Preparation of highly wettable coatings on Ti–6Al–4V ELI alloy for traumatological implants using micro-arc oxidation in an alkaline electrolyte (original) (raw)

Pulsed micro-arc oxidation (MAO) in a strongly alkaline electrolyte (pH > 13), consisting of Na 2 SiO 3 ⋅9H 2 O and NaOH, was used to form a thin porous oxide coating consisting of two layers differing in chemical and phase composition. The unique procedure, combining MAO and removal of the outer layer by blasting, enables to prepare a coating suitable for application in temporary traumatological implants. A bilayer formed in an alkaline electrolyte environment during the application of MAO enables the formation of a wear-resistant layer with silicon incorporated in the oxide phase. Following the removal of the outer rutile-containing porous layer, the required coating properties for traumatological applications were determined. The prepared surfaces were characterized by scanning electron microscopy, X-ray diffraction patterns, X-ray photoelectron spectroscopy, atomic force microscopy and contact angle measurements. Cytocompatibility was evaluated using human osteoblast-like Saos-2 cells. The newly-developed surface modifications of Ti-6Al-4V ELI alloy performed satisfactorily in all cellular tests in comparison with MAO-untreated alloy and standard tissue culture plastic. High cell viability was supported, but the modifications allowed only relatively slow cell proliferation, and showed only moderate osseointegration potential without significant support for matrix mineralization. Materials with these properties are promising for utilization in temporary traumatological implants. Titanium and titanium alloys are materials with an increasing share of applications in many fields, primarily in the aerospace industry, in healthcare, in the automotive industry, and now also in the offshore industry. Because of its favorable mechanical properties, Ti-6Al-4V ELI alloy is currently one of the most widely-used titanium alloys for medical applications. The applications are successfully realized despite the presence of aluminum and vanadium, which are potentially harmful alloying elements that might be released in the form of ions from the bulk material under specific tribocorrosion conditions 1,2. However, the presence of these alpha and beta stabilizing elements (Al and V, respectively) provides the alloy with great corrosion resistance and with suitable mechanical properties, such as moderate tensile and fatigue strength, formability and good creep resistance 3,4. The basic requirement for materials used in biomedical implants is that they should be biocompatible. This involves mutual interplay among a number of key material properties that define the best-possible contact with an internal environment within the human body. Not only the surface morphology and the physical properties of the material are important, but also the chemistry of the surface layer and the physiological environment to which the implants are to be exposed. By selecting a suitable modification method, it is possible to achieve a functional