Bioactive glass–ceramic coated titanium implants prepared by electrophoretic deposition

Surface modification of Ti alloys towards an improved osteoinductive behaviour is one of the major challenges in orthopaedic implant technology nowadays. One way to achieve this is by applying a bioactive coating which can increase the rate of osseointegration and chemical bonding of surrounding bone to the implant. In the present work, the production of a bioactive glass–ceramic coating on flat Ti alloys by electrophoretic deposition is demonstrated. The coatings are applied by cathodic deposition from non-aqueous suspensions followed by sintering in vacuum, avoiding uncontrolled oxidation of the Ti substrates. The use of non-aqueous suspensions both allowed to reduce the deposition time and yielded homogeneous coatings with a uniform thickness of 8 μm. Evaluation of the coating adhesion confirmed the good mechanical performance of the coatings with a tensile bond strength of 41.0 ± 11.1 MPa. Additionally, a feasibility study demonstrated the potential of electrophoretic deposition as a coating technique for commercial complex implants.     

Memory properties of a Ge nanoring MOS device fabricated by pulsed laser deposition

The non-volatile charge-storage properties of memory devices with MOS structure based on Ge nanorings have been studied. The two-dimensional Ge nanorings were prepared on a p-Si(100) matrix by means of pulsed laser deposition (PLD) using the droplet technique combined with rapid annealing. Complete planar nanorings with well-defined sharp inner and outer edges were formed via an elastic self-transformation droplet process, which is probably driven by the lateral strain of the Ge/Si layers and the surface tension in the presence of Ar gas. The low leakage current was attributed to the small roughness and the few interface states in the planar Ge nanorings, and also to the effect of Coulomb blockade preventing injection. A significant threshold-voltage shift of 2.5?V was observed when an operating voltage of 8?V was implemented on the device.     

In situ nitridation of titanium–molybdenum alloys during laser deposition

In situ nitridation during laser deposition of titanium–molybdenum alloys from elemental powder blends has been achieved by introducing the reactive nitrogen gas during the deposition process. Thus, Ti–Mo–N alloys have been deposited using the laser engineered net shaping (LENS^TM) process and resulted in the formation of a hard α(Ti,N) phase, exhibiting a dendritic morphology, distributed within a β(Ti–Mo) matrix with fine scale transformed α precipitates. Varying the composition of the Ar + N₂ gas employed during laser deposition permits a systematic increase in the nitrogen content of the as-deposited Ti–Mo–N alloy. Interestingly, the addition of nitrogen, which stabilizes the α phase in Ti, changes the solidification pathway and the consequent sequence of phase evolution in these alloys. The nitrogen-enriched hcp α(Ti,N) phase has higher c/a ratio, exhibits an equiaxed morphology, and tends to form in clusters separated by ribs of the Mo-rich β phase. The Ti–Mo–N alloys also exhibit a substantial enhancement in microhardness due to the formation of this α(Ti,N) phase, combining it with the desirable properties of the β-Ti matrix, such as excellent ductility, toughness, and formability.     

Correlation of in vitro and in vivo results of vacuum plasma sprayed titanium implants with different surface topography

Research has proven that rough surfaces improve both biologic and biomechanical responses to titanium (Ti) implants. The purpose of this study was to evaluate the correlation between the expression of bone cell-associated proteins to Vacuum Plasma-Sprayed Titanium implants (VPS-Ti) with different surface textures in vitro and the bone integration in vivo. The biological performances of the surfaces were evaluated over a period of 8 weeks using human bone marrow cell cultures and Göttinger mini pigs. Cells were cultured on VPS-Ti with two respectively different surface-roughnesses (Ra). The level of Osteoprotegerin (OPG), Osteocalcin (OC) and alkaline phosphatase activity (ALP) were evaluated. The bone integration in vivo was evaluated by histomorphological analyses. A cancellous structured titanium (CS-Ti) construct was used as reference material in both study designs. Comparison of data was conducted using the Scheffé tests and the paired t-test with Bonferroni’s correction. A comparative analysis was done to measure the degree of association between the in vitro and in vivo data. A total amount of OC was significantly increased for VPS-Ti for cells cultured on both VPS-Ti and CS-Ti, while OPG was only detectable after 8 weeks without any significant differences. The ALP activity on all surfaces was not statistically increased. For VPS-Ti with Ra ranging from 0.025 mm up to 0.059 mm, bone integration response was increased, but there was no statistical difference between the VPS-Ti. Expression of OPG, OC and ALP correlated with the histomorphological data over the 8-week period. The in vitro data suggest the superiority of VPS-Ti over CS-Ti, but more importantly, the biocompatibility of testing an in vitro model to predict the outcome and possible integration of implants in vivo.     

Formation of hydroxyapatite coating on titanium at 200°C through pulsed laser deposition followed by hydrothermal treatment

Pulsed laser deposition (PLD) has emerged as an acceptable technique to coat hydroxyapatite on titanium-based permanent implants for the use in orthopedics and dentistry. It requires substrate temperature higher than 400°C to form coatings of good adhesion and crystallinity. As this range of temperatures is likely to affect the bulk mechanical properties of the implant, lowering the substrate temperature during the coating process is crucial for the long-term performance of the implant. In the present study, hydroxyapatite target was ablated using a pulsed Nd:YAG laser (355 nm) onto commercially pure titanium substrates kept at 200°C. The coating thus obtained has been subjected to hydrothermal treatment at 200°C in an alkaline medium. The coatings were analysed using microscratch test, optical profilometry, scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS), X-ray diffraction (XRD) and infrared spectroscopy (FTIR). XRD, EDS and FTIR showed that the as-deposited coating contained amorphous calcium phosphate and the hydrothermal treatment converted it into crystalline hydroxyapatite. The micro-morphology was granular, with an average size of 1 micron. In the micro-scratch test, a remarkable increase in adhesion with the substrate was seen as a result of the treatment. The plasma plume during the deposition has been analysed using optical emission spectroscopy, which revealed atomic and ionic species of calcium, phosphorous and oxygen. The outcomes demonstrate the possibility of obtaining adherent and crystalline hydroxyapatite on titanium substrate at 200°C through pulsed laser deposition and subsequent hydrothermal treatment.     

Structural and optical properties of γ-alumina thin films prepared by pulsed laser deposition

Preparation of γ-alumina thin films by pulsed laser deposition from a sintered α-alumina target is investigated. The films were deposited on (100) silicon substrates at 973 K with varying oxygen partial pressures in the range 2.0 × 10⁻⁵-3.5 × 10^− 1 mbar. X-ray diffraction results indicated that the films were polycrystalline γ-Al₂O₃ with cubic structure. The films prepared in the oxygen partial pressure range 2.0 × 10^− 5-3.5 × 10^− 2 mbar contained nanocrystals of sizes in the range 10-16 nm, and became amorphous at pressures > 3.5 × 10^− 1 mbar. Topography of the films was examined by atomic force microscopy using contact mode and it showed the formation of nanostructures. The root-mean square surface roughness of the film prepared at 2.0 × 10^− 5 mbar and 3.5 × 10^− 1 mbar were 1.4 nm and 3.5 nm, respectively. The thickness and optical properties were studied using ellipsometry in the energy range 1.5-5.5 eV for three different angles of incidence. The refractive index was found to decrease from 1.81 to 1.73 with the increase of oxygen partial pressures from 2.0 × 10^− 5 to 3.5 × 10^− 2 mbar. The variation in the refractive index has been found to be influenced by the microstructure of the films obtained as a function of oxygen partial pressure.     

Transport properties of thin SnO2〈Sb〉 films grown by pulsed laser deposition

Thin SnO₂<Sb> films grown by pulsed laser deposition have been characterized by X-ray diffraction, optical spectroscopy, and scanning electron microscopy. The carrier mobility and concentration in the films have been determined as functions of target composition (0–8 at % Sb) using Hall effect measurements, and the resistivity of the films has been measured by a four-probe technique. The lowest resistivity (ρ = 2 × 10^?3 Ω cm) and the highest transmission (? 85%) of the films in the spectral range 400-800 nm have been obtained at a target composition Sb/(Sn + Sb) = 2 at %. The observed variation in the resistivity of the films is determined by changes in carrier concentration to a greater extent than by changes in carrier mobility. X-ray photoelectron spectroscopy results demonstrate that the predominant charge state of the antimony in the films is Sb⁵⁺.     

Biofunctionalization of porous titanium coatings through sol–gel impregnation with a bioactive glass–ceramic

In implant technology, open porous Ti coatings are applied as functional surface layers on prosthetic devices to improve osseointegration. Since a successful clinical performance strongly depends on the (initial) quality of bone ingrowth in the porous structure, surface functionalization of the porous Ti to incorporate an additional osteoconductive capacity is recommended. In this paper, a bioactive glass–ceramic coating is applied into the open porous network of Ti coatings with a pore throat size of 1–20 μm through a sol–gel process. Using an all-alkoxide precursor route, homogeneous amorphous powders of three- (SiO₂–CaO–P₂O₅) and four-component (SiO₂–CaO–Na₂O–P₂O₅) bioactive glass compositions are prepared. By sol impregnation followed by a heat treatment, it is possible to deposit a micrometer thin bioactive glass–ceramic layer on the walls of the internal pore surface, while the original porosity and the open pore structure of the Ti coatings are maintained. The tensile adhesion strength of the Ti/bioactive glass–ceramic composite coatings is 22 to 29 MPa, suggesting a good mechanical adhesion.     

In vitro blood and fibroblast responses to BisGMA–TEGDMA/bioactive glass composite implants

This in vitro study was designed to evaluate both blood and human gingival fibroblast responses to bisphenol A–glycidyl methacrylate–triethyleneglycol dimethacrylate (BisGMA–TEGDMA)/bioactive glass (BAG) composite, aimed to be used as composite implant abutment surface modifier. Three different types of substrates were investigated: (a) plain polymer (BisGMA 50 wt%–TEGDMA 50 wt%), (b) BAG–composite (50 wt% polymer + 50 wt% fraction of BAG–particles, <50 μm), and (c) plain BAG plates (100 wt% BAG). The blood response, including the blood–clotting ability and platelet adhesion morphology were evaluated. Human gingival fibroblasts were plated and cultured on the experimental substrates for up to 10 days, then the cell proliferation rate was assessed using AlamarBlue assay?. The BAG–composite and plain BAG substrates had a shorter clotting time than plain polymer substrates. Platelet activation and aggregation were most extensive, qualitatively, on BAG–composite. Analysis of the normalized cell proliferation rate on the different surfaces showed some variations throughout the experiment, however, by day 10 the BAG–composite substrate showed the highest (P < 0.001) cell proliferation rate. In conclusion, the presence of exposed BAG–particles enhances fibroblast and blood responses on composite surfaces in vitro.     

Precipitation of calcium phosphate in the presence of albumin on titanium implants with four different possibly bioactive surface preparations. An in vitro study

The aim of the present study was to compare the nucleating behaviour on four types of bioactive surfaces by using the simulated body fluid (SBF) model with the presence albumin. Titanium discs were blasted (B) and then prepared by alkali and heat treatment (AH), anodic oxidation (AO), fluoridation (F), or hydroxyapatite coating (HA). The discs were immersed in SBF with 4.5 mg/ml albumin for 3 days, 1, 2, 3 and 4 weeks and analysed with scanning electron microscopy/energy dispersive X-ray analysis (SEM/EDX) and X-ray photoelectron spectroscopy (XPS). Topographic surface characterisation was performed with a contact stylus profilometer. The results demonstrated that the bioactive surfaces initiated an enhanced calcium phosphate (CaP) formation and a more rapid increase of protein content was present on the bioactive surfaces compared to the blasted control surface. The observation was present on all bioactive surfaces. The fact that there was a difference between the bioactive surfaces and the blasted control surface with respect to precipitation of CaP and protein content on the surfaces support the fact that there may be biochemical advantages in vivo by using a bioactive surface.     

Characterization of β-Ga2O3 films deposited under different growth temperature by pulsed laser deposition

Journal of Materials Science: Materials in Electronics - A series of β-Ga2O3 films were prepared on polished Al2O3 substrates by pulsed laser deposition at temperatures between 580 and 780...     

Effect of beam interaction time on laser alloying with pulsed Nd–YAG laser

Abstract

Surface alloying of aluminium with nickel was carried out using a pulsed Nd–YAG laser. The effect of beam interaction time on laser alloying of aluminium with pulsed Nd–YAG laser has been studied. It was found that the beam interaction time of a pulsed laser has a significant effect on microstructure and properties of alloyed layers. The results indicated that with changes in the beam diameter, higher thickness of alloyed layer and higher microhardness are both obtained at a lower effective interaction time. When travel speed changes, the same conditions are obtained at a higher effective interaction time.     

Microwave characterization of nanostructured ferroelectric Ba(0.6)Sr(0.4)TiO(3) thin films fabricated by pulsed laser deposition

A series of nanostructured ferroelectric thin films of barium strontium titanate were fabricated using a pulsed laser deposition system with real-time in?situ process control. Pulsed laser deposition parameters were controlled during the growth of nanostructured thin films for use in the development of high frequency tunable microwave devices. The thin films were all grown at the same substrate temperature and laser beam energy density, but the chamber oxygen partial pressure (COPP) was varied systematically from 19?mTorr through 1000?Torr. Structural and electromagnetic characterization was performed using atomic force microscopy and evanescent microwave microscopy, respectively. Atomic force microscopy showed a linear increase in grain size with increases in the ambient oxygen pressure from 38 to 150?mTorr and from 300?mTorr to 1000?Torr. The correlation of the microwave properties with the epitaxial film microstructure can be attributed to stresses and polarizability in the film. Microwave characterization showed that a COPP of 75?mTorr yielded the most desirable film in terms of tunability and loss tangent over a wide frequency range.     

Biocompatibility of polyhydroxybutyrate microspheres: in vitro and in vivo evaluation

Microspheres have been prepared from the resorbable linear polyester of β-hydroxybutyric acid (polyhydroxybutyrate, PHB) by the solvent evaporation technique and investigated in vitro and in vivo. Biocompatibility of the microspheres has been proved in tests in the culture of mouse fibroblast cell line NIH 3T3 and in experiments on intramuscular implantation of the microspheres to Wistar rats for 3 months. Tissue response to the implantation of polymeric microspheres has been found to consist in a mild inflammatory reaction, pronounced macrophage infiltration that increases over time, involving mono- and poly-nuclear foreign body giant cells that resorb the polymeric matrix. No fibrous capsules were formed around polymeric microparticles; neither necrosis nor any other adverse morphological changes and tissue transformation in response to the implantation of the PHB microparticles were recorded. The results of the study suggest that polyhydroxybutyrate is a good candidate for fabricating prolonged-action drugs in the form of microparticles intended for intramuscular injection.     

Preparation of W–Sc2O3 targets and scandate cathodes with film prepared by pulsed laser deposition

Sub-micrometer Sc₂O₃–W powder with a narrow particle size distribution has been obtained by a sol–gel method combined with two-step hydrogen reduction process. Based on the obtained powder, the W–Sc₂O₃ targets have been sintered via spark plasma sintering (SPS) at 1300 °C. The W–Sc₂O₃ targets have the average grain size of about 1 μm. Both the sintering temperature and holding time are much lower than those of the targets prepared with micrometer sized powders. The obtained W–Sc₂O₃ targets have a high comparative density of 96.4% and rockwell hardness of 86.4 HRC. Using the target, the scandate cathode deposited with a film containing 5% Sc₂O₃ and 95% W has been obtained by pulsed laser deposition (PLD) method. This cathode has good emission property, i.e., the highest thermionic emission current density reaches 43.09 A/cm² of J_div at 900 °C_b after being activated for 8 h, which is much higher than that of scandate cathode without film. Scandium (Sc) supplied by the film on the surface during the activation forms a Ba–Sc–O active layer, which helps to the emission.     

In vivo performances of pure Zn and Zn–Fe alloy as biodegradable implants

The disadvantage of current biodegradable metals such as Mg and Fe is the release of hydrogen gas in vivo that can cause gas embolism and the production of voluminous iron oxide that can cause inflammation, respectively. Such considerations have turned focus towards Zn as an alternative. This is based on the fact that Zn plays a crucial role in many physiological processes, as well as potentially being biocompatible and capable of with biodegradation. As such, the purpose of the present study was to evaluate the in vivo performance of pure Zinc and Zn–2%Fe implants. The use of iron as an alloying element was aimed at accelerating the corrosion rate of pure zinc by a micro-galvanic effect so as to maintain the post-implantation biodegradation characteristics of the implant. In vivo assessment was carried out using cylindrical disks implanted in the back midline of 16 male Wistar rats for up to 24 weeks. Post-implantation evaluation included monitoring the well-being of rats, weekly examination of hematological parameters: serum Zn levels, red and white blood cell counts and hemoglobin levels, X-ray radiography, histological analysis and corrosion rate assessment. The results obtained in terms of well-being, hematological tests and histological analysis of the rats indicate that the in vivo behavior of pure Zn and Zn–2%Fe implants was adequate and in line with the results obtained by the control group containing inert Ti–6Al–4V alloy implants. The corrosion rate of Zn–2%Fe alloy in in vivo conditions was relatively increased compared to pure Zn due to micro-galvanic corrosion.

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In situ formation of titanium carbide in titanium powder compacts by gas–solid reaction

Porous titanium compacts of fine and coarse sponge titanium powders were reacted with methane gas to produce Ti–TiC in situ composites. The kinetics of titanium carbide formation during the reaction were studied in relation to powder size, reaction temperature and time, and methane flow rate. The titanium carbide was initially formed as a layer around each titanium powder and the rate of formation was found to be diffusion-controlled. Titanium hydride was also formed during the reaction but was easily removed by post-vacuum annealing. A significant reduction of chlorine content in the compact also resulted during the processing. High temperature vacuum sintering could densify the reacted compacts to over 95% theoretical density and, at the same time, alter the layered titanium carbide phase into rounded particles. It was possible to produce fully dense titanium base composites containing up to 30 vol% by the present gas–solid reaction-based processing.     

Physico-chemical and in vitro biological evaluation of strontium/calcium silicophosphate glass

Strontium is known to reduce bone resorption and stimulate bone formation. Incorporation of strontium into calcium phosphate bioceramics has been widely reported. In this work, calcium and calcium/strontium silicophosphate glasses were synthesized from the sol–gel process and their rheological, thermal, and in vitro biological properties were studied and compared to each other. The results showed that the gel viscosity and thus the rate of gel formation increased by using strontium in glass composition and by increasing aging temperature. In strontium-containing glass, the crystallization temperature increased and the type of the crystallized phase was different to that of strontium-free glass. Both glasses favored precipitation of calcium phosphate layer when they were soaked in simulated body fluid; however strontium seemed to retard the rate of precipitation slightly. The in vitro biodegradation rate of the strontium/calcium silicophosphate glass was higher than that of strontium-free one. The cell culture experiments carried out using rat calvaria osteoblasts showed that the incorporation of strontium into the glass composition stimulated proliferation of the cells and enhanced their alkaline phosphatase activity, depending on cell culture period.     

〈012〉-oriented growth of the films LaNiO3/SiO2/Si(111) by pulsed laser deposition

The highly 012-oriented LaNiO3 thin films were fabricated on SiO2coated Si(111) wafers by pulsed laser deposition at 690°C with a well prepared target. The stability of the interface and the smoothness of the surface were confirmed by scanning electron microscopy and atomic force microscopy. The electrical resistivity of the films at 300 K is 2.6 × 10–5m. The results of this work suggest that the films can be applied to the bottom electrode of ferroelectric memory devices.