The NiTi alloy, known as Nitinol, represents one of the most investigated smart alloys, exhibiting a shape memory effect and superelasticity. These, among many other remarkable attributes, enable its utilization in various applications, encompassing the automotive industry, aviation, space exploration, and, notably, medicine. Conventionally, Nitinol is predominantly produced in the form of wire or thin sheets that allow producing many required components. However, the manufacturing of complex shapes poses challenges due to the tenacity of the NiTi alloy, and different processing routes at elevated temperatures have to be applied. Overcoming this obstacle may be facilitated by additive manufacturing methods. This article provides an overview of the employment of additive manufacturing methods, allowing the preparation of the required shapes of Nitinol products while retaining their exceptional properties and potential applications.

• Klíčová slova
• NiTi alloy, additive manufacturing, shape memory alloy,
• Publikační typ
• časopisecké články MeSH
• přehledy MeSH

Both poly(methyl methacrylate) (PMMA) and NiTi possess shape memory and biocompatibility behavior. The macroscale properties of PMMA-NiTi composites depend immensely on the quality of the interaction between two components. NiTi shape memory alloy (SMA) and superelastic (SE) sheets were spin coated on one side with PMMA. The composite was prepared by the spin coating method with an alloy-to-polymer-thickness ratio of 1:3. The bending stiffness and radius of curvature were calculated by using numerical and experimental methods during thermal cycles. The experimental radius curvatures in actuation have good agreement with the model. The change in shape results from the difference in coefficients of thermal expansion between PMMA and NiTi. Actuation temperatures were between 0 and 100 °C for the SMA-PMMA composite with a change in curvature from 10 to 120 mm with fixed Young's modulus of PMMA at 3 GPa, and a change in Young's modulus of NiTi from 30 to 70 GPa. PMMA-NiTi composites are useful as actuators and sensor elements.

• Klíčová slova
• NiTi, PMMA, curvature, radius, shape recovery, thermal cycles,
• Publikační typ
• časopisecké články MeSH

Metallic biomaterial alloys composed of nickel and titanium have unique thermal shape memory, superelastic, and high damping properties, which are widely used in the medicine. The major parameter evaluated in the studies regarding the behaviour of the material in the contact with organism or cells is biocompatibility. The aim of the studies is to clarify the differences in the proliferation, growth, and morphology especially in the cell cultures. The cytotoxicity is affected among other by release of the metal ions in the presence of the metal alloy, which is further dependent on the possible treatments of the material and the corrosive properties. To evaluate the cytotoxicity, wide range of tests including the Sulforhodamine B assay and MTT tests, expression profiles, cell survival tests such as apoptotic test are used. The review compares the cell behaviour in contact with the material alloys composed of nickel and titanium with respect to different materials composition and different surface treatment that affects the ion release. Even though the results published so far are controversial, almost all data suggest sufficient biocompatibility in medical use.

• Klíčová slova
• Alloy, Biocompatibility, Biomaterial, Cell, NiTi,
• MeSH
• apoptóza účinky léků   MeSH
• biokompatibilní materiály chemie   farmakologie   MeSH
• endoteliální buňky pupečníkové žíly (lidské) cytologie   účinky léků   fyziologie   MeSH
• kmenové buňky cytologie   účinky léků   fyziologie   MeSH
• krysa rodu Rattus MeSH
• kultivované buňky MeSH
• lidé MeSH
• myocyty hladké svaloviny cytologie   účinky léků   fyziologie   MeSH
• nádorové buněčné linie MeSH
• nikl chemie   farmakologie   MeSH
• proliferace buněk účinky léků   MeSH
• rhodaminy chemie   MeSH
• titan chemie   farmakologie   MeSH
• tuková tkáň cytologie   účinky léků   fyziologie   MeSH
• viabilita buněk účinky léků   MeSH
• zvířata MeSH
• Check Tag
• krysa rodu Rattus MeSH
• lidé MeSH
• zvířata MeSH
• Publikační typ
• časopisecké články MeSH
• práce podpořená grantem MeSH
• přehledy MeSH
• Názvy látek
• biokompatibilní materiály MeSH
• lissamine rhodamine B MeSH Prohlížeč
• nikl MeSH
• rhodaminy MeSH
• titan MeSH
• titanium nickelide MeSH Prohlížeč

Surface finish of NiTi is widely perceived to affect its biocompatibility and corrosion fatigue performance. The aim of this work was to find out, whether a carefully engineered surface oxide shows any beneficial effect over electropolished surface on the fatigue performance of superelastic NiTi wire mechanically cycled in simulated biofluid. Series of corrosion and environmental fatigue tensile tests was performed on superelastic NiTi wire with two different surface finishes frequently used in medical device industry. Open Circuit Potential reflecting the activity of chemical reactions on the surface of the wire cycled in electrochemical cell was continuously monitored during the fatigue tests. Microcracks at the surface of the fatigued NiTi wires were characterized by SEM and TEM. It was found that the carefully engineered 70 nm thick TiO2 oxide provides the NiTi wire with similar level of protection against the static corrosion as the less than 10 nm thin natural oxide on the electropolished wire and that it does not have any positive effect on its performance in environmental fatigue tests, whatsoever. On the contrary, the wire covered by the carefully engineered 70 nm thick TiO2 oxide displayed systematically poorer fatigue performance upon tensile cycling under specific critical loading conditions (strain amplitude <0.5% at large mean strains 1-7%).

• Klíčová slova
• Electrochemical corrosion tests, Environmental fatigue tests, Martensitic transformation, Nitinol, Shape memory alloy, Surface damage,
• MeSH
• koroze MeSH
• lidé MeSH
• ortodontické dráty MeSH
• oxidy * MeSH
• povrchové vlastnosti MeSH
• testování materiálů MeSH
• titan * MeSH
• únava MeSH
• zubní slitiny MeSH
• Check Tag
• lidé MeSH
• Publikační typ
• časopisecké články MeSH
• práce podpořená grantem MeSH
• Názvy látek
• oxidy * MeSH
• titan * MeSH
• zubní slitiny MeSH

Nickel-titanium alloy (nitinol, NiTi) is a biomaterial with unique thermal shape memory, superelasticity and high damping properties. Therefore NiTi has been used in medical applications. In this in vitro study, the effect of NiTi alloy (with two surface modifications - helium and hydrogen) on gene expression profile of selected interleukins (IL-1β, IL-6 and IL-8) and matrix metalloproteinases (MMP-1 and MMP-2) in human physiological osteoblasts and human osteoarthritic osteoblasts was examined to respond to a question of the different behavior of bone tissue in the implantation of metallic materials in the presence of cells affected by the osteoarthritic process. The cells were cultivated in contact with NiTi and with or without LPS (bacterial lipolysaccharide). Changes in expression of target genes were calculated by 2-ΔΔCt method. An increased gene expression of IL-1β in osteoarthritic osteoblasts, with even higher expression in cells collected directly from the metal surface was observed. In case of physiological osteoblasts, the change in expression was detected after LPS treatment in cells surrounding the disc. Higher expression levels of IL-8 were observed in osteoarthritic osteoblasts after NiTi treatment in contact with alloy, and in physiological osteoblasts without relation to location in combination of NiTi and LPS. IL-6 was slightly increased in physiological osteoblastes after application of LPS. MMP-1 expression level was obviously significantly higher in osteoarthritic osteoblasts with differences regarding the metal surface and location. MMP-2 expression was decreased in both cell lines after LPS treatment. In conclusion, results of present study show that the NiTi alloy and the treatment by LPS, especially repeated doses of LPS, change the gene expression of selected ILs and MMPs in human osteoblast cell cultures. Some of the changes were depicted solely to osteoarthritic osteoblasts.

• MeSH
• biokompatibilní materiály chemie   farmakologie   MeSH
• cytokiny MeSH
• kultivované buňky MeSH
• lidé MeSH
• lipopolysacharidy MeSH
• nikl farmakologie   MeSH
• osteoartróza * MeSH
• osteoblasty účinky léků   metabolismus   MeSH
• regulace genové exprese účinky léků   MeSH
• testování materiálů MeSH
• titan farmakologie   MeSH
• Check Tag
• lidé MeSH
• Publikační typ
• časopisecké články MeSH
• Názvy látek
• biokompatibilní materiály MeSH
• cytokiny MeSH
• lipopolysacharidy MeSH
• nikl MeSH
• titan MeSH
• titanium nickelide MeSH Prohlížeč

This paper deals with composite structures for biomedical applications. For this purpose, an architectured tubular structure composed of Nickel Titanium (NiTi) Shape Memory Alloy (SMA) and silicone rubber was fabricated. One of the main interests of such structures is to ensure a good adhesion between its two constitutive materials. A previous study of the authors (Rey et al., 2014) has shown that the adhesion between NiTi and silicone rubber can be improved by an adhesion promoter or plasma treatment. However, adhesion promoters are often not biocompatible. Hence, plasma treatment is favored to be used in the present study. Three different gases were tested; air, argon and oxygen. The effects of these treatments on the maximum force required to pull-out a NiTi wire from the silicone rubber matrix were investigated by means of pull-out tests carried out with a self-developed device. Among the three gases, a higher maximum force was obtained for argon gas in the plasma treatment. A tube shaped architectured NiTi/silicone rubber structure was then produced using this treatment. The composite was tested by means of a bulge test. Results open a new way of investigations for architectured NiTi-silicone structures for biomechanical applications.

• Klíčová slova
• Adhesion, Architectured composite, Biomedical applications, Filled silicone rubber, Interface, NiTi,
• MeSH
• argon chemie   MeSH
• kyslík chemie   MeSH
• nikl krev   chemie   MeSH
• pevnost v tahu MeSH
• silikonové elastomery chemie   MeSH
• slitiny chemie   MeSH
• testování materiálů MeSH
• titan krev   chemie   MeSH
• vzduch MeSH
• Publikační typ
• časopisecké články MeSH
• práce podpořená grantem MeSH
• Názvy látek
• argon MeSH
• kyslík MeSH
• nikl MeSH
• silikonové elastomery MeSH
• slitiny MeSH
• titan MeSH
• titanium nickelide MeSH Prohlížeč

To explore an effective route of customizing the superelasticity (SE) of NiTi shape memory alloys via modifying the grain structure, binary Ni55Ti45 (wt) alloys were fabricated in as-cast, hot swaged, and hot-rolled conditions, presenting contrasting grain sizes and grain boundary types. In situ synchrotron X-ray Laue microdiffraction and in situ synchrotron X-ray powder diffraction techniques were employed to unravel the underlying grain structure mechanisms that cause the diversity of SE performance among the three materials. The evolution of lattice rotation, strain field, and phase transformation has been revealed at the micro- and mesoscale, and the effect of grain structure on SE performance has been quantified. It was found that (i) the Ni4Ti3 and NiTi2 precipitates are similar among the three materials in terms of morphology, size, and orientation distribution; (ii) phase transformation happens preferentially near high-angle grain boundary (HAGB) yet randomly in low-angle grain boundary (LAGB) structures; (iii) the smaller the grain size, the higher the phase transformation nucleation kinetics, and the lower the propagation kinetics; (iv) stress concentration happens near HAGBs, while no obvious stress concentration can be observed in the LAGB grain structure during loading; (v) the statistical distribution of strain in the three materials becomes asymmetric during loading; (vi) three grain lattice rotation modes are identified and termed for the first time, namely, multi-extension rotation, rigid rotation, and nondispersive rotation; and (vii) the texture evolution of B2 austenite and B19' martensite is not strongly dependent on the grain structure.

• Klíčová slova
• Laue microdiffraction, bespoke NiTi shape memory alloys, grain structure, lattice rotation, multiscale, phase transformation, powder diffraction,
• Publikační typ
• časopisecké články MeSH

PURPOSE OF THE STUDY Nitinol (NiTi) is a biomaterial widely used in medicine based on super-elastic and shape memory properties. miR-124 has a key role in inflammatory process, osteoblasts differentiation, and mineralization. The aim of study was evaluating the differences in gene expression of miR-124 of human physiological osteoblasts (HOB) and human osteoarthritic osteoblasts (OSBA) as a response to NiTi alloy in different heat treatments. MATERIAL AND METHODS The cells were cultivated with NiTi discs with/without addition of bacterial lipopolysaccharide (LPS) for 72 hours. MicroRNAs were isolated, underwent reverse transcription and were analyzed by RT-PCR. RESULTS As a response to LPS, HOB overexpressed miR-124, while in OSBA expression change did not occur. Overexpression was also observed in both cell lines as a response to hydrogen and helium treated NiTi discs. HOB expressed significantly higher amount of miR-124 than OSBA as a response to hydrogen treatment of NiTi discs. In addition, hydrogen treatment caused significantly higher expression in HOB than LPS. The combination of NiTi disc and LPS treatment in HOB didn't cause any expression changes. Comparing to LPS-only treatment, the expression in HOB with combination of LPS and alloy was significantly lower. In OSBA, the expression was increased by the combination of LPS and hydrogen disc, in case of helium disc, the expression was decreased. CONCLUSIONS In conclusion, human physiological and osteoarthritic osteoblasts respond to NiTi alloy with both surface (hydrogen and helium atmosphere) treatment by overexpression of miR-124. The effect of LPS as inflammatory modulator suggests the presence of an "anti-inflammatory preconditioning" in osteoarthritic osteoblasts, as physiological osteoblasts overexpression was significantly higher. Key words: nitinol, osteoblast, miR-124, lipopolysaccharide.

• MeSH
• helium metabolismus   farmakologie   MeSH
• lidé MeSH
• lipopolysacharidy * farmakologie   metabolismus   MeSH
• mikro RNA * genetika   metabolismus   farmakologie   MeSH
• osteoartróza genetika   MeSH
• osteoblasty metabolismus   MeSH
• slitiny metabolismus   farmakologie   MeSH
• titan MeSH
• vodík metabolismus   farmakologie   MeSH
• Check Tag
• lidé MeSH
• Publikační typ
• časopisecké články MeSH
• Názvy látek
• helium MeSH
• lipopolysacharidy * MeSH
• mikro RNA * MeSH
• MIRN124 microRNA, human MeSH Prohlížeč
• nitinol MeSH Prohlížeč
• slitiny MeSH
• titan MeSH
• vodík MeSH

Nickel-titanium alloys have been used in medical applications for several years; however, biocompatibility of the material remains controversial. In the present study, the human umbilical vein endothelial cells (HUVEC) were cultured in contact with the nitinol used in two different heat treatment surface modifications-helium and hydrogen. The amount of Ni ions released from these alloys in contact with HUVEC was measured in media and in the cells by ICP-MS. An increased release of Ni ions was detected in He alloy compared with H2 alloy modification with an elevation with the metal exposition duration (24 h vs. 72 h). The cells contained the Ni ions in both selected alloy modifications with the lower levels in H2 alloys. To evaluate the potential of multiple metal applications, similar values were observed in media and in cell suspension for all surface modification combinations. The model analysis of effect of metal ion release on distant cells in the body showed that the concentration is interestingly similar to concentrations in cells in direct contact with the metal alloy. The cells are able to regulate the concentration of Ni ions within the cell. According to our best knowledge, the study for the first time describes the presence of Ni ions released from nitinol directly in the cells. In the case of the H2 modification, the lowest levels of Ni ions were detected both in medium and in the cells, which likely increases the biocompatibility of the nitinol alloy.

• Klíčová slova
• Biocompatibility, Biomaterial, Cell, Hydrogen modification, Nitinol,
• MeSH
• endoteliální buňky chemie   MeSH
• ionty chemie   MeSH
• lidé MeSH
• nikl * chemie   MeSH
• povrchové vlastnosti MeSH
• slitiny chemie   MeSH
• titan * chemie   MeSH
• Check Tag
• lidé MeSH
• Publikační typ
• časopisecké články MeSH
• Názvy látek
• ionty MeSH
• nikl * MeSH
• slitiny MeSH
• titan * MeSH

Despite the fundamental and technological importance of the elastic constants, a suitable method for their full characterization in epitaxial films is missing. Here we show that transient grating spectroscopy (TGS) with highly k-vector-selective generation and detection of acoustic waves is capable of determination of all independent elastic coefficients of an epitaxial thin film grown on a single-crystalline substrate. This experimental setup enables detection of various types of guided acoustic waves and evaluation of the directional dependence of their speeds of propagation. For the studied model system, which is a 3μm thin epitaxial film of the NiTi shape memory alloy on an MgO substrate, the TGS angular maps include Rayleigh-type surface acoustic waves as well as Sezawa-type and Love-type modes, delivering rich information on the elastic response of the film under different straining modes. The resulting inverse problem, which means the calculation of the elastic constants from the TGS maps, is subsequently solved using the Ritz-Rayleigh numerical method. Using this approach, tetragonal elastic constants of the NiTi film and their changes with the austenite→martensite phase transition are analyzed.

• Klíčová slova
• Elastic anisotropy, Epitaxial thin film, Guided acoustic waves, Inverse problem, Ritz–Rayleigh method, Shape memory alloys, Transient grating spectroscopy,
• Publikační typ
• časopisecké články MeSH