Zinc (Zn) alloys seem to be promising candidates for application in orthopaedic or cardiovascular medical implants. In this area, high standards are required regarding the biocompatibility as well as excellent mechanical and tailored degradation properties. In the presented study, a novel Zn-0.8Mg-0.2Sr (wt%) alloy has been fabricated by the combination of casting, homogenization annealing and extrusion at 200 °C. As a consequence of its fine-grained homogenous microstructure, the prepared material is characterized by an excellent combination of tensile yield strength, ultimate tensile strength and elongation corresponding to 244 MPa, 324 MPa and 20% respectively. The in vitro corrosion rates of the Zn-0.8Mg-0.2Sr alloy in the physiological solution and the simulated body fluid were 244 μm/a and 69.8 μm/a, respectively. Furthermore, an extract test revealed that Zn-0.8Mg-0.2Sr extracts diluted to 25% had no adverse effects towards L929 fibroblasts, TAg periosteal cells and Saos-2 osteoblasts. Moreover, the Zn-0.8Mg-0.2Sr surface showed effective inhibition of initial Streptococcus gordonii adhesion and biofilm formation. These results indicated the Zn-0.8Mg-0.2Sr alloy, which has superior mechanical properties, might be a promising candidate for materials used for load-bearing applications.
V souvislosti s neúspěchem TEP kyčle typu kov-kov se oživil zájem o problematiku dlouhodobé akumulace kovů pocházejících z kloubní náhrady. Přitom je známo, že kovy se uvolňují také z ostatních typů kloubních náhrad, zejména mechanismem koroze. Kovy se dostávají do výpotku a do tkání, působí cytotoxicky, mohou indukovat změny DNA a stimulovat imunitní systém. Pravděpodobně nejdiskutovanějším tématem v souvislosti s kovy je alergická reakce a její podíl na předčasném selhání implantátu. Přes veškerý výzkum nepanuje v této otázce shoda. Některé vlivné odborné společnosti dokonce roli pozdní přecitlivělosti na kovy marginalizují a připouští pouze jako diagnózu per exclusionem. Obavy panují také z dlouhodobé akumulace kovů v těle, zejména u mladých pacientů. Nepodařilo se však prokázat ani genotoxický, ani kancerogenní efekt. Některé experimentální studie dokládají, že by se kovy uvolněné z povrchu kloubní náhrady mohly připojit k ostatním materiálům (polyetylen, kostní cement) při stimulaci nespecifické zánětlivé odpovědi, která se podílí na vzniku aseptického uvolnění a periprotetické osteolýzy. V článku jsou shrnuty současné pohledy na problematiku působení kovů na periprotetické tkáně i důsledky systémové zátěže.
In the context of metal-on-metal hip replacement failure, concerns regarding long-term accumulation of metals originating from joint replacement have been raised again. It is known at the same time that metals are released from other implant types as well, mainly by corrosion. Metals are released into surrounding tissues and joint fluid, produce cytotoxicity, stimulate immune reaction and can induce a DNA change. The most discussed topic regarding metals in joint arthroplasty probably is the allergic reaction and its contribution to premature implant failure. There still is no consensus on this topic despite all the research that has been made. Some clinical societies even marginalise the significance of late hypersensitivity and acknowledge the allergy only as a diagnosis of exclusion. So far, there is no definite evidence for a genotoxic or carcinogenic effect. Some experimental studies suggest that released metals in addition to other materials (polyethylene, bone cement) can take part in the innate immune response leading to periprosthetic osteolysis and aseptic loosening. This article summarises current views on the metal load effect on periprosthetic tissues and systemic metal burden effects.
- Klíčová slova
- pseudotumor,
- MeSH
- alergie diagnóza etiologie terapie MeSH
- artroplastiky kloubů škodlivé účinky MeSH
- biokompatibilní materiály škodlivé účinky MeSH
- biologické jevy MeSH
- cysty chemicky indukované diagnóza MeSH
- karcinogeneze MeSH
- koroze MeSH
- kovy * klasifikace krev škodlivé účinky MeSH
- lidé MeSH
- osteolýza chemicky indukované MeSH
- protézy kloubů * škodlivé účinky MeSH
- slitiny klasifikace škodlivé účinky MeSH
- Check Tag
- lidé MeSH
- Publikační typ
- práce podpořená grantem MeSH
- přehledy MeSH
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%).
- 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
The impact of four pre-treatment techniques on the surface morphology and chemistry, residual stress, mechanical properties, corrosion resistance in a physiological saline solution and cell colonization of commercially pure titanium is examined in detail. Mechanical polishing, electrochemical etching, chemical etching in Kroll's reagent, and ion sputter etching with argon ions were applied. Surface morphologies reflect the nature of surface layer removal. Significant roughening of the surface and a characteristic microtopology become apparent as a result of the sensitivity of chemical and ion sputter etching to the grain orientation. The hardness in the near surface region was controlled by the amount of residual stress. Etching of the stressed surface layer led to a reduction in residual stress and surface hardness. A compact passivation layer composed of TiO, TiO2 and Ti2O3 native oxides imparted high corrosion resistance to the surface after mechanical polishing, chemical and electrochemical etching. The ion sputter etched surface showed substantially reduced corrosion resistance, where the corrosion process was controlled by electron transfer. The specific topology affected the adhesion of the cell to the surface rather than the cell area coverage. The cell area coverage increased with the corrosion stability of the surface.
- MeSH
- buněčné linie MeSH
- elektrochemické techniky MeSH
- koroze MeSH
- lidé MeSH
- oxidy chemie MeSH
- povrchové vlastnosti MeSH
- testování materiálů MeSH
- titan chemie MeSH
- tvrdost MeSH
- Check Tag
- lidé MeSH
- Publikační typ
- časopisecké články MeSH
The Zn-based alloys, alloyed with the elements of the 2nd group of the periodic table, are considered as potential biodegradable materials suitable for the fabrication of small orthopaedic implants or cardiovascular stents. Unfortunately, the as-cast Zn-based alloys do not fulfil the requirements for mechanical properties for such applications. Extrusion is a thermomechanical process which is very powerful for breaking the cast microstructure and enhancing mechanical characteristics of metallic materials. In this study, we focused on the influence of extrusion parameters, such as temperature and extrusion ratio, on microstructural and mechanical characteristics of a ZnMg0.8Ca0.2 (wt.%) alloy. The extrusion led to a significant grain refinement and the formation of a crystallographic texture. Extrusion temperature played a more significant role in the mean grain size compared to the extrusion ratio (ER). At lower extrusion temperatures, the texture was less intensive and the subsequent mechanical anisotropy was weaker. Constants for the prediction of the grain size based on the Zener-Hollomon parameter were obtained. Prediction of mechanical properties using the Hall-Petch relationship appeared to be difficult because of the dependence of the texture on the extrusion temperature. Extrusion at the temperatures of 200 °C (ER = 25:1) and 150 °C (ER = 11:1) led to mechanical performance fulfilling the requirements for implantology.
- MeSH
- biokompatibilní materiály * MeSH
- koroze MeSH
- slitiny * MeSH
- stenty MeSH
- teplota MeSH
- Publikační typ
- časopisecké články MeSH
- práce podpořená grantem MeSH
We synthesized Fe foams using water suspensions of micrometric Fe2O3 powder by reducing and sintering the sublimated Fe oxide green body to Fe under 5% H2/Ar gas. The resultant Fe foam showed aligned lamellar macropores replicating the ice dendrites. The compressive behavior and deformation mechanism of the synthesized Fe foam were studied using an acoustic emission (AE) method, with which we detected sudden localized structural changes in the Fe foam material. The evolution of the deformation mechanism was elucidated using the adaptive sequential k-means (ASK) algorithm; specifically, the plastic deformation of the cell struts was followed by localized cell collapse, which eventually led to fracturing of the cell walls. For potential biomedical applications, the corrosion and biocompatibility characteristics of the two synthesized Fe foams with different porosities (50% vs. 44%) were examined and compared. Despite its larger porosity, the superior corrosion behavior of the Fe foam with 50% porosity can be attributed to its larger pore size and smaller microscopic surface area. Based on the cytotoxicity tests for the extracts of the foams, the Fe foam with 44% porosity showed better cytocompatibility than that with 50% porosity.
- MeSH
- akustika * MeSH
- biokompatibilní materiály chemie toxicita MeSH
- buněčné linie MeSH
- difrakce rentgenového záření MeSH
- elektrochemie metody MeSH
- fibroblasty MeSH
- koroze MeSH
- myši MeSH
- pevnost v tlaku MeSH
- poréznost MeSH
- testování materiálů MeSH
- viskoelastické látky chemie MeSH
- železité sloučeniny chemie MeSH
- železo chemie toxicita MeSH
- zvířata MeSH
- Check Tag
- myši MeSH
- zvířata MeSH
- Publikační typ
- časopisecké články MeSH
Dental implants are often made of titanium alloys. Implant therapy currently promises a good long-term result without impacting health; however, its success depends on many factors. In this article, the authors focus on the most common risk factors associated with metallic surgical implants. Titanium-induced hypersensitivity can lead to symptoms of implant rejection. Corrosion and biofilm formation are additional situations in which these symptoms may occur. For medical purposes, it is important to define and discuss the characteristics of metals used in implantable devices and to ensure their biocompatibility. To avoid hypersensitivity reactions to metallic dental implants, precautionary principles for primary prevention should be established.
- MeSH
- biokompatibilní materiály škodlivé účinky terapeutické užití MeSH
- koroze MeSH
- kovy škodlivé účinky terapeutické užití MeSH
- lidé MeSH
- rizikové faktory MeSH
- titan škodlivé účinky terapeutické užití MeSH
- zubní implantáty škodlivé účinky MeSH
- zubní slitiny škodlivé účinky terapeutické užití MeSH
- Check Tag
- lidé MeSH
- Publikační typ
- časopisecké články MeSH
- přehledy MeSH
This study investigates the morphology, microstructure, compressive behavior, biocorrosion properties, and cytocompatibility of magnesium (Mg)-aluminum (Al) alloy (AE42) scaffolds for their potential use in biodegradable biomedical applications. Mg alloy scaffolds were successfully synthesized via a camphene-based freeze-casting process with precisely controlled heat treatment. The average porosity was approximately 52% and the median pore diameter was ∼13 μm. Salient deformation mechanisms were identified using acoustic emission (AE) signals and adaptive sequential k-means (ASK) analysis. Twinning, dislocation slip, strut bending, and collapse were dominant during compressive deformation. Nonetheless, the overall compressive behavior and deformation mechanisms were similar to those of bulk Mg based on ASK analysis. The corrosion potential of the Mg alloy scaffold (-1.44 V) was slightly higher than that of bulk AE42 (-1.60 V), but the corrosion rate of the Mg alloy scaffold was faster than that of bulk AE42 due to the enhanced surface area of the Mg alloy scaffold. As a result of cytocompatibility evaluation following ISO10993-5, the concentration of the Mg alloy scaffold extract reducing cell growth rate to 50% (IC50) was 10.7%, which is higher (less toxic) than 5%, suggesting no severe inflammation by implantation into muscle.
The application of biodegradable magnesium-based materials in the biomedical field is highly restricted by their low fatigue strength and high corrosion rate in biological environments. Herein, we treated the surface of a biocompatible magnesium alloy AZ31 by severe shot peening in order to evaluate the potential of surface grain refinement to enhance this alloy's functionality in a biological environment. The AZ31 samples were studied in terms of micro/nanostructural, mechanical, and chemical characteristics in addition to cytocompatibility properties. The evolution of surface grain structure and surface morphology were investigated using optical, scanning and transmission electron microscopy. Surface roughness, wettability, and chemical composition, as well as in depth-microhardness and residual stress distribution, fatigue behaviour and corrosion resistance were investigated. Cytocompatibility tests with osteoblasts (bone forming cells) were performed using sample extracts. The results revealed for the first time that severe shot peening can significantly enhance mechanical properties of AZ31 without causing adverse effects on the growth of surrounding osteoblasts. The corrosion behavior, on the other hand, was not improved; nevertheless, removing the rough surface layer with a high density of crystallographic lattice defects, without removing the entire nanocrystallized layer, provided a good potential for improving corrosion characteristics after severe shot peening and thus, this method should be studied for a wide range of orthopedic applications in which biodegradable magnesium is used. STATEMENT OF SIGNIFICANCE: A major challenge for most commonly used metals for bio-implants is their non-biodegradability that necessitates revision surgery for implant retrieval when used as fixation plates, screws, etc. Magnesium is reported among the most biocompatible metals that resorb over time without adverse tissue reactions and is indispensable for many biochemical processes in human body. However, fast and uncontrolled degradation of magnesium alloys in the physiological environment in addition to their inadequate mechanical properties especially under repeated loading have limited their application in the biomedical field. The present study providesdata on the effect of a relatively simple surface nanocrystallziation method with high potential to tailor the mechanical and chemical behavior of magnesium based material while maintaining its cytocompatibility.
- MeSH
- elektrochemie MeSH
- koroze MeSH
- kultivované buňky MeSH
- lidé MeSH
- nanostruktury chemie ultrastruktura MeSH
- osteoblasty cytologie účinky léků MeSH
- povrchové vlastnosti MeSH
- slitiny farmakologie MeSH
- testování materiálů metody MeSH
- Check Tag
- lidé MeSH
- Publikační typ
- časopisecké články MeSH
- práce podpořená grantem MeSH
Material corrosion can be a limiting factor for different materials in many applications. Thus, it is necessary to better understand corrosion processes, prevent them and minimize the damages associated with them. One of the most important characteristics of corrosion processes is the corrosion rate. The measurement of corrosion rates is often very difficult or even impossible especially in less conductive, non-aqueous environments such as biofuels. Here, we present five different methods for the determination of corrosion rates and the efficiency of anti-corrosion protection in biofuels: (i) a static test, (ii) a dynamic test, (iii) a static test with a reflux cooler and electrochemical measurements (iv) in a two-electrode arrangement and (v) in a three-electrode arrangement. The static test is advantageous due to its low demands on material and instrumental equipment. The dynamic test allows for the testing of corrosion rates of metallic materials at more severe conditions. The static test with a reflux cooler allows for the testing in environments with higher viscosity (e.g., engine oils) at higher temperatures in the presence of oxidation or an inert atmosphere. The electrochemical measurements provide a more comprehensive view on corrosion processes. The presented cell geometries and arrangements (the two-electrode and three-electrode systems) make it possible to perform measurements in biofuel environments without base electrolytes that could have a negative impact on the results and load them with measurement errors. The presented methods make it possible to study the corrosion aggressiveness of an environment, the corrosion resistance of metallic materials, and the efficiency of corrosion inhibitors with representative and reproducible results. The results obtained using these methods can help to understand corrosion processes in more detail to minimize the damages caused by corrosion.
- MeSH
- elektrická vodivost terapeutické užití MeSH
- koroze * MeSH
- kovy chemie MeSH
- lidé MeSH
- Check Tag
- lidé MeSH
- Publikační typ
- audiovizuální média MeSH
- časopisecké články MeSH
- práce podpořená grantem MeSH
