Biocompatibility and bio-corrosion resistance of amorphous oxide thin films
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Biocompatibility and bio-corrosion resistance of amorphous oxide thin films P. N. Rojas1, S. E. Rodil1, S. Muhl1, G. Ramírez G.1, H Arzate2 1
Instituto de Investigaciones en Materiales, Universidad Nacional Autónoma de México, Circuito Exterior s/n, CU, México D.F. 04510, México 2 Laboratorio de Biología Celular y Molecular, Facultad de Odontología, Universidad Nacional Autónoma de México, CU, México D.F. 04510, México ABSTRACT The corrosion resistance of biocompatible materials in body fluids is one of the essential factors in the determination of the lifetime of medical implants. Therefore, it is of great relevance to understand the interface processes that occur when a surface is exposed to body fluids. To this end, amorphous titanium and niobium oxide films were deposited on medical grade stainless steel using a magnetron sputtering system. The biocompatibility of the films was evaluated by adhesion and viability/proliferation assays using human cells, showing non-toxic response. The electrochemical response of the films was evaluated by poteontiodynamic polarization and electrochemical impedance spectroscopy (EIS) as a function of time, up to 500 hrs, using three different simulated body fluids; the NaCl solution and Hartman (Ringer’s + Lactate) and Gey’s (Ringer’s + Phosphates + Glucose) solution. The results indicated that the chemical composition of the solution was very important since different electrochemical behavior was observed for each case. For example, NbOx showed a better resistance than the TiOx films in the Hartman’s solution but it failed when Gey’s solution was used. Meanwhile TiOx showed a well passivated response for both NaCl and Gey’s solution. INTRODUCTION Improving the long-term biocompatibility of metallic biomaterials has driven biomedical research towards more complex materials, such as alloys, composites or coated-metals 1, 2. The current trend is to use surface modification technologies to address a variety of new clinical demands. These demands include physico-chemical properties such as, wear-corrosion resistance 3, 4 or bio-functional properties, such as, osteoconductivity and oseoinductivity 3, 5-7, ie. bone growth promotion. Titanium and its alloys present high corrosion resistance and the best osseointegration and in consequence better long-term stability 8, 9. Nevertheless, titanium has been detected in the tissue around Ti implants, mainly due to the repetitive destruction of the passive film by wear and fretting 10, 11. This release of metal ions can cause adverse effects, toxicity, carcinogenicity and metal allergy 11, 12 . Similarly, the corrosion resistance of the stainless steel passive film is relatively high but it is highly susceptible to pitting corrosion, thus limiting the use of stainless steel to short-term implants 13, 14. The deposition of a biocompatible-biofunctional and corrosion resistance thin films on a medical grade metallic substrate might lead to the development of the ideal biomaterial and coating of metallic biomaterials using a large variety of mate
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