Search Results (20)

The effect of cross- or unidirectional rolling on the microstructure, corrosion rate, texture, and hemolysis of the Mg-0.5Zn-0.25Ga and Mg-1.5Zn-0.375Ga alloys was evaluated. After both rolling processes, the microstructure of the as-cast alloys was considerably refined due to the recrystallization process, obtaining higher grain refinement after cross-rolling. The Mg-1.5Zn-0.375Ga alloy showed a finer microstructure than the Mg-0.5Zn-0.25Mg alloy due to the effect of both the severe plastic deformation obtained after cross-rolling and the higher amount of alloying elements, which act as grain refiners. After unidirectional rolling, the texture intensity of the basal plane increases, while the cross-rolled alloys show lower texture intensity due to the activation of the pyramidal and/or prismatic slip systems. The cross-rolled alloys showed a higher corrosion rate than the unidirectionally rolled alloys due to the basal texture developed. The Mg-1.5Zn-0.375Ga alloy showed a higher corrosion rate than the Mg-0.5Zn-0.25Ga alloy since the voids formed during heat treating were not fully eliminated during rolling. The Mg-0.5Zn-0.25Ga alloy after unidirectional rolling was not hemolytic (4.7%) and showed the lowest corrosion rate (0.8 mm/y). Thus, this alloy may be an excellent candidate for use in the fabrication of biodegradable implants. Full article

Background/Objectives: Guided bone regeneration (GBR) requires barrier membrane materials that balance biodegradation with mechanical stability. Magnesium (Mg)-based metals have good prospects for use as biodegradable barrier materials due to their elastic modulus, good biocompatibility, and osteogenic properties. In this study, gallium (Ga) was introduced into Mg to enhance the mechanical strength and optimize the degradation behavior of the alloy, addressing the limitations of conventional magnesium alloys in corrosion control and strength retention. Methods: Mg-xGa alloys (x = 1.0–3.0%, wt.%) were evaluated for biocompatibility, degradation, and osteogenic potential. Corrosion rates were calculated via weight loss, Mg²⁺ release, and pH changes. Osteogenic effects were assessed using rat bone marrow mesenchymal stem cells (rBMSCs) for alkaline phosphatase (ALP) activity, extracellular matrix (ECM) mineralization, and osteogenic-related gene expression. Optimal alloy was fabricated into barrier membranes with different pore sizes (0.85–1.70 mm) for the rabbit mandibular defect to evaluate the porosity effect on new bone formation. Results: Cytocompatibility tests established a biosafety threshold for Ga content below 3 wt.%. Mg-1Ga demonstrated uniform corrosion with a rate of 1.02 mm/year over 28 days. In vitro, Mg-1Ga enhanced ALP activity, ECM mineralization, and osteogenic gene expression. The 1.70 mm pore size group exhibited superior new bone formation and bone mineral density at 4 and 8 weeks. Conclusions: These results highlight Mg-1Ga’s biocompatibility, controlled degradation, and osteogenic properties. Its optimized pore design bridges the gap between collagen membranes’ poor strength and titanium meshes’ non-degradability, offering a promising solution for GBR applications. Full article

Magnesium and its alloys represent promising candidates for biomedical implants due to their biodegradability and mechanical properties, which are similar to natural bone. However, their rapid degradation process characterized by dynamic pH fluctuations and significant hydrogen gas evolution during biocorrosion adversely affects both in vitro and in vivo assessments. While the ISO 10993-5 and 12 standards provide guidelines for evaluating the in vitro biocompatibility of biodegradable materials, they also introduce testing variability conditions that yield inconsistent results. To address these inherent characteristics of Mg alloys, developing improved methods that accurately simulate the physiological environment for in vitro biocompatibility testing is essential. This study introduces two novel extraction approaches for evaluating Mg alloys: a buffered solution utilizing PBS/DMEM with quaternary dilutions and a modified ISO standard protocol employing decuple dilution of conventional unbuffered extracts. The present findings establish that controlled optimization of extraction conditions, specifically buffer composition and dilution parameters, enables reliable in vitro cytotoxicity assessment of Mg alloys, providing a robust methodology that advances the preclinical evaluation of these promising biodegradable materials. Full article

Magnesium alloys are considered as promising materials for use as biodegradable implants due to their biocompatibility and similarity to human bone properties. However, their high corrosion rate in bodily fluids limits their use. To address this issue, amorphization can be used to inhibit microgalvanic corrosion and increase corrosion resistance. The Mg-Zn-Ga metallic glass system was investigated in this study, which shows potential for improving the corrosion resistance of magnesium alloys for biodegradable implants. According to clinical tests, it has been demonstrated that Ga ions are effective in the regeneration of bone tissue. The microstructure, phase composition, and phase transition temperatures of sixteen Mg-Zn-Ga alloys were analyzed. In addition, a liquidus projection of the Mg-Zn-Ga system was constructed and validated through the thermodynamic calculations based on the CALPHAD-type database. Furthermore, amorphous ribbons were prepared by rapid solidification of the melt for prospective alloys. XRD and DSC analysis indicate that the alloys with the most potential possess an amorphous structure. The ribbons exhibit an ultimate tensile strength of up to 524 MPa and a low corrosion rate of 0.1–0.3 mm/year in Hanks’ solution. Therefore, it appears that Mg-Zn-Ga metallic glass alloys could be suitable for biodegradable applications. Full article

To further improve the mechanical properties and corrosion resistance of the biodegradable magnesium (Mg) alloy, the Mg-4Zn-0.5Sr-xAg alloy (x = 0.2 wt.%, 0.5 wt.%, 1.0 wt.%, and 2.0 wt.%) was smelted in vacuum under the protection of inert gas. The effect of the Ag content on the microstructure and mechanical properties of Mg-4Zn-0.5Sr was tested. The results show that the comprehensive properties of Mg-4Zn-0.5Sr-0.5Ag are best. The grain size of the Mg-4Zn-0.5Sr-0.5Ag alloy is minimal, that is, 83.28 μm. The average tensile strength (σ_b), yield strength (σ_s), elongation (ε), and hardness for the Mg-4Zn-0.5Sr-0.5Ag alloy is 168.00 MPa, 88.00 MPa, 12.20%, and 59.90 HV, respectively. To further improve the properties of cast Mg-4Zn-0.5Sr-0.5Ag alloy, extruding treatment was conducted. After extrusion deformation, the grain size of the alloy was significantly refined to 9 μm; at the same time, fine second phases were formed and evenly distributed in the matrix. And then, the mechanical properties of the alloy are significantly enhanced due to the effect of fine crystal strengthening and dispersion strengthening. The σ_b, σ_s, ε, and hardness value for the extruded Mg-4Zn-0.5Sr-0.5Ag alloy are 236.00 MPa, 212.00 MPa, 18.97%, and 65.42 HV, respectively. Under the synergistic action of adding the Ag element and extrusion treatment, the grain size of the alloy was significantly refined and the coarse second phase in the alloy became refined to disperse in the matrix, which benefits the formation of electric couples characterized as small cathode–large anode between the second phase and Mg matrix. During full immersion, corrosion products covered on the large anode surface could reduce the galvanic corrosion tendency. Full article

Fixation screws and other temporary magnesium alloy fixation devices are used in orthopedic practice because of their biodegradability, biocompatibility and acceptable biodegradation rates. The substitution of dissolving implant by tissues during the healing process is one of the main requirements for biodegradable implants. Previously, clinical tests showed the effectiveness of Ga ions on bone tissue regeneration. This work is the first systematic study on the corrosion rate and biocompatibility of Mg–Zn–Ga–(Y) alloys prepared by hot extrusion, where Ga is an additional major alloying element, efficient as a bone-resorption inhibitor. Most investigated alloys have a low corrosion rate in Hanks’ solution close to ~0.2 mm/year. No cytotoxic effects of Mg–2Zn–2Ga (wt.%) alloy on MG63 cells were observed. Thus, considering the high corrosion resistance and good biocompatibility, the Mg–2Zn–2Ga alloy is possible for applications in osteosynthesis implants with improved bone tissue regeneration ability. Full article

Magnesium (Mg) alloys have recently attracted attention in biomedicine as biodegradable materials with non-toxic degradable products. Such compounds have become a frontier in the study of biodegradable materials because of their remarkable biomechanical compatibility and superior biocompatibility. The use of Mg-based implants reduces the negative consequences of permanent biological implants by eliminating the necessity for biomaterial surgery following the healing process. However, the quick deterioration, formation of considerable gas of hydrogen volumes and a rise in the body environment pH are obstacles in the application of Mg as an implant material. Hence, compelling advances for erosion resistance and biocompatibility of magnesium and its alloys are noteworthy. Surface modification may be a practical approach because it improves the erosion resistance compared with extensive preparation of a treated surface for progressed bone recovery and cell attachment. Coating produced by plasma electrolytic oxidation (PEO) seems a compelling method in order to enhance magnesium and the properties of its alloys. PEO-formed coatings cannot provide long-term protection in the physiological environment due to their porous nature. Thus, a polymer coating is applied on the porous PEO-formed coating, which is steadily applied on the surface. Polymer coatings improve the biocompatibility properties of Mg and its alloys and increase corrosion resistance. In this article, the most recent advancements in PEO/polymer composite coatings are reviewed, and the biocompatibility of such coatings is examined. Full article

The development direction of bioresorbable fixing structures is currently very relevant because it corresponds to the priority areas in worldwide biotechnology development. Magnesium (Mg)-based alloys are gaining high levels of attention due to their promising potential use as the basis for fixating structures. These alloys can be an alternative to non-degradable metal implants in orthopedics, maxillofacial surgery, neurosurgery, and veterinary medicine. In our study, we formulated a Mg-2Zn-2Ga alloy, prepared pins, and analyzed their biodegradation level based on SEM (scanning electron microscopy) and EDX (energy-dispersive X-ray analysis) after carrying out an experimental study on rats. We assessed the resorption parameters 1, 3, and 6 months after surgery. In general, the biodegradation process was characterized by the systematic development of newly formed bone tissue. Our results showed that Mg-2Zn-2Ga magnesium alloys are suitable for clinical applications. Full article

Magnesium alloys are attractive candidates for use as temporary fixation devices in osteosynthesis because they have a density and Young’s modulus similar to those of cortical bone. One of the main requirements for biodegradable implants is its substitution by tissues during the healing process. In this article, the Mg–Zn–Ga–(Y) alloys were investigated that potentially can increase the bone growth rate by release of Ga ions during the degradation process. Previously, the effectiveness of Ga ions on bone tissue regeneration has been proved by clinical tests. This work is the first systematic study on the microstructure and mechanical properties of Mg–Zn–Y alloys containing Ga as an additional major alloying element prepared by the hot-extrusion process. The microstructure and phase composition of the Mg–Zn–Ga–(Y) alloys in as-cast, heat-treated, and extruded conditions were analyzed. In addition, it was shown that the use of hot extrusion produces Mg–Zn–Ga–(Y) alloys with favorable mechanical properties. The tensile yield strength, ultimate tensile strength, and elongation at fracture of the MgZn4Ga4 alloy extruded at 150 °C were 256 MPa, 343 MPa, and 14.2%, respectively. Overall, MgZn4Ga4 alloy is a perspective for applications in implants for osteosynthesis with improved bone regeneration ability. Full article

(1) Background: Resorbable Mg-based implants represent a new direction in orthopedic surgery but have some drawbacks, such as their rapid biodegradation and increased rate of corrosion. Some in vitro studies hypothesized that tissue necrosis, incision dehiscence, risk of gas embolization in vital organs, interference with coagulation processes, and trophocyte viability impairment can occur. (2) Methods: We conducted an in vivo study on ten rabbit cases, in two groups; group one, consisting of six cases, received cylindrical implants of Mg–1Ca alloy in tibial intramedullary bone tissue. Group two, consisting of four cases, received Mg–1Ca parallelepiped implants, in the thigh muscular tissue. We recorded and compared weight (preoperatively and at 2, 4, and 6 weeks postoperatively), complete blood count, serum electrolytes, liver and kidney functional markers, and coagulation parameters, prior to and at 6 weeks after surgery. Local evolution was assessed radiologically and with tissue biopsies with complete pathology analysis. (3) Results: All biological markers and clinical evolution were favorable, showing good integration of the implants with none of the local or systemic signs of degradation. (4) Conclusions: Our study shows that the clinical use of Mg–1Ca bioresorbable alloys can be safe as none of the cited local or systemic complications have been identified. Full article

The attractiveness of Zn-based alloys as structural materials for biodegradable implants mainly relates to their excellent biocompatibility, critical physiological roles in the human body and excellent antibacterial properties. Furthermore, in in vivo conditions, they do not tend to produce hydrogen gas (as occurs in the case of Mg-based alloys) or voluminous oxide (as occurs in Fe-based alloys). However, the main disadvantages of Zn-based alloys are their reduced mechanical properties and their tendency to provoke undesirable fibrous encapsulation due to their relatively high standard reduction potential. The issue of fibrous encapsulation was previously addressed by the authors via the development of the Zn-2%Fe alloy that was selected as the base alloy for this study. This development assumed that the addition of Fe to pure Zn can create a microgalvanic effect between the Delta phase (Zn₁₁Fe) and the Zn-matrix that significantly increases the biodegradation rate of the alloy. The aim of the present study is to examine the effect of up to 0.8% Mn on the mechanical properties of biodegradable Zn-2%Fe alloy and to evaluate the corrosion behavior and cytotoxicity performance in in vitro conditions. The selection of Mn as an alloying element is related to its vital role in the synthesis of proteins and the activation of enzyme systems, as well as the fact that Mn is not considered to be a toxic element. Microstructure characterization was carried out by optical microscopy and scanning electron microscopy (SEM), while phase analysis was obtained by X-ray diffraction (XRD). Mechanical properties were examined in terms of hardness and tensile strength, while corrosion performance and electrochemical behavior were assessed by immersion tests, open circuit potential examination, potentiodynamic polarization analysis and impedance spectroscopy. All the in vitro corrosion testing was performed in a simulated physiological environment in the form of a phosphate-buffered saline (PBS) solution. The cytotoxicity performance was evaluated by indirect cell viability analysis, carried out according to the ISO 10993-5/12 standard using Mus musculus 4T1 cells. The obtained results clearly demonstrate the strengthening effect of the biodegradable Zn-2%Fe alloy due to Mn addition. The effect of Mn on in vitro corrosion degradation was insignificant, while in parallel Mn had a favorable effect on indirect cell viability. Full article

Magnesium (Mg)-based degradable alloys have attracted substantial attention for tissue engineering applications due to their biodegradability and potential for avoiding secondary removal surgeries. However, insufficient data in the existing literature regarding Mg’s corrosion and gas formation after implantation have delayed its wide clinical application. Since the surface properties of degradable materials constantly change after contact with body fluid, monitoring the behaviour of Mg in phantoms or buffer solutions could provide some information about its physicochemical surface changes over time. Through surface analysis and spectroscopic analysis, we aimed to investigate the structural and functional properties of degradable disks. Since bubble formation may lead to inflammation and change pH, monitoring components related to acidosis near the cells is essential. To study the bubble formation in cell culture media, we used a newly developed Mg alloy (based on Mg, zinc, and calcium), pure Mg, and commercially available grade 2 Titanium (Ti) disks in Dulbecco’s Modified Eagle Medium (DMEM) solution to observe their behaviour over ten days of immersion. Using surface analysis and the information from near-infrared spectroscopy (NIRS), we concluded on the conditions associated with the medical risks of Mg alloy disintegration. NIRS is used to investigate the degradation behaviour of Mg-based disks in the cell culture media, which is correlated with the surface analysis where possible. Full article

Binary MgCa alloys are one of the promising and well investigated biodegradable metals and therefore a good standard for the study of novel processing routes. In this investigation, novel powder metallurgical (PM) blending and sintering methods were applied for the generation of biodegradable MgCa test specimens, using metal injection moulding (MIM). In addition to the classical PM-blending route using Ca-containing master-alloys, Ca-containing ceramics and hydrides, as there are CaO and CaH_2, were used separately and in a stoichiometric mixture. In situ X-ray synchrotron radiation experiments were performed for a deeper understanding of alloy forming mechanisms during sintering. Mechanical and degradation performance was investigated by tensile testing and the monitoring of biodegradation under physiological conditions. Besides its sound strength of up to 144 MPa and degradation rate of 0.25 mm/a, the new redox alloying technique avoids the usage of any greenhouse active SF₆ gas (global warming potential 22,800) during alloying, keeping the earth’s atmosphere safer. Therefore, it can be concluded that Ca-containing ceramics and hybrids are attractive alternatives to obtain, comparable to Mg-based materials, thus enabling safer processing. Full article

Mg alloys have mechanical properties similar to those of human bones, and have been studied extensively because of their potential use in biodegradable medical implants. In this study, the influence of different heat treatment regimens on the microstructure and mechanical and corrosion properties of biodegradable Mg–Zn–Ga alloys was investigated, because Ga is effective in the treatment of disorders associated with accelerated bone loss. Solid–solution heat treatment (SSHT) enhanced the mechanical properties of these alloys, and a low corrosion rate in Hanks’ solution was achieved because of the decrease in the cathodic-phase content after SSHT. Thus, the Mg–4 wt.% Zn–4 wt.% Ga–0.5 wt.% Y alloy after 18 h of SSHT at 350 °C (ultimate tensile strength: 207 MPa; yield strength: 97 MPa; elongation at fracture: 7.5%; corrosion rate: 0.27 mm/year) was recommended for low-loaded orthopedic implants. Full article

Mg-based biodegradable materials, used for medical applications, have been extensively studied in the past decades. The in vitro cytocompatibility study showed that the proliferation and viability (as assessed by quantitative MTT-assay—3-(4,5-dimethyltiazol-2-yl)-2,5-diphenyl tetrazolium bromide) were not negatively affected with time by the addition of Mn as an alloying element. In this sense, it should be put forward that the studied alloys don’t have a cytotoxic effect according to the standard ISO 10993-5, i.e., the level of the cells’ viability (cultured with the studied experimental alloys) attained both after 1 day and 5 days was over 82% (i.e., 82, 43–89, 65%). Furthermore, the fibroblastic cells showed variable morphology (evidenced by fluorescence microscopy) related to the alloy sample’s proximity (i.e., related to the variation on the Ca, Mg, and Mn ionic concentration as a result of alloy degradation). It should be mentioned that the cells presented a polygonal morphology with large cytoplasmic processes in the vicinity of the alloy’s samples, and a bipolar morphology in the remote region of the wells. Moreover, the in vitro results seem to indicate that only 0.5% Mn is sufficient to improve the chemical stability, and thus the cytocompatibility; from this point of view, it could provide some flexibility in choosing the right alloy for a specific medical application, depending on the specific parameters of each alloy, such as its mechanical properties and corrosion resistance. In order to assess the in vivo compatibility of each concentration of alloy, the pieces were implanted in four rats, in two distinct body regions, i.e., the lumbar and thigh. The body’s reaction was followed over time, 60 days, both by general clinical examinations considering macroscopic changes, and by laboratory examinations, which revealed macroscopic and microscopic changes using X-rays, CT(Computed Tomography), histology exams and SEM (Scanning Electron Microscopy). In both anatomical regions, for each of the tested alloys, deformations were observed, i.e., a local reaction of different intensities, starting the day after surgery. The release of hydrogen gas that forms during Mg alloy degradation occurred immediately after implantation in all five of the groups examined, which did not affect the normal functionality of the tissues surrounding the implants. Imaging examinations (radiological and CT) revealed the presence of the alloy and the volume of hydrogen gas in the lumbar and femoral region in varying amounts. The biodegradable alloys in the Mg-Ca-Mn system have great potential to be used in orthopedic applications. Full article