Advanced Materials & Processing

Biography

Biography: Metka bencina

Abstract

Despite intensive research and applications of different techniques to improve surface properties of vascular stents, currently available metal stents and their coatings (DES - drug eluting stents) still lack of desired surface biocompatibility, mostly due to mechanical injuries, inflammation, as well as proliferation and migration of smooth muscle cells, often with progression to restenosis [1]. Besides, the durability and stability of DES is still problematic and has been connected with high risk of thrombosis [2, 3]. Biomimetic nano-sized materials, with their crystal structure, surface morphology and chemical properties are one of critical features for their potential use in vascular stent applications, which should support adhesion, proliferation and differentiation of endothelial cells and prevent abnormal growth of smooth muscle cells. For example, it was shown that titanium dioxide (TiO₂) nanotubes (NTs) topography is essential parameter in optimizing endothelial cell and smooth muscle cell responses to vascular implants [4]. The purpose of this study is to investigate surface properties and crystal structure of TiO₂ NTs. Since the oxygen plasma treatment plays significant role in surface treatment of biomedical devices due to surface cleaning and sterilization, its effect on the mechanical stability and surface chemical properties was evaluated. Vertically-aligned arrays of TiO₂ NTs were synthesized on Ti metallic substrates with electrochemical anodization [5]. The crystal structure was investigated with X-ray Diffraction Spectroscopy, while morphology and surface properties were analyzed with Scanning Electron Microscopy coupled with Energy Dispersive X-ray Analysis, X-ray Photoelectron Spectroscopy and Water Contact Angle analysis. Our results indicate that oxygen plasma treatment of TiO₂ NTs surfaces induces the formation of oxide layer on the surface of TiO₂ NT, which could result in enhanced biocompatibility. Moreover, plasma treatment removes undesired electrolyte residues on TiO₂ NTs surface and highly improves its wettability. We showed that plasma treated TiO₂ NTs possess long-term hydrophilicity and influence on crystallization of amorphous TiO₂ NTs to anatase and/or rutile crystal phase, which could be the reason for improved wettability. The optimized conditions (power, frequency and time) of oxygen plasma treatment on the mechanical stability of TiO₂ NTs are also presented. Oxygen plasma treatment can greatly improve the surface characteristics of biomimetic materials and enhance their biocompatibility. Restenosis and thrombosis still remain a serious concern and should be given a great deal of attention in order to produce improved tissue-material response.

Recent Publications :

1. Hoffmann R, Mintz GS, Dussaillant GR, Popma JJ, Pichard AD, Satler LF, Kent KM, Griffin J, Leon MB (1996) Patterns and mechanisms of in-stent restenosis. A serial intravascular ultrasound study. Circulation, 94(6): p. 1247-1254.
2. De la Torre-Hernández JM, Alfonso F, Hernández F, Elizaga J, Sanmartin M, Pinar E, ... & Hernández JM (2008) Drug-eluting stent thrombosis. Journal of the American College of Cardiology, 51(10), 986.
3. Doyle B, Rihal CS, O’Sullivan CJ, Lennon RJ, Wiste HJ, Bell M, ... & Holmes DR (2007) Outcomes of stent thrombosis and restenosis during extended follow-up of patients treated with bare-metal coronary stents. Circulation, 116(21), 2391-2398.
4. Lu, J., Rao, M. P., MacDonald, N. C., Khang, D., & Webster, T. J. (2008). Improved endothelial cell adhesion and proliferation on patterned titanium surfaces with rationally designed, micrometer to nanometer features. Acta biomaterialia, 4(1), 192-201.
5. Kulkarni M, Mrak-Poljsak K, Flasker A, Mazare A, Schmuki P, Kos A, ... & Iglic A (2015) Fabrication of TiO₂ nanotubes for bioaplications. Materiali in tehnologije, 49(4), 635-637