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Titanium (Ti) is a popular biomaterial for orthopedic implant applications due to its superior mechanical properties such as corrosion resistance and low modulus of elasticity. However, around 10% of these implants fail annually due to bacterial infection and poor osseointegration, resulting in severe pain and suffering for the patients. To improve their performance, nanoscale surface modification approaches and doping of trace elements on the surfaces can be utilized which may help in improving cell adhesion for better osseointegration while reducing bacterial infection. In this work, at first, titania (TiO2) nanotube arrays (NT) were fabricated on commercially available pure Ti surfaces via anodization. Then zinc (Zn) doping was conducted following two distinct methods: hydrothermal and alkaline heat treatment. Scanning electron microscopic (SEM) images of the prepared surfaces revealed unique surface morphologies, while energy dispersive X-ray spectroscopy (EDS) revealed Zn distribution on the surfaces. Contact angle measurements indicated that NT surfaces were superhydrophilic. X-ray photoelectron spectroscopy (XPS) provided the relative amount of Zn on the surfaces and indicated that hydrothermally treated surfaces had more Zn compared to the alkaline heat-treated surfaces. X-ray crystallography (XRD) and nanoindentation techniques provided the crystal structure and mechanical properties of the surfaces. While testing with adipose-derived stem cells (ADSC), the surfaces showed no apparent cytotoxicity to the cells. Finally, bacteria adhesion and morphology were evaluated on the surfaces after 6 h and 24 h of incubation. From the results, it was confirmed that NT surfaces doped with Zn drastically reduced bacteria adhesion compared to the Ti control. Zn-doped NT surfaces thus offer a potential platform for orthopedic implant application. [ABSTRACT FROM AUTHOR]

Hydroxyapatite (HA) is a bioactive calcium phosphate capable of enhancing the implant/bone connection improving osteoconductivity and osseointegration process. However, the HA presents mechanical properties limiting its application. A good way to resolve this limitation is to combine the excellent biological properties of HA with materials with suitable mechanical behavior, like Ti-25Nb-25Ta alloy. The Ti-25Nb-25Ta alloy is composted by non-toxic and corrosion-resistant elements, presenting good biological compatibility. In this work, Plasma Electrolytic Oxidation (PEO) (using direct current-DC) was applied in conventional mode and Two-Step PEO aiming to produce a porous coating containing HA. It was not possible to produce a satisfactory coating applying conventional PEO due to successive spalling during the oxidation process. Adding a pretreatment to the conventional PEO changed the process to Two-Step PEO allowing to form a porous coating containing HA. The pretreatment was made by PEO using phosphoric electrolyte to produce a pre-coating. After that, the pre-coating was re-oxidized with calcium/phosphorus electrolyte. The Two-Step oxidized surface presented well-known good characteristics to applications in osseous implant devices such as porous formation, roughness in the micrometrical range, surface containing calcium and phosphorus, bioactive crystalline titanium oxide, and well-adhered HA formation. However, the coating morphology and chemical composition of pre-coating and Two-Step oxidized surfaces were not uniform. The non-uniformity of the Two-Step oxidized surface follows a similar non-uniformity pattern of the pre-coating surface. Two distinct morphologies were identified on the Two-Step oxidized surface: a "velvety morphology" with HA formation and a highly porous morphology. Regarding the Ti-25Nb-25Ta alloy, the Two-Step oxidation produced an adhered coating with porous apatite distribution interspersed with calcium-rich porous oxide. • Ti-25Nb-25Ta alloy was treated by Two-Step Plasma Electrolytic Oxidation (PEO) using DC mode. • The 1st step was made using electrolyte containing PO 4 -3 and the 2nd step using electrolyte containing Ca2+and PO 4 -3. • The phosphorus pre-coating played an important role in the formation of the well-adhered apatite coating. • The Two-Step oxidation produced a surface with good porous apatite distribution interspersed with calcium-rich porous oxide. [ABSTRACT FROM AUTHOR]