Browsing by Author "Akman, Adnan"

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    Designing Gallium-Containing Hydroxyapatite Coatings on Low Modulus Beta Ti-45Nb Alloy
    (Basel : MDPI, 2023) Vishnu, Jithin; Voss, Andrea; Hoffmann, Volker; Alberta, Ludovico Andrea; Akman, Adnan; Shankar, Balakrishnan; Gebert, Annett; Calin, Mariana
    Low-modulus β-type Ti-45Nb alloy is a promising implant material due to its good mechanical biocompatibility, non-toxicity, and outstanding corrosion resistance. Its excellent chemical stability brings new challenges to chemical surface modification treatments, which are indispensable for both osteogenesis and antibacterial performance. Coatings containing metal ions as anti-microbial agents can be an effective way to reduce implant-associated infections caused by bacterial biofilm. Gallium ion (Ga3+) has the potential to reduce bacterial viability and biofilm formation on implant surfaces. In this study, a novel two-step process has been proposed for Ga3+ incorporation in hydroxyapatite (HAP) to develop bioactive and antibacterial surfaces on Ti-45Nb alloy. For the generation of bioactive surface states, HAP electrodeposition was conducted, followed by wet chemical immersion treatments in gallium nitrate (1 mM). Different buffers such as phosphate, sodium bicarbonate, ammonium acetate, and citrate were added to the solution to maintain a pH value in the range of 6.5–6.9. Coating morphology and HAP phases were retained after treatment with gallium nitrate, and Ga3+ ion presence on the surface up to 1 wt.% was confirmed. Combining Ga and HAP shows great promise to enable the local delivery of Ga3+ ions and consequent antibacterial protection during bone regeneration, without using growth factors or antibiotics.
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    Effect of minor gallium addition on corrosion, passivity, and antibacterial behaviour of novel β-type Ti–Nb alloys
    (Sao Paulo : ABM, 2023) Akman, Adnan; Alberta, Ludovico Andrea; Giraldo-Osorno, Paula Milena; Turner, Adam Benedict; Hantusch, Martin; Palmquist, Anders; Trobos, Margarita; Calin, Mariana; Gebert, Annett
    Metastable Ti–Nb alloys are promising bone-implant materials due to improved mechanical biofunctionality and biocompatibility. To overcome increasing bacterial infection risk, alloying with antibacterial elements is a promising strategy. This study investigates the effect of minor gallium (Ga) additions (4, 8 wt% Ga) to as-cast and solution-treated β-type Ti–45Nb-based alloy (96(Ti–45Nb)-4Ga, 92(Ti–45Nb)-8Ga (wt.%)) on corrosion and passive film properties, as well as cytocompatibility and antibacterial activity. The electrochemical properties were evaluated by potentiodynamic polarization, electrochemical impedance spectroscopy (EIS), and Mott-Schottky analyses in phosphate-buffered saline (PBS). X-ray photoelectron spectroscopy (XPS) was performed to analyze the chemical composition of passive films. Early adhesion and viability of macrophages and Staphylococcus aureus were assessed by nucleocounting and colony-forming unit counting, respectively. The results showed that high corrosion resistance and passive film properties of Ti–45Nb are retained and even slightly improved with Ga. EIS results revealed that Ga addition improves the passive film resistance. XPS measurements of 92(Ti–45Nb)-8Ga show that the passive film contains Ti-, Nb- and Ga-based oxides, implying the formation of mixed (Ti–Nb-Ga) oxides. In addition, marginal Ga ion release rate was detected under free corrosion conditions. Therefore, it can be assumed that Ga species may contribute to passive film formation on Ga-containing alloys. The 92(Ti–45Nb)-8Ga elicited an antibacterial effect against S. aureus compared to cp-Ti at 4 h. Moreover, Ga-containing alloys showed good cytocompatibility with THP-1 macrophages at 24 h. In conclusion, it was demonstrated that Ga additions to Ti–45Nb are beneficial to corrosion resistance and showed promising initial host and bacterial interactions.
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    Tribocorrosion behaviour of additively manufactured β-type Ti–Nb alloy for implant applications
    (Rio de Janeiro : Elsevier, 2024) Akman, Adnan; Douest, Yohan; Alberta, Ludovico Andrea; Perrin, Kevin; Trunfio Sfarghiu, Ana-Maria; Courtois, Nicolas; Ter-Ovanessian, Benoit; Pilz, Stefan; Zimmermann, Martina; Calin, Mariana; Gebert, Annett
    β-type Ti–Nb alloys are promising materials for load-bearing implant applications with improved mechanical biofunctionality and biocompatibility. In this work, the electrochemical and tribo-electrochemical behaviour of laser powder bed fusion (LPBF) produced β-type Ti–42Nb alloy processed via Gaussian and top hat laser was investigated and compared with commercial grade β-type Ti–45Nb and α+β-type Ti–6Al–4V ELI. Electrochemical impedance spectroscopy (EIS) and potentiodynamic polarization experiments were performed in phosphate-buffered saline (PBS) for corrosion behaviour. Tribocorrosion behaviour was studied under open circuit potential (OCP) conditions in PBS by using a reciprocating pin-on-disk tribometer. The passivation nature of the LPBF alloys is more decisive than the microstructural particularities for electrochemical behaviour. The overall corrosion response is similar due to the protective nature of the passive films formed on Ti alloys. Ti–6Al–4V ELI exhibits the best corrosion performance among all tested alloys with lower corrosion and passivation current density values. However, LPBF-produced alloys exhibit less reactive surfaces with better passive film properties compared to Ti–45Nb. In addition, EIS results revealed that passive film resistance values are higher for LPBF-produced alloys than conventionally produced Ti–45Nb. LPBF-produced alloys exhibit better tribo-electrochemical behaviour compared to Ti–45Nb. The differences in volume loss are mainly attributed to the microhardness of the alloys and the volume loss is dominated by mechanical wear. The alloys produced with LPBF show promising corrosion and tribocorrosion performance to be a potential candidate for load-bearing implant applications.