Simulated Body Fluid Test Research Articles

Corrosion resistance and biocompatibility of magnesium alloy with bioactive glass-reinforced hydrogel composite coatings

Magnesium (Mg) alloy is a promising candidate for biodegradable implants; however, its rapid degradation can create an unstable physiological environment that hampers tissue regeneration. To address this challenge, a polyvinyl alcohol (PVA) hydrogel composite reinforced with bioactive glass (BG) particles was developed as a coating for Mg alloy pellets, which underwent laser surface texturing (LST) and salting-out processes. results demonstrate that these treatments significantly enhance both the adhesiveness and swelling of the hydrogel coating. Notably, electrochemical corrosion assessments reveal a marked improvement in corrosion resistance, with the Mg–B1-L-S specimen exhibiting the highest performance after salting-out treatment. Electrochemical corrosion assessments revealed a significant enhancement in corrosion resistance for Mg alloy with the hydrogel coating, with the Mg–B1-L-S specimen showing superior performance following salting-out treatment. Immersion tests in simulated body fluid (SBF) confirmed the protective effect of the coatings, indicating that the addition of BG particles and salting-out treatment reduced mass loss and maintained pH stability. Biocompatibility evaluations through in vitro viability tests and osteogenic differentiation assays indicate that the Mg–B1-L and Mg–B1-L-S specimens exhibit superior cell activity, surface adhesion, and osteogenic potential. These findings highlight the effectiveness of PVA-BG hydrogel composite coatings in enhancing the corrosion resistance and biocompatibility of Mg alloy implants, positioning this approach as a significant advancement in the development of biodegradable materials for biomedical applications.

Enrichment of strontium and magnesium improves the physical, mechanical and biological properties of bioactive glasses undergoing thermal treatments: New cues for biomedical applications

Bioactive glasses (BGs) have emerged as invaluable resources for bone tissue engineering due to their remarkable properties such as bioactivity, resorbability, cell compatibility, and osteoconductivity. However, these materials exhibit certain limitations when subjected to high temperatures, for their tendency to crystallize, thus leading to diminished bioactivity, reduced mechanical strength, and altered dissolution kinetics. One promising approach to counteract this problem is to reduce the alkaline element content in BGs while simultaneously adding strontium and magnesium. Building on previous studies of Bio_MS, a recently developed experimental formulation, we investigated the contributions of strontium and magnesium to the thermal, mechanical, and biological properties of various bioactive glasses, including commercially available options. Differential thermal analysis, heating microscopy, X-ray diffractometry, environmental scanning electron microscopy, measurement of the Young's modulus, simulated body fluid testing, cytotoxicity tests, cell viability, growth, adhesion and morphology were assessed through an integrated approach and compared for a complete evaluation of BGs, and of doped BGs, also undergoing thermal treatments. The results demonstrated improved thermal, mechanical and biological behaviors of the magnesium-strontium-doped BGs, thus paving the way for the development of BGs with enhanced biomedical perspectives.

Evaluation of titanium dioxide and tantalum pentoxide nanoparticles for coating NiTi archwires in orthodontics: An in vitro study

Background: This study aims to enhance the biocompatibility of Nickel–Titanium (NiTi) alloy by developing a new coating using titanium dioxide (TiO2) and titanium pentoxide (Ta2O5) through direct current (DC) reactive sputtering technology. Materials and methods: Two distinct coating materials, namely, TiO2 and Ta2O5, were used to fabricate NiTi orthodontic archwires with improved surface properties. TiO2 nanoparticles, with thickness ranging from 21.90 nm to 31.93 nm, were deposited onto NiTi alloy substrates through DC reactive sputtering deposition under different power conditions. Results: X-ray diffraction and field emission scanning electron microscopy validated the uniformity and morphology of the coatings. Immersion tests in simulated body fluid (SBF) revealed significant hydroxyapatite layer growth on TiO2-coated NiTi, especially at a sputtering power of 240 W. Reduced nickel ion release was observed on TiO2 nanoparticles with a thickness of 21.90 nm at 50 W sputtering power compared with 31.93 nm-thick nanoparticles at 240 W. Ta2O5 thin films were deposited on NiTi substrates through DC magnetron reactive sputtering at ~100 °C with a deposition power of 50 W. Structural and morphological analyses through optical microscopy and X-ray diffraction, atomic force microscopy, and scanning electron microscopy revealed the homogeneity and low roughness of the coatings. Biocompatibility assessments in artificial saliva and SBF solutions established that Ta2O5-coated NiTi alloys exhibited superior electrochemical behavior, enhanced corrosion resistance, and diminished Ni ion release compared with uncoated specimens. Conclusion: TiO2 and Ta2O5 coatings not only improved the biocompatibility of NiTi orthodontic archwires but also presented a promising path for advanced biomedical applications. These coatings have potential in improving the cellular behavior and performance of NiTi-based orthodontic devices.

Characterization, mechanical, corrosion, and in vitro apatite-formation ability properties of hydroxyapatite-reduced graphene oxide coatings on Ti6Al4V alloy by plasma electrolytic oxidation

Hydroxyapatite-reduced graphene oxide (HA/rGO) nanocomposite coatings were developed on Ti6Al4V alloy using plasma electrolytic oxidation (PEO). The PEO electrolyte comprised calcium acetate (C4H6CaO4) and calcium glycerophosphate (C3H7O5CaP). Prior to integrating reduced graphene oxide into the coating solution, parameters such as voltage and current density were optimized using scanning electron microscopy (SEM). The influence of various current densities and graphene concentrations on coating properties was analyzed. Coating phase structures, surface morphologies, functional groups, and chemical compositions were characterized by X-ray diffraction (XRD), SEM, attenuated total reflectance-Fourier transform infrared spectroscopy (ATR-FTIR), and energy dispersive spectroscopy (EDS). Raman spectroscopy confirmed the presence of graphene in the coatings. Surface morphology examinations revealed that surface cracks appeared at voltages above 350 V due to thermal stresses. Increasing current density reduced the number of porosities but increased pore size. Adding graphene to the solution to form HA/rGO coatings further decreased both the number and size of porosities. XRD analysis identified phases of titanium, anatase, rutile, titanium phosphide, tri-calcium phosphate (TCP), and hydroxyapatite in the coatings. Corrosion properties were assessed via potentiodynamic polarization tests in simulated body fluid (SBF) solution. Tribological and mechanical properties were evaluated by pin-on-disk and microhardness, respectively. The in vitro apatite-formation ability of the coatings was assessed by immersion in SBF at 37 °C, with ion concentration changes measured by inductively coupled plasma spectrometry (ICP). Results indicated that increasing current density reduced porosities and increased the Ca/P ratio.

Fostering biomineralization and biodegradation: nano-hydroxyapatite reinforced iron composites for biodegradable implant application

Iron (Fe) is regarded as a candidate material for biodegradable metallic implants due to its biocompatibility and ability to degrade in physiological environemnt. However, the degradation rate in the physiological environment is too slow for clinical applications. It is necessary to accelerate the rate such that the degradation is compatible with tissue growth. Furthermore, the implant material needs to be bioactive for promoting osteointegration, osteoconductivity, cell proliferation and biological apatite formation. Nano-sized bioactive hydroxyapatite (nHA) was incorporated into a porous Fe matrix to enhance the bioactivity and degradation rate. Electrochemical studies in biomemtic NaCl solution, revealed that incorporation of nHA in porous Fe can increase the degradation by 2.5 times compared to the pure iron counterparts with similar porosity. Furthermore, immersion tests in simulated body fluid (SBF) revealed that nHA added samples displayed enhanced biomineralization and degraded at a rate three times faster than pure iron in this environment. The incorporation of nHA into the iron matrix aided in the formation of biomineralized hydroxyapatite. The composite surface promoted the cell adhesion and proliferation and the L929 fibroblast cells exhibited good cell viability. It is proposed that porous morphology incorporated with nHA can improve biomineralization and tailor the degradation rate of Fe-based materials in physiological environment.

Zinc-doped phosphate coatings for enhanced corrosion resistance, antibacterial properties, and biocompatibility of AZ91D Mg alloy

Magnesium and its alloys have been foreseen as promising bone-implant owing to good biocompatibility, high strength, mechanical properties, and biodegradability to replace the conventional bio-metals (Titanium, stainless-steel, Co-Cr alloys) in orthopedic applications. However, high corrosion rate and high degradation rates adversely effects like abrupt evolution of H2 gas and localized alkalization in a physiological environment limit its medical applications. To overcome these issues, phosphate-based surface coating is developed on Mg-alloy to resist the high biodegradation and corrosion rate utilizing magnesium substrate as source of magnesium ion through a single-step hydrothermal process. Controlling the fast corrosion rate and localized alkalization would reduce the antibacterial character of magnesium-based implants therefore, the simple phosphate-based coatings has been induced by doping it with zinc ions due to its physiological tolerance and excellent antibacterial efficacy. The doping of zinc ions may provide a sustained drug-free antibacterial characteristic for potential application in orthopedics. The synthesized phosphate-based coating was characterized using advanced techniques like Scanning Electron Microscopy, X-ray Diffraction, and wettability test, followed by comprehensive electrochemical testing to assess its corrosion behavior. The in vitro immersion test in simulated body fluid (SBF) indicates that deposition of phosphate and zinc doped phosphate coatings reduces the degradation rate consequently minimized the fast dissolution of Mg2+ ions and OH- in physiological environment. Additionally, cytotoxicity and biocompatibility were evaluated using Alamar Blue and live/dead assays on the MC3T3-E1 mouse osteoblast cell line. These assays demonstrated good cell viability, indicating the coatings possess favorable cytocompatibility and support cellular metabolic activity.

Zinc oxide coating impact on corrosion of ZK60 magnesium alloys in simulated body fluid

Magnesium alloys offer an alternative for applications in biodegradable implant devices within human body, eliminating the need for subsequent surgeries to remove metallic parts. Nevertheless, the uniform degradation rate of magnesium (Mg) alloys must be enhanced by applying surface coatings, preferably incorporating bactericidal and biocompatible agents, to improve the implant properties. In this study, magnesium alloys ZK60 (Mg, Zn, and Zr) and ZK60-Mm (Mg, Zn, and Zr with 1.5 % mass of rare-earth elements - mischmetal), both having a specific mass close to the bone, were investigated. The surfaces were coated with ZnO using physical vapor deposition (PVD) in the HiPIMS (High Power Impulse Magnetron Sputtering) mode. The corrosion resistance and degradation of the alloys were studied using electrochemical and immersion tests in simulated body fluid. Surface analysis and microstructures were characterized using Scanning Electron Microscopy (SEM), Energy Dispersive X-ray Spectroscopy (EDX), and X-ray Diffraction (XRD). The results showed that the ZnO coating favors osseointegration with hydroxyapatite formation after immersion in SBF. Moreover, electrochemical analysis indicates an enhancement in corrosion resistance. On average, the corrosion current density decreases by a factor of four for the ZK60 alloy and two for the ZK60-Mm alloy post-coating. The corrosion rate of ZnO-coated alloys is lower compared to that of uncoated alloys, showcasing the promising utility of this coating.

Microstructure, mechanical properties and bio-corrosion behavior of Mg–2Zn-0.3Ca-x (x= 0, 0.5, 1.0) Y alloys

Microstructure, mechanical properties, and bio-corrosion behavior of Mg–2Zn-0.3Ca-x (x = 0, 0.5, 1.0) wt.% Y series alloy have been investigated using microstructure observation, microhardness testing, tensile testing, immersion tests, and electrochemical measurements in simulated body fluid (SBF). The results show that the second phase's type, volume fraction, and distribution change with Y microalloying in the Mg–Ca–Zn alloys. The Mg–2Zn-0.3Ca (alloy 1) mainly comprises α-Mg and Ca2Mg6Zn3 phases. However, the amount of the Ca2Mg6Zn3 phase gradually decreases, and phases I (Mg3YZn6) and W (Mg3Y2Zn3) are also formed in Mg–2Zn-0.3Ca-0.5Y (alloy 2) and Mg–2Zn-0.3Ca–1Y (alloy 3), respectively. Furthermore, an increase in Y content to 1% refines the grains of alloy 1 leading to the improvement of microhardness (66.7 ± 4.2 HV), yield strength (141 ± 7 MPa), and ultimate tensile strength (385.7 ± 18 MPa) in alloy 3. The coarse and discontinuous eutectic phases (α-Mg + Ca2Mg6Zn3) in alloy 1 leads to accelerating the galvanic corrosion near the grain boundary. Moreover, polarization tests show that the addition of the rare earth element Y up to 0.5% in the alloy 2 leads to decreased corrosion current density (4.04 × 10−3 A cm−2) and the best anti-corrosion property as the result of formation of a protective corrosion product film.

Sputtered zirconium based metallic glassy thin films onto electrospun PCL nanofibrous scaffolds for enriching bioactivity

Surface modification of electrospun Polycaprolactone (PCL) nanoscaffold is to enhance surface properties, particularly bioactivity. In this paper, electrospinning was employed to produce PCL nanoscaffolds and enhancing the bioactivity of the electrospun PCL scaffolds by sputtering of Zirconium based thin film metallic glasses (Zr -TFMGs). The Energy Dispersive Spectroscopy (EDS) analysis exhibited the presence of Zr, Ti and Si and surface topography by Atomic Force Microscopy (AFM) revealed the smooth surface of metallic glasses with nanofibrous structures. The sputtered samples were subjected to immersion test in Simulated Body Fluid (SBF) to analyze the apatite forming ability of Zr–Ti–Si metallic glasses. After 21days of incubation, SEM clearly showed the spherical structures of apatite formed on the surface of modified electrospun PCL. Cell viability studies using L929 fibroblast cells indicates the higher proliferation rate for the Zr based TFMG sputtered PCL scaffold specimen than the uncoated neat PCL scaffold and indicating the bioactive nature of Zr based TFMG. Contact angle of TFMG sputtered sample exhibited the hydrophobic surface which is helpful in preventing the biomedical devices from blood coagulation.

The Effect of Iron Oxide Insertion on the In Vitro Bioactivity, and Antibacterial Properties of the 45S5 Bioactive Glass.

The aging population and increasing incidence of trauma among younger age groups have heightened the increasing demand for reliable implant materials. Effective implant materials must demonstrate rapid osseointegration and strong antibacterial properties to ensure optimal patient outcomes and decrease the chance of implant rejection. This study aims to enhance the bone-implant interface by utilizing 45S5 bioglass modified with various concentrations of Fe3O4 as a coating material. The effect of the insertion of Fe3O4 into the bioglass structure was studied using Raman spectroscopy which shows that with the increase in Fe3O4 concentration, new vibration bands associated with Fe-related structural units appeared within the sample. The bioactivity of the prepared glasses was evaluated using immersion tests in simulated body fluid, revealing the formation of a calcium phosphate-rich layer within 24 h on the samples, indicating their potential for enhanced tissue integration. However, the sample modified with 8 mol% of Fe3O4 showed low reactivity, developing a calcium phosphate-rich layer within 96 h. All the bioglasses showed antibacterial activity against the Gram-positive and Gram-negative bacteria. The modified bioglass did not present significant antibacterial properties compared to the bioglass base.

Highly bioactive hydroxyapatite coating made by flame spray technique

This research involves fabrication and characterization of flame sprayed hydroxyapatite (HA) coatings on 316 stainless steel substrates where the desirable structure with high porosity can be obtained. Nano-sized HA powder was synthesized and calcined at 600 °C. The subsequent powder was used as feedstock powder for flame spray technique (FS). In-flight particles of HA were spherical with the range of particle size between 3–37 µm. The average coating thickness was 128 µm and the crystalline phases were a mixture of HA and tricalcium phosphate (TCP). Simulated body fluid (SBF) test showed that HA layer was formed after 7 days. Highly bioactive properties were due to high surface area from rough coating and porous structure, which would be beneficial from the flame spray technique. The coating is promising for applications in biomedical field.

Exploring the Impact of Copper Oxide Substitution on Structure, Morphology, Bioactivity, and Electrical Properties of 45S5 Bioglass®.

In recent decades, the requirements for implantable medical devices have increased, but the risks of implant rejection still exist. These issues are primarily associated with poor osseointegration, leading to biofilm formation on the implant surface. This study focuses on addressing these issues by developing a biomaterial for implant coatings. 45S5 bioglass® has been widely used in tissue engineering due to its ability to form a hydroxyapatite layer, ensuring a strong bond between the hard tissue and the bioglass. In this context, 45S5 bioglasses®, modified by the incorporation of different amounts of copper oxide, from 0 to 8 mol%, were synthesized by the melt-quenching technique. The incorporation of Cu ions did not show a significant change in the glass structure. Since the bioglass exhibited the capacity for being polarized, thereby promoting the osseointegration effectiveness, the electrical properties of the prepared samples were studied using the impedance spectroscopy method, in the frequency range of 102-106 Hz and temperature range of 200-400 K. The effects of CuO on charge transport mobility were investigated. Additionally, the bioactivity of the modified bioglasses was evaluated through immersion tests in simulated body fluid. The results revealed the initiation of a Ca-P-rich layer formation on the surface within 24 h, indicating the potential of the bioglasses to enhance the bone regeneration process.

Design multifunctional Mg–Zr coatings regulating Mg alloy bioabsorption

Magnesium (Mg) alloys are widely used for temporary bone implants due to their favorable biodegradability, cytocompatibility, hemocompatibility, and close mechanical properties to bone. However, rapid degradation and inadequate strength limit their applicability. To overcome this, the direct current magnetron sputtering technique is employed for surface coating in Mg-based alloys using various zirconium (Zr) content. This approach presents a promising strategy for simultaneously improving corrosion resistance, maintaining biocompatibility, and enhancing strength without compromising osseointegration. By leveraging Mg's inherent biodegradability, it has the potential to minimize the need for secondary surgeries, thereby reducing costs and resources.This paper is a systematic study aimed at understanding the corrosion mechanisms of Mg–Zr coatings, denoted Mg-xZr (x = 0–5 at.%). Zr-doped coatings exhibited columnar growth leading to denser and refined structures with increasing Zr content. XRD analysis confirmed the presence of the Mg (00.2) basal plane, shifting towards higher angles (1.15°) with 5 at.% Zr doping due to lattice parameter changes (i.e., decrease and increase of “c” and “a” lattice parameters, respectively). Mg–Zr coatings exhibited “liquidphilic” behavior, while Young's modulus retained a steady value around 80 GPa across all samples. However, the hardness has significantly improved across all samples’ coating, reaching the highest value of (2.2 ± 0.3) GPa for 5 at.% Zr. Electrochemical testing in simulated body fluid (SBF) at 37 °C revealed a significant enhancement in corrosion resistance for Mg–Zr coatings containing 1.0–3.4 at.% Zr. Compared with the 5 at.% Zr coating which exhibited a corrosion rate of 32 mm/year, these coatings displayed lower corrosion rates, ranging from 1 to 12 mm/year. This synergistic enhancement in mechanical properties and corrosion resistance, achieved with 2.0–3.4 at.% Zr, suggests potential ability for reducing stress shielding and controlled degradation performance, and consequently, promising functional biodegradable materials for temporary bone implants.

Bioresorbable molybdenum temporary epicardial pacing wires

Cardiac pacing with temporary epicardial pacing wires (TEPW) is used to treat rhythm disturbances after cardiac surgery. Occasionally, TEPW cannot be mechanically extracted and remain in the thorax, where they may rarely cause serious complications like migration and infection. We aim to develop bioresorbable TEPW that will dissolve over time even if postoperative removal is unsuccessful. In the present study, we demonstrate a completely bioresorbable design using molybdenum (Mo) as electric conductor and the resorbable polymers poly(D, L-lactic-co-glycolic acid) (PLGA) and polycaprolactone (PCL) for electrically insulating double-coating. We compared the pacing properties of these Mo TEPW demonstrators to conventional steel TEPW in Langendorff-perfused rat hearts and observed similar functionality. In vitro, static immersion tests in simulated body fluid for up to 28 days elucidated the degradation behaviour of uncoated Mo strands and the influence of polymer coating thereon. Degradation was considerably reduced in double-coated Mo TEPW compared to the uncoated and the PLGA-coated condition. Furthermore, we confirmed good biocompatibility of Mo degradation products in the form of low cytotoxicity in cell cultures of human cardiomyocytes and cardiac fibroblasts. Statement of significanceTemporary pacing wires are routinely implanted on the heart surface to treat rhythm disturbances in the days following cardiac surgery. Subsequently, these wires are to be removed. When removal attempts are unsuccessful, wires are cut at skin level and the remainders are left inside the chest. Retained fragments may migrate within the body or become a centre of infection. These complications may be prevented using resorbable pacing wires. We manufactured completely resorbable temporary pacing wires using molybdenum as electrical conductor and assessed their function, degradation and biological compatibility. Our study represents an important step in the development of a safer approach to the treatment of rhythm disturbances after cardiac surgery.

The role of MgO on physical and bioactive properties of borophosphate glasses for biomedical applications

In this work, a novel series of borophosphate glasses of the system 40B2O3–25P2O5–(20-x)Na2O–15CaF2–xMgO (x = 0, 2.5, 5, 7.5, and 10 mol%) were synthesized using the melt-quenching technique. The effect of replacing Na2O with MgO in the glasses was analyzed by the physical and bioactive properties. The glasses were characterized by density, molar volume, X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), Differential thermal analysis (DTA), bioactivity tests in simulated body fluid (SBF), pH measurements, mass loss, and verification of cellular compatibility in RAW 247 murine macrophages. XRD and FTIR analyses were performed before and after immersion in SBF to verify the bioactivity. Density, molar volume and FTIR results before SBF showed structural changes in the glasses due to the addition of MgO. The pH and mass loss measurements allowed to verify the degradation behavior of the glass series as a function of MgO concentration. The DTA data showed an increase in Tg, Tx, and thermal stability due to the increase in MgO addition. XRD and FTIR analyses after SBF soaking showed superficial formation of apatites and other calcium phosphates of biological interest in the samples, attesting the bioactivity. Cytotoxicity assessed by MTT assay on the cell line RAW 247 showed that at a concentration of 500 μg/mL all glasses were compatible (non-cytotoxic). The results suggest that the synthesized glasses are bioactive, with the sample containing 5 mol% MgO exhibiting the bioactivity and biocompatibility required for biomaterial applications.

Investigations on the Degradation Behavior of Processed FeMnSi-xCu Shape Memory Alloys.

A new functional Fe-30Mn-5Si-xCu (x = 1.5 and 2 wt%) biomaterial was obtained from the levitation induction melting process and evaluated as a biodegradable material. The degradation characteristics were assessed in vitro using immersion tests in simulated body fluid (SBF) at 37 ± 1 °C, evaluating mass loss, pH variation that occurred in the solution, open circuit potential (OCP), linear and cyclic potentiometry (LP and CP), scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS) and nano-FTIR. To obtain plates as samples, the cast materials were thermo-mechanically processed by hot rolling. Dynamic mechanical analysis (DMA) was employed to evaluate the thermal properties of the smart material. Atomic force microscopy (AFM) was used to show the nanometric and microstructural changes during the hot rolling process and DMA solicitations. The type of corrosion identified was generalized corrosion, and over the first 3-5 days, an increase in mass was observed, caused by the compounds formed at the metal-solution interface. The formed compounds were identified mainly as oxides that passed into the immersion liquid. The degradation rate (DR) was obtained as a function of mass loss, sample surface area and immersion duration. The dynamic mechanical behavior and dimensions of the sample were evaluated after 14 days of immersion. The nanocompounds found on the surface after atmospheric corrosion and immersion in SBF were investigated with the Neaspec system using the nano-FTIR technique.

Developing micro-lamellar composites of magnesium-calcium deficient nanohydroxyapatite by powder metallurgy route: in vitro degradation studies

ABSTRACT In the present work, magnesium-calcium deficient nano hydroxyapatite (Mg-CDHA) lamellar composites with 5, 10 and 15 wt. % CDHA of crystallite size 32 nm were produced by ball milling and sintering. The Mg laminas were uniformly covered with CDHA crystals after 20 h of milling as confirmed by transmission electron microscopy. Enhanced biomineralisation was confirmed from X-ray diffraction method for the composites after 72 h of immersion in simulated body fluid (SBF). Degradation studies carried out by weight loss method and electrochemical tests in SBF clearly indicated the increased corrosion resistance for the composites with 10%HA compared to other combinations. The corrosion current values were observed as decreased (1.98 × 10−5 µA/cm2) for Mg-10%HA compared with other composites and pure Mg. Micro-lamellar structure and the deposited mineral phases from the simulated body fluids made the composite with 10% HA as optimum for biodegradable medical scaffold applications.

Study on mechanical and degradation behavior of Zn–Mn-xMg alloys under coupling effects of stress and SBF

Zinc-based implants will be subjected to combination of physiological corrosive media and stress during service in vivo. In this study, the mechanical and degradation behavior of Zn–Mn-xMg alloys under coupling effects of stress and simulated body fluid (SBF) were investigated. As a result, the ultimate tensile strength of Zn–Mn-xMg alloys decreased and incline to brittle fracture under the condition of slow strain rate tensile test in SBF. In addition, at a slower strain rate (1 × 10−6 s−1), the stress corrosion cracking susceptibility value will increase with the rise of Mg content. The immersion test under different compressive stresses shows that the corrosion will be inhibited under high pressure stress (50 MPa) compared with the lower one (10 MPa). The residual compressive strength of Zn-0.8Mn-xMg alloys decreases after immersion. A dense oxide layer could be induced with the increase of compressive stress, and it would inhibit the corrosion of the Zn-0.8Mn-xMg matrixes. These results indicate that Zn-0.8Mn-xMg alloys are expected to be a promising biodegradable material for biomedical applications.

Enhanced electrical properties of BNKT-BMN lead-free ceramics by CaSnO3 doping and their bioactive properties.

There is an increasing interest in using piezoelectric materials, including lead-free piezoceramics for medical applications. As a result, more attention has been placed on investigating the biological properties of these materials. In this research experiment, electrical, mechanical, and biological properties of lead-free 0.99Bi0.5(Na0.8K0.2)0.5TiO3-0.01Bi(Mg2/3Nb1/3)O3 or 0.99BNKT-0.01BMN doped with CaSnO3 (CSO) were investigated. The samples were synthesized by a modified solid-state reaction technique. X-ray diffraction (XRD) analysis showed that the samples presented a single perovskite phase. After adding CSO, electrical properties such as energy storage density (maximum W rec = 781 mJ cm-3) and electro-strain properties (maximum S max = 0.3%) were improved at room temperature. Mechanical properties were also enhanced for the modified samples with maximum values for Vickers hardness (H V) and elastic modulus (E m) of 6.11 GPa and 135 GPa, respectively. Biological assays for cytotoxicity, indicated that the samples had high cell viability, while the simulated body fluid (SBF) test revealed a moderate apatite forming ability. The samples were then coated with hydroxyapatite to improve their apatite-forming ability. The SBF testing for the coated samples showed that the coated samples had high apatite-forming ability. The obtained results pointed to the possibility of ceramics being used for multifunction electrical devices at room temperature and biomaterial applications.

Friction stir processing of AZ31 alloy to improve the mechanical, biodegradation, and in vitro biocompatible characteristics

The aim of the study was to improve the mechanical, biodegradation and in vitro biocompatible characteristics of as received rolled AZ31 (Mg-1%Zn-3%Al) alloy by develop the surface composite of Mg-Titania. The surface composite was developed by friction stir processing (FSP) and it’s used for prosthetic applications. The influence of tool rotation speed and number of FSP passes on grain structure, grain refinement, tensile strength, hardness, in vitro degradation rate and in vitro biocompatibility were explored. The obtained results support the capability of FSP in terms of mechanical strengthening, refinement of grain structure, dispersion of reinforcement (i.e. TiO2) and controlled degradation rate. Grain structure at stir zone, advancing side and retreating side were investigated. The large grains in the alloy were reduced to a fine equiaxial grains of average dimension of ≈ 3 μm by 3rd pass of FSP. The process was performed under two different tool rotation speed, i.e. 1550 and 2260 RPM. The addition of second phase in the matrix significantly improve the grain refinement. The results obtained from tensile test revealed the improvement in the percentage elongation without compromising the strength. The micro hardness of specimens of different parametric combination were evaluated and found ≈ 30–50% improvement in the micro hardness. The degradation rate by immersion test in simulated body fluid (SBF) for 3, 6 and 10 days were performed and found a significant reduction in degradation rate. The MTT assay for the biocompatibility performed by indirect method, the results validate the non-toxic behavior of processed specimen.