Key Engineering Materials Vol. 587

Abstract: In this study, bilayered silk and silk/nanoCaP scaffolds were developed for osteochondral tissue engineering. Aqueous silk solution (16 wt.%) was used for preparation of the cartilage-like layer and, for generation of the silk/nanoCaP suspension and the bottom layer (CaP/Silk: 16 wt.%). The scaffolds were formed by using salt-leaching/lyophilization approach. The scanning electron microscopy revealed that the both layers presented porous structure and integrated well. Micro-computed tomography images confirmed that the CaP phase was only retained in the silk/nanoCaP layer. The hydration degree and mechanical properties of the bilayered scaffold were comparable to the ones of each single layer. The apatite crystal formation was limited to the silk/nanoCaP layer, when soaking the scaffold in a simulated body fluid solution, which is a must for the application of the developed scaffolds in OC tissue engineering.

Abstract: In order to induce bone regeneration several natural and synthetic materials have been proposed. However, single-phase scaffolds present some insurmountable disadvantages such as poor mechanical strength or brittleness and too low or too high degradation rate. In order to overcome these drawbacks, composite systems can be an interesting and promising option. In the present work a novel hybrid porous scaffold for bone tissue engineering is proposed. Chitosan/Forsterite (Ch/FS) composite scaffolds were prepared by freeze-drying method using a chitosan/forsterite ratio of 90/10. The FS nanopowder (Mg₂SiO₄) is synthesized using a simple solgel based method. The FS composition was checked by XRD analysis. The macrostructure of the Ch/FS scaffolds were analyzed by SEM, the FS distribution within the chitosan matrix observed by EDS, the mechanical strength measured by compression test in PBS and the biocompatibility of the composite on human osteosarcoma cell line (MG-63) verified by MTT assay after 48 hours. The porosity appears interconnected and with a pore size ranging from 1 to 100 μm. The FS is overall distributed within the chitosan matrix. The compression strength of composite scaffolds increased with respect to the pure chitosan scaffolds of more than two times (from 0.8 to 1.9 KPa) and the composites did not show any toxicity effect on human osteosarcoma cells.

Abstract: It has been shown that hydrogel bilayered scaffolds combining cartilage- and bone-like layers are most advantageous for treating osteochondral defects. In this study, it is proposed the use of low acyl gellan gum (LAGG) for developing bilayered hydrogel scaffolds for osteochondral tissue engineering. The cartilage-like layer of the GG-based bilayered hydrogel scaffolds is composed of LAGG (2 wt%). By adding a 2 wt% LAGG aqueous solution to different amounts of HAp (5-20 wt%) it was possible to produce the bone-like layer. In vitro bioactivity tests were performed by means of soaking the LAGG/LAGG-HAp hydrogel scaffolds in a simulated body fluid solution up to 14 days. Scanning electron microscopy, Fourier transform infra-red spectroscopy and X-ray diffraction analyses demonstrated that apatite formation is limited to the bone-like layer of the LAGG/LAGG-HAp bilayered hydrogel scaffolds.

Abstract: Multicomponent bioactive nanostructured films (MuBiNaFs) with an excellent combination of chemical, mechanical, tribological, and biological properties were developed and deposited by sputtering of composite targets produced via the self-propagating high-temperature synthesis method. Reviewed substrate materials included Ti-, Ni-, and Co-based alloys, insoluble polymers, and deimmunized donors bones. Our results showed that the MuBiNaF deposition can be effectively combined with either a bulk material modification to improve its mechanical properties, or a surface modification to control surface roughness and blind porosity. Among other promising applications, the fabrication of hybrid materials incorporated with stem cells or medicine is mentioned.

Abstract: Bioactive Ti metal able to release Sr ions was prepared by chemical and heat treatments of Ti metal. Ti metal was initially soaked in 5M NaOH solution to form sodium hydrogen titanate. It was soaked in a mixed solution of CaCl₂ and SrCl₂ to replace its Na ions with Ca and Sr ions at a given range from 0.18 to 1.62 in Sr/Ca ratio. When it was heat-treated at 600 oC, it formed Sr-containing calcium titanate (SrCT) and rutile. The apatite formation in SBF of the treated metal was low, but increased markedly by subsequently soaking the metal in 1 M SrCl₂ solution at 80 oC. Thus, the treated metal gradually released Sr ions into phosphate-buffered saline up to 0.9 ppm. It is expected that the Ti metal formed with the bioactive SrCT layer could release Sr ions in a living body to promote bone formation, and bond to a living bone through an apatite.

Abstract: In this work, TiSiN coatings were selected to improve the adhesion between dental ceramic and CoCr substrate. The coatings were prepared by the cathodic arc technique in N₂ reactive atmosphere, at different bias voltages, and analyzed for elemental composition, surface roughness, wettability and corrosion resistance in Fusayama Meyer artificial saliva. After the coating deposition, low-fusing dental ceramic film was fired on coated alloy, using a dental furnace. The bond strength of these specimens was tested using a 3-point bending test.

Abstract: The surface of Ti6Al4V alloys was activated by a selective laser microstructuring and subsequent sintering of hydroxyapatite (HAp) nanopowders into the generated structures. For structuring, a novel q-switched CO₂ laser with pulse durations of about 600 ns and a peak power of up to 60 kW was used. This laser system provides defined blind holes and channel-like geometries with structural sizes in the range of 100-500 μm. The influence of different process gases (Ar, O₂, N₂) on the formation of titanium oxide (TiO₂) and titanium nitride (TiN) interfaces during laser structuring was investigated by GDEOS. HAp nanopowders prepared by a wet-chemical synthesis route were subsequently sintered into the generated structures using a CO₂ laser with continuous radiation intensities up to 2·10² W/cm². The homogeneously sintered structures consist of HAp as the major phase and minor amounts of tricaliumphosphate (TCP) and tetracalciumphophate (TTCP). The formation of TCP and TTCP during laser sintering can be minimized by adjusting sintering parameters (time, laser intensity) and by applying additional process gases (O₂, Ar).

Abstract: Titanium alloys corresponding to Ti-Nb-Zr-Ta system represent a new generation of biomaterials, which were developed for medical applications like metal-ceramic. They are composed of non-toxic and non-allergenic elements and have lower values of modulus of elasticity compared to that of the current biomaterials used in dentistry or orthopedics. In this paper are presented two new titanium alloys (Ti-21Nb-6Zr-15Ta and Ti-25Nb-10Zr-8Ta), which were characterized from structural aspect, mechanical and surface properties point of view using scanning electron microscopy, X-ray diffraction, wear properties, Vickers microhardness measurement. Also, was tested the cytotoxicity of these alloys using direct contact method. The results showed that the investigated alloys have a biphasic structure composed of β-solid solution with intragranular lamellar structures specific to α^”. The experimental results shown that new titanium alloys from the system Ti-Nb-Zr-Ta present much better properties compared to that of the metallic biomaterials used currently.

Abstract: The present paper put in evidence the influence of applying different heat treatments on some metallic materials such as cobalt and titanium alloys, usualy used for medical applications. The alloys were cobalt base alloy type CoCrMo (22%Cr, 6%Mo, rest Co), in nontreated state, quenching at 1100°C /1h/aer, quenching at 1100°C /1h/air+ sensiblizing at 550°/4h/ air, 600°/4h/air and/or 650°C/4h/air and titanium base alloys - alloy TiMo0.3Ni0,7 (0.23%Mo, 0.72%Ni, Ti rest), alloy TiAl5Fe2V2Mo1,5 (1.52%Mo, 5.15%Al, 2.56%Fe, 2.35%V, Ti rest), each of them in non treated state, annealing at 1050°C/1h/air and annealing at 850°C/1h/air. Corrosion tests were made at potentiostat-galvanostat AUTOLAB, in Ringer solution (for both alloys) and NaCl infusion solution (only for cobalt base alloy) by drawing the polarization curves. Our conclusion is that by applying correct and proper heat treatments to both at cobalt alloys and in titanium alloys there is an improving of the corrosion resistance.

Abstract: In this paper we report on the preparation and characterization of hydroxyapatite coatings deposited on Ti6Al4V alloy by magnetron sputtering deposition method. The amorphous deposited coatings were thermal annealed in a flux of dry nitrogen and water vapours at 800 °C for 30 and 120 minutes, in order to investigate the effect of this treatment on surface roughness, corrosion resistance and wettability. The films were characterized by surface profilometry, electrochemical tests and contact angle measurements. After annealing, the hydroxyapatite coatings became crystalline, exhibiting rougher surfaces, higher corrosion resistance and lower contact angles. We have demonstrated that the hydroxyapatite coating annealed at 800°C for 30 minutes represents a good candidate to be used for medical implants, due to its superior corrosion behaviour and good wettability.