Oxidized Ti Surface Research Articles

Predominant surface property of an anodized titanium that enhances the cell response.

The aim of this study is to evaluate the predominant material property that enhances the biocompatibility of an anodized titanium (Ti) implant. A Ti surface was anodized in an H3PO4 electrolyte with various voltages. Then, the cell responses involving attachment, proliferation, and differentiation were evaluated. Anodization using various voltages formed TiO2 layers with various surface morphologies. All the anodized surfaces showed enhanced cell responses; however, the performance differences depending on the surface morphologies were minimal. In addition, enhanced cell responses were not observed on the thermally oxidized Ti surface, although a TiO2 layer was formed; therefore, the beneficial effect was derived from the TiO2 layer fabricated via anodization. Based on these findings, the topmost surface structure of the TiO2 layer predominantly influenced the cell behaviors because this property governed the important surface functions, such as hydrophilicity.

Metal-Oxide-Supported Ir-Decorated Electrocatalysts for Polymer Electrolyte Membrane Water Electrolysis

Introduction Since polymer electrolyte membrane water electrolysis (PEMWE) is similar in cell structure to polymer electrolyte fuel cells (PEFC), technologies used for PEFCs can be applied to PEMWEs. However, Pt electrocatalysts supported on carbon black (Pt/C) typically used for PEFCs cannot be applied under a high potential up to 2.0V [1]. Here, we apply SnO2 and titanium as alternative support materials. SnO2 may be promising as an anode electrocatalyst support material since it has relatively high electronic conductivity and stability against a high potential, among various metal oxides [2 ,3 ]. The top surface of metallic titanium is naturally oxidized to form stable titanium oxide, so that titanium supports may exhibit high durability under the strongly-acidic PEMWE condition [4]. In this study, we prepare the iridium-decorated SnO2/VGCF electrocatalysts (IrO2/Nb-SnO2/VGCF). Furthermore, by making such Ti sheet acting as the gas diffusion layer (GDL) and current collector, we prepare a GDL-integrated PEMWE electrode consisting of Ir electrocatalyst and Ti-based catalyst support (Ir/Ti). Experimental Sn0.98Nb0.02O2/VGCF was prepared via an ammonia co-precipitation method. IrO2 nanoparticles were decorated on Sn0.98Nb0.02O2/VGCF by evaporating the aqueous solution mixture containing Sn0.98Nb0.02O2/VGCF and H2IrCl6.nH2O while stirring, followed by heat treatment at 440°C in air. The Ti sheet was etched with 1M NaOH solution at 60°C for 1 hour, followed by heat treatment at 400°C in 5%H2-N2 for 30 minutes. Ir nanoparticles were decorated on the NaOH-etched Ti sheet by the arc plasma deposition (APD). The microstructure of the IrO2/Nb-SnO2/VGCF and the Ir/Ti sheet was observed by SEM, STEM, and TEM. Electrochemical measurements were made for the half cell and the single cell. Results and discussion We prepared IrO2/Sn(Nb)/VGCF with IrO2 loading of 23.6wt.%. Figure 1 shows the micrograph of the IrO2/Nb-SnO2/VGCF electrocatalyst. The micrograph indicates that Ir (or IrO2) nanoparticles have particle size of 1 to 3nm in diameter. I-V characteristics and durability of the MEA made with the IrO2/Sn(Nb)O2/VGCF electrocatalyst were evaluated. The MEA exhibited low activation overvoltage, but still with high IR loss and poor durability Figure 2 shows the STEM image of the Ir/Ti sheet after 2000 pulses of the APD with the Ir loading of 0.086mg/cm2, showing Ir particles of 1 to 2 nm on the etched Ti-based material. I-V characteristics of the MEA made with the Ir/Ti with the oxidized Ti surfaces were evaluated. The Ir/Ti MEA exhibited higher performance than that of the IrO2/Sn(Nb)O2/VGCF electrocatalyst despite very low Ir loading, indicating that the Ir/Ti MEA could be of interest for PEMWE applications.

Osteoclastic Response on Titanium Surfaces in Modified Simulated Body Fluid.

It was hypothesized that calcium phosphate (CaP) deposition onto Ti surfaces using biomimetic deposition contributed to not only improving osteogenesis but also suppressing osteoclastogenesis in terms of high surface hydrophilicity. Ti discs with two different surfaces were prepared: machined and anodic oxidized surfaces. The specimens of two different surfaces were soaked in modified simulated body fluid solution for 14 days at physiologic condition. Murine RAW 264.7 cells were utilized as osteoclast precursor cells. To evaluate osteoclast differentiation activity on Ti surfaces, tartrate-resistant acid phosphatase activity assay was conducted, and cells on Ti discs were investigated with a field emission-scanning electron microscope (FE-SEM). The expression of nuclear factor of activated T cells 1 (NFATc1) and c-Fos, two critical transcriptional factors involved in osteoclastogenesis, were also assessed in terms of mRNA and protein levels by real-time reverse transcriptase-polymerase chain reaction and western blot, respectively. Tartrate-resistant acid phosphatase activities on both machined and anodic oxidized Ti surfaces soaked in modified simulated body fluid were significantly lower compared with nonimmersed ones. FE-SEM observation showed that the number of differentiated osteoclasts was lower on anodic oxidized surfaces immersed in modified simulated body fluid compared with nonimmersed Ti surfaces. Protein and mRNA expression of NFATc1 and c-Fos were significantly decreased on anodic oxidized Ti surfaces immersed in modified simulated body fluid compared with those on nonimmersed ones. The effects of immersion of Ti discs in modified simulated body fluid on osteoclastogenesis were higher on anodic oxidized surfaces than on machined surfaces. It can be concluded that osteoclastogenesis was inhibited by biomimetic deposition using modified simulated body fluid, especially on anodic oxidized Ti surfaces.

Formation of highly stable self-assembled alkyl phosphonic acid monolayers for the functionalization of titanium surfaces and protein patterning.

A protocol for the preparation of improved phosphonate monolayers on a titanium (Ti) substrate is presented. Zirconium ions were used to enhance the bonding between the phosphonate headgroup and the pretreated Ti surface. Contact angle and X-ray photoelectron spectroscopy were used to characterize self-assembled monolayers (SAMs) of alkylphosphonic acid that formed spontaneously on Zr-mediated Ti (Zr/Ti) surfaces. The surfaces that were treated with an aqueous solution of zirconium oxychloride showed significantly enhanced stability in buffer compared with those formed directly on the native oxidized Ti. A bifunctional molecule, 10-mercaptodecanyl phosphonic acid (MDPA), was also used to form SAMs on Zr/Ti surfaces using an identical method, which enabled us to regulate the surface functionality through the terminal functional group. Protein patterning on the surface was carried out using UV irradiation through a mask to selectively degrade regions of the MDPA molecules. The surface was then backfilled with a protein-resistant molecule in the exposed regions followed by selective immobilization of proteins to the unexposed areas using a heterobifunctional linker molecule. The presented strategy significantly improved the stability of the phosphonate SAMs on oxidized Ti surfaces, which provided an ideal approach foundation for biomolecular immobilization and patterning onto the Ti surfaces. Thus, this method provided a versatile platform to activate the surfaces of biomedical Ti implants.

Immobilization of chitosan film containing semaphorin 3A onto a microarc oxidized titanium implant surface via silane reaction to improve MG63 osteogenic differentiation.

Improving osseointegration of extensively used titanium (Ti) implants still remains a main theme in implantology. Recently, grafting biomolecules onto a Ti surface has attracted more attention due to their direct participation in the osseointegration process around the implant. Semaphorin 3A (Sema3A) is a new proven osteoprotection molecule and is considered to be a promising therapeutic agent in bone diseases, but how to immobilize the protein onto a Ti surface to acquire a long-term effect is poorly defined. In our study, we tried to use chitosan to wrap Sema3A (CS/Sema) and connect to the microarc oxidized Ti surface via silane glutaraldehyde coupling. The microarc oxidization could formulate porous topography on a Ti surface, and the covalently bonded coating was homogeneously covered on the ridges between the pores without significant influence on the original topography. A burst release of Sema3A was observed in the first few days in phosphate-buffered saline and could be maintained for >2 weeks. Coating in phosphate-buffered saline containing lysozyme was similar, but the release rate was much more rapid. The coating did not significantly affect cellular adhesion, viability, or cytoskeleton arrangement, but the osteogenic-related gene expression was dramatically increased and calcium deposition was also abundantly detected. In conclusion, covalent bonding of CS/Sema could strongly improve osteogenic differentiation of osteoblasts and might be applied for Ti implant surface biofunctionalization.

Improvement of biological properties of titanium by anodic oxidation and ultraviolet irradiation

Abstract Anodic oxidation was applied to produce a homogeneous and uniform array of nanotubes of about 70 nm on the titanium (Ti) surface, and then, the nanotubes were irradiated by ultraviolet. The bioactivity of the Ti surface was evaluated by simulated body fluid soaking test. The biocompatibility was investigated by in vitro cell culture test. The results showed that bone-like apatite was formed on the anodic oxidized and UV irradiated Ti surface, but not on the as-polished Ti surface after immersion in simulated body fluid for two weeks. Cells cultured on the anodic oxidized Ti surface showed enhanced cell adhesion and proliferation, also presented an up-regulated gene expression of osteogenic markers OPG, compared to those cultured on the as-polished Ti surface. After UV irradiation, the cell behaviors were further improved, indicating better biocompatibility of Ti surface. Based on these results, it can be concluded that anodic oxidation improved the biological properties (bioactivity and biocompatibility) of Ti surface, while UV irradiation improved the biocompatibility to a better extent. The improved biological properties were attributed to the nanostructures as well as the enhanced hydrophilicity. Therefore, anodic oxidation combined with UV irradiation can be used to enhance the biological properties of Ti-based implants.

Surface characterization and corrosion behavior of micro-arc oxidized Ti surface modified with hydrothermal treatment and chitosan coating

In the present work, we describe the surface modification of commercially pure titanium (CP-Ti) by a composite/multilayer coating approach for biomedical applications. CP-Ti samples were treated by micro-arc oxidation (MAO) and subsequently some of the samples were coated with chitosan (Chi) by dip coating method, while others were subjected to hydrothermal treatment (HT) followed by chitosan coating. The MAO, MAO/Chi, and MAO/HT/Chi coated Ti were characterized and their characteristics were compared with CP-Ti. X-ray diffraction and scanning electron microscopy were used to assess the structural and morphological characteristics. The average surface roughness was determined using a surface profilometer. The corrosion resistance of untreated and surface modified Ti in commercial saline at 298K was evaluated by potentiodynamic polarization test. The results indicated that the chitosan coating is very well integrated with the MAO and MAO/HT coating by physically interlocking itself with the coated layer and almost sealed all the pores. The surface roughness of hydrothermally treated and chitosan coated MAO film was superior evidently to that with other sample groups. The corrosion studies demonstrated that the MAO, hydrothermally treated and chitosan coated sample enhanced the corrosion resistance of titanium. The result indicates that fabrication of hydrothermally treated MAO surface coatings with chitosan is a significant approach to protect the titanium from corrosion, hence enhancing the potential use of titanium as bio-implants.

A Classical Potential to Model the Adsorption of Biological Molecules on Oxidized Titanium Surfaces.

The behavior of titanium implants in physiological environments is governed by the thin oxide layer that forms spontaneously on the metal surface and mediates the interactions with adsorbate molecules. In order to study the adsorption of biomolecules on titanium in a realistic fashion, we first build up a model of an oxidized Ti surface in contact with liquid water by means of extensive first-principles molecular dynamics simulations. Taking the obtained structure as reference, we then develop a classical potential to model the Ti/TiOx/water interface. This is based on the mapping with Coulomb and Lennard-Jones potentials of the adsorption energy landscape of single water and ammonia molecules on the rutile TiO2(110) surface. The interactions with arbitrary organic molecules are obtained via standard combination rules to established biomolecular force fields. The transferability of our potential to the case of organic molecules adsorbing on the oxidized Ti surface is checked by comparing the classical potential energy surfaces of representative systems to quantum mechanical results at the level of density functional theory. Moreover, we calculate the heat of immersion of the TiO2 rutile surface and the detachment force of a single tyrosine residue from steered molecular dynamics simulations, finding good agreement with experimental reference data in both cases. As a first application, we study the adsorption behavior of the Arg-Gly-Asp (RGD) peptide on the oxidized titanium surface, focusing particularly on the calculation of the free energy of desorption.

Enhancement of octacalcium phosphate deposition on a titanium surface activated by electron cyclotron resonance plasma oxidation

The present study was designed to investigate whether the formation of octacalcium phosphate (OCP) is accelerated on titanium (Ti) surface by an electron cyclotron resonance (ECR) plasma oxidation at various pressures and temperatures. X-ray diffraction (XRD) of Ti-oxidized substrates showed that the rutile TiO(2) phase on its surfaces appeared at 300 degrees C and was crystallized when the oxidation temperature increased up to 600 degrees C. The thickness of TiO(2) film on the substrates increased progressively as the temperature increased. The oxidized Ti surfaces were soaked in calcium and phosphate solutions supersaturated with respect to both hydroxyapatite (HA) and OCP but slightly supersaturated with dicalcium phosphate dihydrate (DCPD). OCP crystals with a blade-like morphology were deposited as the primary crystalline phase on Ti substrates, while DCPD was included as a minor constituent. The amount of OCP deposition was maximized under 0.015 Pa in 300 degrees C. On the other hand, the oxidation temperature did not show a significant effect on the deposit in the range examined. The phase conversion from OCP to HA, determined by XRD, was demonstrated to occur even at 1 day and to advance until 7 days by immersing the Ti substrate with the deposit in simulated body fluid at 37 degrees C. The present results suggest that ECR plasma oxidation could be used to improve a Ti surface regarding its bioactivity due to the enhancement of osteoconductive OCP deposition.

Bioactive polymer grafting onto titanium alloy surfaces

Bioactive polymers bearing sulfonate (styrene sodium sulfonate, NaSS) and carboxylate (methylacrylic acid, MA) groups were grafted onto Ti6Al4V alloy surfaces by a two-step procedure. The Ti alloy surfaces were first chemically oxidized in a piranha solution and then directly subjected to radical polymerization at 70 °C in the absence of oxygen. The grafted surfaces were characterized by X-ray photoelectron spectroscopy (XPS), time-of-flight secondary ion mass spectrometry (ToF-SIMS) and the toluidine blue colorimetric method. Toluidine blue results showed 1–5 μg cm −2 of polymer was grafted onto the oxidized Ti surfaces. Grafting resulted in a decrease in the XPS Ti and O signals from the underlying Ti substrate and a corresponding increase in the XPS C and S signals from the polymer layer. The ToF-SIMS intensities of the S − and SO − ions correlated linearly with the XPS atomic percent S concentrations and the ToF-SIMS intensity of the TiO 3H 2 − ion correlated linearly with the XPS atomic per cent Ti concentration. Thus, the ToF-SIMS S −, SO − and TiO 3H 2 − intensities can be used to quantify the composition and amount of grafted polymer. ToF-SIMS also detected ions that were more characteristic of the polymer molecular structure (C 6H 4SO 3 − and C 8H 7SO 3 − from NaSS, C 4H 5O 2 − from MA), but the intensity of these peaks depended on the polymer thickness and composition. An in vitro cell culture test was carried out with human osteoblast-like cells to assess the influence of the grafted polymers on cell response. Cell adhesion after 30 min of incubation showed significant differences between the grafted and ungrafted surfaces. The NaSS grafted surfaces showed the highest degree of cell adhesion while the MA-NaSS grafted surfaces showed the lowest degree of cell adhesion. After 4 weeks in vivo in rabbit femoral bones, bone was observed to be in direct contact with all implants. The percentage of mineralized tissue around the implants was similar for NaSS grafted and non-grafted implants (59% and 57%). The MA-NaSS grafted implant exhibited a lower amount of mineralized tissue (47%).

Characterization of a bioactive nanotextured surface created by controlled chemical oxidation of titanium

Events at bone–implant interfaces are influenced by implant surface properties. Our previous work has revealed that osteogenic activity is enhanced by a nanotextured Ti surface, obtained by controlled chemical oxidation using a H 2SO 4/H 2O 2 mixture. To better understand the origin of this biological effect, we have carried out a characterization of the modified surface at the nanoscale. In particular, the morphology, structure, and chemical composition of the Ti surface were examined thoroughly. X-ray photoelectron spectroscopy (XPS), combined with grazing-angle Fourier-transform infrared (FTIR) spectroscopy, revealed that the oxidized Ti surface consists of almost pure TiO 2 with Ti:O ratio ranging between 1:2.02 and 1:2.08. Raman spectroscopy and X-ray diffraction (XRD) indicated that the chemically treated Ti surface is mainly composed of amorphous titania. Scanning electron microscopy (SEM) clearly showed that the treated Ti substrate becomes highly porous and has a surface consisting of nano-sized pits, which have average diameters and fractal dimensions ranging between 20–22 nm and 1.11–1.17, respectively. Atomic force microscopy (AFM) revealed a three–fold increase in surface roughness. The thickness of the oxide layer on the treated Ti surface is estimated to be ∼32–40 nm. Together, these observations provide a detailed characterization of chemically oxidized Ti surfaces at the nanoscale and offer new prospects for understanding and controlling the relationship between the properties of materials and their interactions with cells. Our work brings us closer to the creation of “intelligent” implant surfaces, capable of selectively influencing cell behavior.

Development and characterization of silane antisticking layers on nickel-based stamps designed for nanoimprint lithography

In this study we will report on the development of a process to establish antisticking layers on nickel-based stamps, which are used in several industrial applications of nanoimprint lithography or related methods. The fluorinated alkyl silane films have been deposited onto different Ni-based stamp surfaces in order to minimize the adhesion tendency at the stamp/polymer interface. Film thickness, chemical composition, purity, and binding mechanisms of the silane groups to different stamp surface materials have been determined by photoelectron spectroscopy (XPS). In the case of electroplated nickel stamps—where low imprint qualities are observed—multilayer thick films cover the stamp surfaces, consisting of polymerized, cross-linked alkyl silanes, which are poorly bound to the surface. In order to overcome these restrictions a 100 Å thick polycrystalline titanium layer has been established in a sandwich position between the nickel substrate and the silane film. Here, silane film thicknesses in the monomolecular region together with evidences for strong covalent linkage between the silane groups and the oxidized Ti surface can be concluded from the XPS results, leading to film properties and imprint qualities, which are comparable to those formerly observed for silicon stamps.

Deuterium uptake in titanium thin films: t ssc00621 the effect of oxide, and the metal (Ti and Fe) overlayers

Titanium thin films prepared in UHV were reacted with deuterium ( P D 2 〈1 × 10 −5 Torr ) to various loadings, as determined by microgravimetry using a quartz crystal microbalance. The kinetics of deuterium absorption favor a mechanism in which an α-phase surface deuteride forms on the film during the early stages of the reaction, resulting in a constant rate of deuterium uptake during most of the reaction. Surface characterization by AES and ELS, however, demonstrated spectral changes which were dependent on the bulk film stoichiometry. Electron-beam decomposition of the surface deuteride during AES analysis is postulated to explain this results. Oxidation of the titanium film surface caused a decrease in the deuterium absorption rate, completely inhibiting the reaction when oxide of thickness 20 Å or greater were formed. Fresh titanium layers on top of the oxide renewed the ability of the Ti film to take up D 2 at the previous rate. Iron adlayers were found to accelerate the D 2 absorption rate if Ti films, or to likewise reactive oxidized Ti surfaces.