon films and control. The carbon hybridization in carbon films and hydrophilicity, which were strongly dependent on the deposition process and its parameters, affected the thrombogenicity potential. The hydrophobic CNT materials with high nanoroughness exhibited less hemocompatibility in comparison with the other classes of materials. All the thin film groups exhibited good cytocompatibility, with the surface roughness and surface free energy influencing the viability of cells.

Keywords: platelets, cell viability, titanium boron nitride, atomic force microscopy, carbon nanotubes