Development of Rapid Bioactivity-Expressed Zr-50Ti Alloys by Surface Treatment with Modified Simulated Body Fluid.

Zr-50Ti alloys are promising biomaterials due to their excellent mechanical properties and low magnetic susceptibility. However, Zr-50Ti alloys do not inherently bond well with bone. This study aims to enhance the bioactivity and bonding strength of Zr-50Ti alloys for orthopedic implant materials. Initially, the surface of Zr-50Ti alloys was treated with a sulfuric acid solution to create a microporous structure, increasing surface roughness and area. Subsequently, low crystalline calcium phosphate (L-CaP) precipitation was controlled by adding Mg2+ and/or CO32- ions in modified simulated body fluid (m-SBF). The treated Zr-50Ti alloys were then subjected to cold isostatic pressing to force m-SBF into the micropores, followed by incubation to allow L-CaP formation. The apatite-forming process was tested in simulated body fluid (SBF). The results demonstrated that the incorporation of Mg2+ and/or CO32- ions enabled the L-CaP to cover the entire surface of Zr-50Ti alloys within only one day. After short-term soaking in SBF, the L-CaP layer, modulated by Mg2+ and/or CO32- ions, formed a uniform hydroxyapatite (HA) coating on the surface of the Zr-50Ti alloys, showing potential for optimized bone integration. After soaking in SBF for 14 days, the bonding strength between the apatite layer and alloy has the potential to meet the orthopedic application requirement of 22 MPa. This study demonstrates an effective method to enhance the bioactivity and bonding strength of Zr-50Ti alloys for orthopedic applications.

Calcium Citrate Amount and Gelatine Source Impact on Hydroxyapatite Formation in Bone Regeneration Material in Simulated Body Fluid.

Bone grafting is crucial for bone regeneration. Recent studies have proposed the use of calcium citrate (CC) as a potential graft material. Notably, citrate does not inhibit hydroxyapatite (HAp) formation at specific calcium-to-citrate molar ratios. Octacalcium phosphate (OCP)/gelatine (Gel) composites, which are commonly produced from porcine Gel, are valued for their biodegradability and bone replacement capability. This study introduces fish Gel as an alternative to porcine Gel because of its wide acceptance and eco-friendliness. This is the first study to examine the interaction effects between two osteogenic materials, OCP/CC, and the influence of different gelatine matrix components on HAp formation in an SBF. Samples with varying CC contents were immersed in an SBF for 7 d and analysed using various techniques, confirming that high CC doses prevent HAp formation, whereas lower doses facilitate it. Notably, small-sized OCP/CC/porcine Gel composites exhibit a high HAp generation rate. Porcine Gel composites form denser HAp clusters, whereas fish Gel composites form larger spherical HAps. This suggests that lower CC doses not only avoid inhibiting HAp formation but also enhance it with the OCP/Gel composite. Compared with porcine Gel, fish Gel composites show less nucleation but an increased crystal growth for HAp.

Development of new generation cakes fortified with zinc oxide nanoparticles.

This study aimed to develop new generation cakes that were fortified with calcined ZnO nanoparticles (CZnO), uncalcined ZnO nanoparticles (UCZnO), beads (B(CZnO)) synthesized by encapsulating the CZnO with sodium alginate (SA), and the beads (B(UCZnO)) synthesized by encapsulating the UCZnO with sodium alginate (SA) and investigated the zinc (Zn) release in fortified cakes in simulated body fluids (SBF). The present study represents a novel method for increasing intestinal absorption and bioavailability of dietary zinc with zinc nanoparticles for use in the preparation of Zn fortified cakes as a dietary supplement to compensate for zinc deficiency in humans. The results revealed that a rapid increase in the release time and rate in the SGF solution was noted in the UCZnO added cakes. It was attributed to increased intestinal absorption and bioavailability as a result of the ultra-small size of ZnO. Also, ZnO release kinetics in SBF was also studied and data were adjusted into different kinetic models involving zero-order, first-order, Higuchi, and Korsmeyer-Peppas models. The present investigation recommends adding UCZnO to the cakes to control and increase the release from the cakes. Supplementary Information: The online version contains supplementary material available at 10.1007/s13197-023-05840-x.

Effects of Argon Gas Plasma Treatment on Biocompatibility of Nanostructured Titanium.

In this study, we applied argon plasma treatment to titanium surfaces with nanostructures deposited by concentrated alkali treatment and investigated the effects on the surface of the material and the tissue surrounding an implant site. The results showed that the treatment with argon plasma removed carbon contaminants and increased the surface energy of the material while the nanoscale network structure deposited on the titanium surface remained in place. Reactive oxygen species reduced the oxidative stress of bone marrow cells on the treated titanium surface, creating a favorable environment for cell proliferation. Good results were observed in vitro evaluations using rat bone marrow cells. The group treated with argon plasma exhibited the highest apatite formation in experiments using simulated body fluids. The results of in vivo evaluation using rat femurs revealed that the treatment improved the amount of new bone formation around an implant. Thus, the results demonstrate that argon plasma treatment enhances the ability of nanostructured titanium surfaces to induce hard tissue differentiation and supports new bone formation around an implant site.

Nickel ion release and surface analyses on instrument fragments fractured beyond the apex: a laboratory investigation.

BACKGROUND: To analyse the changes in surface and nickel ion release characteristics of fractured root canal shaping instruments in a simulated body fluid environment. METHODS: A total of 54 new instruments were studied. The instrument groups consisted of five different NiTi alloys and a stainless-steel alloy. To standardize instrument fracture, a torsional type of failure was created on each instrument. The fractured specimens of each instrument group were randomly divided into three static immersion subgroups of 1 h, 7-day, and 30-day (n = 3). Simulated body fluid (SBF) was prepared to mimic human blood plasma by Kokubo&Takadama protocol for ex situ static immersions at 37ºC. The surfaces were examined via scanning electron microscopy coupled with energy-dispersive X-ray spectroscopy. To determine the quantitative ion release, the retrieved SBFs were analyzed using inductively coupled plasma mass spectrometry. Two-way ANOVA and Tukey post hoc tests sought the statistical significance of the nickel ion values(p < 0.05). RESULTS: In 1 h of immersion, the newly formed structures, exhibiting mostly oxygen signals, were widespread and evident on NiTi surfaces. In contrast, fewer structures were detected on the SS surface in that subgroup. In 7 days of immersion, a tendency for a decrease in the density of the new structures was revealed in NiTi groups. The oxygen signals on NiTi group surfaces significantly increased, contrary to their decrease in SS. Signals of sodium, chlorine, and calcium were detected, indicating salt precipitates in groups. In 30 days of immersion, salt precipitates continued to form. The Ni-ion release values in all instrument groups presented significant differences in comparison to the SBF control in all immersion periods(p < 0.001). No significant differences were observed in immersion time periods or instrument groups(p > 0.05). CONCLUSIONS: Within the limitations of the presented study, it was concluded that the fractured SS and NiTi root canal instruments release Ni ions in contact with body fluid. However, the Ni ion release values determined during the observation periods are lower than the critical toxic or allergic thresholds defined for the human body. This was due to the ionic dissolution cycle reaching a stable state from 1-hour to 30-day exposure to the body fluid of fractured instruments.

Transformation behaviour of salts composed of calcium ions and phosphate esters with different linear alkyl chain structures in a simulated body fluid modified with alkaline phosphatase.

Ceramic biomaterials have been used for the treatment of bone defects and have stimulated intense research on such materials. We have previously reported that a salt composed of calcium ions and a phosphate ester (SCPE) transformed into hydroxyapatite (HAp) in a simulated body fluid (SBF) modified with alkaline phosphatase (ALP), and proposed SCPEs as a new category of ceramic biomaterials, namely bioresponsive ceramics. However, the factors that affect the transformation of SCPEs to HAp in the SBF remained unclear. Therefore, in this study, we investigated the behaviour of calcium salts of methyl phosphate (CaMeP), ethyl phosphate (CaEtP), butyl phosphate (CaBuP), and dodecyl phosphate (CaDoP) in SBF with and without ALP modification. For the standard SBF, an X-ray diffraction (XRD) analysis indicated that these SCPEs did not readily transform into calcium phosphate. However, CaMeP, CaEtP, and CaBuP were transformed into HAp and octacalcium phosphate in the SBF modified with ALP; therefore, these SCPEs can be categorised as bioresponsive ceramics. Although CaDoP did not exhibit a sufficient response to ALP to be detected by XRD, it is likely to be a bioresponsive ceramic based on the results of morphological observations. The transformation rate for the SCPEs decreased with increasing size of the linear alkyl group of the phosphate esters. The rate-determining steps for the transformation reaction of the SCPEs were changed from the dissolution of the SCPEs to the hydrolysis of the phosphate esters with increasing size of the phosphate ester alkyl groups. These findings contribute to designing novel bioresponsive ceramic biomaterials.

Mixed oxide nanotubes in nanomedicine: A dead-end or a bridge to the future?

Nanomedicine has seen a significant rise in the development of new research tools and clinically functional devices. In this regard, significant advances and new commercial applications are expected in the pharmaceutical and orthopedic industries. For advanced orthopedic implant technologies, appropriate nanoscale surface modifications are highly effective strategies and are widely studied in the literature for improving implant performance. It is well-established that implants with nanotubular surfaces show a drastic improvement in new bone creation and gene expression compared to implants without nanotopography. Nevertheless, the scientific and clinical understanding of mixed oxide nanotubes (MONs) and their potential applications, especially in biomedical applications are still in the early stages of development. This review aims to establish a credible platform for the current and future roles of MONs in nanomedicine, particularly in advanced orthopedic implants. We first introduce the concept of MONs and then discuss the preparation strategies. This is followed by a review of the recent advancement of MONs in biomedical applications, including mineralization abilities, biocompatibility, antibacterial activity, cell culture, and animal testing, as well as clinical possibilities. To conclude, we propose that the combination of nanotubular surface modification with incorporating sensor allows clinicians to precisely record patient data as a critical contributor to evidence-based medicine.

Surface-Activated Fibre-Like SBA-15 as Drug Carriers for Bone Diseases.

Here, we report an inorganic hexagonally ordered mesoporous fibre-like carrier made of silica as an effective drug delivery system with mineralisation potential. Fibre-like SBA-15 has been modified by employing a simple surface activation (rehydroxylation) procedure. The surface-rehydroxylated fibre-like SBA-15 (SBA-15-R) was used to investigate the possible mechanism of hydroxyapatite (HA) nucleation and deposition onto silica's surface after immersion in simulated body fluid (SBF). Amorphous calcium phosphate, Ca-deficient HA and bone-like HA deposits were observed on SBA-15-R surface consecutively after 7, 14 and 21 days of immersion in SBF. Accordingly, our low-angle XRD, STEM and N2 adsorption/desorption results indicated that deposited ions were mostly located at the silica's surface and could modify the size of the mesopores. The SBA-15-R was studied in vitro as the potential bioactive drug delivery system using doxorubicin (DOX) as a model water-soluble and anticancer drug. The adsorbed DOX molecules were mostly located at the pore walls and pore openings, likely together with the silanol groups. The DOX release was diffusion-controlled and relatively slower in SBF (pH = 7.4) than in phosphate-buffered solution (pH = 5.0), most probably due to both the stronger electrostatic interactions occurring between the DOX and the SBA-15-R and the simultaneous deposition of calcium and phosphates ions from SBF.

Long-term sealing ability of 3 endodontic obturation techniques.

This in vitro study sought to evaluate the sealing ability of 3 root canal obturator systems after immersion in simulated body fluid for 1 year. The coronal sections of 30 single-rooted teeth were removed at the cementoenamel junction at 12 mm (±1 mm), and roots were instrumented with nickel titanium instruments. Specimens were divided into 3 groups (n = 10) according to the obturation manufacturer-specified system and immersed in simulated body fluid. A digital fluid flow-meter was used to detect the flow rate at 1 week, 1 month, and 12 months after immersion. This study demonstrated that the tested endodontic obturation systems were unable to keep their sealing ability stable during the first year. At 12 months, all root filling systems showed increased flow rates (P < 0.0001).

Modified five times simulated body fluid for efficient biomimetic mineralization.

Simulated body fluid (SBF) is widely utilized in preclinical research for estimating the mineralization efficacy of biomaterials. Therefore, it is of great significance to construct an efficient and stable SBF mineralization system. The conventional SBF solutions cannot maintain a stable pH value and are prone to precipitate homogeneous calcium salts at the early stages of the biomimetic process because of the release of gaseous CO2. In this study, a simple but efficient five times SBF buffered by 5 % CO2 was developed and demonstrated to achieve excellent mineralized microstructure on a type of polymer-aligned nanofibrous scaffolds, which is strikingly similar to the natural human bone tissue. Scanning electron microscopy and energy-dispersive X-ray examinations indicated the growth of heterogeneous apatite with a high-calcium-to-phosphate ratio on the aligned nanofibers under 5 times SBF buffered by 5 % CO2. Moreover, X-ray diffraction spectroscopy and Fourier transform infrared analyses yielded peaks associated with carbonated hydroxyapatite with less prominent crystallization. In addition, the biomineralized aligned polycaprolactone nanofibers demonstrated excellent cell attachment, alignment, and proliferation characteristics in vitro. Overall, the results of this study showed that 5 × SBFs buffered by 5 % CO2 partial pressure are attractive alternatives for the efficient biomineralization of scaffolds in bone tissue engineering, and could be used as a model for the prediction of the bone-bonding bioactivity of biomaterials.

Decomposition of Luminescent Hydroxyapatite Scaffolds in Simulated Body Fluid.

We present a luminescence study investigating the dissolution of rare-earth-doped hydroxyapatite scaffolds in simulated body fluid (SBF), aiming to assess the luminescence stability of Tb-, Ce-, and Eu-doped scaffolds over time. Our findings reveal a consistent decrease in luminescence emission intensity across all samples over a four-week period in which the scaffolds were immersed in the SBF. In addition, energy-dispersive spectroscopy confirms a decrease in rare-earth ion concentration in the scaffolds with respect to time, whereas fluorescence spectroscopy shows the presence of rare-earth ions in the SBF, indicating the partial dissolution of the scaffolds over time. The use of rare-earth ions as luminescence markers provides insights into the mechanisms of apatite formation in hydroxyapatites. Thus, these scaffolds may find wider use in regenerative medicine, particularly in targeted drug delivery systems, where their luminescent properties have the potential to noninvasively track drug release.

Mineralized Biopolymers-Based Scaffold Encapsulating with Dual Drugs for Alveolar Ridge Preservation.

Mineralization of scaffolds is essential for alveolar ridge preservation and bone tissue engineering, enhancing the mechanical strength and bioactivity of scaffolds, and promoting better integration with natural bone tissue. While the in situ mineralization method using concentrated SBF solutions is promising, there is limited comprehensive research on its effects. In this study, it is demonstrate that soaking gelatin/alginate scaffolds (GAS) in fivefold concentrated SBF significantly reduces the mineralization time to 3-7 days but also leads to considerable degradation and loss of the scaffold's original microstructure. The ratio of gelatin to alginate is optimized to improve the properties of GAS. The optimized GAS sample, when soaked in concentrated SBF to form GAS/HAp, exhibited hydroxyapatite (HAp) crystal formation starting from day 3, with mature hexagonal crystals forming by day 7. However, this process also caused significant decomposition and deformation of the scaffold's pore structure. Additionally, the biocompatibility of GAS and GAS/HAp is evaluated through in vitro, in ovo, haemolysis, and anti-ROS assays. The findings highlight the impact of SBF5× on the mineralization of GAS, laying the groundwork for further research in alveolar ridge preservation and bone tissue engineering.

Influence of polylactide coating stereochemistry on mechanical and in vitro degradation properties of porous bioactive glass scaffolds for bone regeneration.

The mechanical properties of polylactide stereocomplexes (PLA SC) have been primarily studied through tensile testing, with inconsistent results, and the compressive properties of PLA SC compared to homocrystalline or amorphous PLA remain poorly understood. In this study, we coated porous bioactive glass 13-93 scaffolds with amorphous, homocrystalline, or stereocomplex PLA to investigate their mechanical and degradation properties before and after immersion in simulated body fluid. The glass scaffolds had interconnected pores and an average porosity of 76%. The PLA coatings, which were 10-100 µm thick and approximately 3% of the glass scaffold mass, covered the glass to a large extent. The compressive strength and toughness of all PLA-coated scaffolds were significantly higher than those of uncoated scaffolds, with approximately a fourfold increase before immersion and a twofold increase after immersion. The compressive strength and toughness of PLA SC-coated scaffolds were similar to those of scaffolds with homocrystalline PLA coating, and significantly higher than for scaffolds with amorphous PLA coating. All PLA coatings moderated the initial pH increase caused by the glass, which could benefit surrounding cells and bone tissue in vivo after implantation.

Microstructure, Mechanical Properties and Corrosion Performance of Laser-Welded NiTi Shape Memory Alloy in Simulated Body Fluid.

Laser-welding is a promising technique for welding NiTi shape memory alloys with acceptable tensile strength and comparable corrosion performance for biomedical applications. The microstructural characteristics and localized corrosion behavior of NiTi alloys in a simulated body fluid (SBF) environment are evaluated. A microstructural examination indicated the presence of fine and equiaxed grains with a B2 austenite phase in the base metal (BM), while the weld metal (WM) had a coarse dendritic microstructure with intermetallic precipitates including Ti2Ni and Ni4Ti3. The hardness decreased from the BM to the WM, and the average hardness for the BM was 352 ± 5 HV, while it ranged between 275 and 307 HV and 265 and 287 HV for the HAZ and WM, respectively. Uni-axial tensile tests revealed a substantial decrease in the tensile strength of NiTi WM (481 ± 19 MPa), with a reduced joint efficiency of 34%. The localized corrosion performance of NiTi BM was superior to the WM, with electrochemical test responses indicating a pitting potential and low corrosion rate in SBF environments. The corrosion rate of the NiTi BM and WM was 0.048 ± 0.0018 mils per year (mpy) and 0.41 ± 0.019 mpy, respectively. During welding, NiTi's strength and biocompatibility properties changed due to the alteration in microstructure and formation of intermetallic phases as a result of Ti enrichment. The performance and safety of welded medical devices may be impacted during welding, and it is essential to preserve the biocompatibility of NiTi components for biomedical applications.

Micro and nano plastics release from a single absorbable suture into simulated body fluid.

Synthetic polymers are widely used in medical devices and implants where biocompatibility and mechanical strength are key enablers of emerging technologies. One concern that has not been widely studied is the potential of their microplastics (MPs) release. Here we studied the levels of MP debris released following 8-week in vitro tests on three typical polyglycolic acid (PGA) based absorbable sutures (PGA 100, PGA 90 and PGA 75) and two nonabsorbable sutures (polypropylene-PP and polyamide-PA) in simulated body fluid. The MP release levels ranked from PGA 100 > > PGA 90 > PGA 75 > > PP ∼ PA. A typical PGA 100 suture released 0.63 ± 0.087 million micro (MPs > 1 µm) and 1.96 ± 0.04 million nano (NPs, 200-1000 nm) plastic particles per centimeter. In contrast, no MPs were released from the nonabsorbable sutures under the same conditions. PGA that was co-blended with 10-25% L-lactide or epsilon-caprolactone resulted in a two orders of magnitude lower level of MP release. These results underscore the need to assess the release of nano- and microplastics from medical polymers while applied in the human body and to evaluate possible risks to human health.

PMMA bone cement with L-arginine/nano fish bone nanocomplex for apatite formation.

Bone cement is one of the materials used in orthopaedics that serves various functions, such as binding bone implants, replacing damaged bones and filling spaces within bones. Various materials have been used to synthesize bone cement, and one promising material for further research is fish bone waste-based bone cement. This study investigates the potential of fish bone waste-based bone cement by incorporating nano fish bone (NFB) and L-arginine (L-Arg) protein into polymethyl methacrylate (PMMA) to examine apatite growth. NFB derived from the Salmo salar fish positively influences osteoblast cell proliferation and differentiation, while L-Arg enhances biocompatibility and antibiotic properties. The NFB/L-Arg combination holds promise in accelerating new bone formation and cell growth, both of which are crucial for fracture healing and bone remodelling. Tensile strength tests reveal the superior performance of BC-PMMA-1-NFB/L-Arg (36.11 MPa) compared with commercial PMMA (32 MPa). Immersion tests with simulated body fluid (SBF) solution for 7 days reveal accelerated apatite layer formation, emphasizing the potential benefits of NFB/L-Arg in bone cement applications.

Thermodynamic and Kinetic Studies of the Precipitation of Double-Doped Amorphous Calcium Phosphate and Its Behaviour in Artificial Saliva.

Simulated body fluid (SBF) and artificial saliva (AS) are used in biomedical and dental research to mimic the physiological conditions of the human body. In this study, the biomimetic precipitation of double-doped amorphous calcium phosphate in SBF and AS are compared by thermodynamic modelling of chemical equilibrium in the SBF/AS-CaCl2-MgCl2-ZnCl2-K2HPO4-H2O and SBF/AS-CaCl2-MgCl2-ZnCl2-K2HPO4-Glycine/Valine-H2O systems. The saturation indices (SIs) of possible precipitate solid phases at pH 6.5, close to pH of AS, pH 7.5, close to pH of SBF, and pH 8.5, chosen by us based on our previous experimental data, were calculated. The results show possible precipitation of the same salts with almost equal SIs in the two biomimetic environments at the studied pHs. A decrease in the saturation indices of magnesium and zinc phosphates in the presence of glycine is a prerequisite for reducing their concentrations in the precipitates. Experimental studies confirmed the thermodynamic predictions. Only X-ray amorphous calcium phosphate with incorporated Mg (5.86-8.85 mol%) and Zn (0.71-2.84 mol%) was obtained in the experimental studies, irrespective of biomimetic media and synthesis route. Solid-state nuclear magnetic resonance (NMR) analysis showed that the synthesis route affects the degree of structural disorder of the precipitates. The lowest concentration of dopant ions was obtained in the presence of glycine. Further, the behaviour of the selected amorphous phase in artificial saliva was studied. The dynamic of Ca2+, Mg2+, and Zn2+ ions between the solid and liquid phases was monitored. Both direct excitation 31P NMR spectra and 1H-31P CP-MAS spectra proved the increase in the nanocrystalline hydroxyapatite phase upon increasing the incubation time in AS, which is more pronounced in samples with lower additives. The effect of the initial concentration of doped ions on the solid phase transformation was assessed by solid-state NMR.

Apatite Formation on α-Tricalcium Phosphate Modified with Bioresponsive Ceramics in Simulated Body Fluid Containing Alkaline Phosphatase.

Bioresponsive ceramics, a new concept in ceramic biomaterials, respond to biological molecules or environments, as exemplified by salts composed of calcium ions and phosphate esters (SCPEs). SCPEs have been shown to form apatite in simulated body fluid (SBF) containing alkaline phosphatase (ALP). Thus, surface modification with SCPEs is expected to improve the apatite-forming ability of a material. In this study, we modified the surface of α-tricalcium phosphate (α-TCP) using methyl, butyl, or dodecyl phosphate to form SCPEs and investigated their apatite formation in SBF and SBF containing ALP. Although apatite did not form on the surface of the unmodified α-TCP in SBF, apatite formation was observed following surface modification with methyl or butyl phosphate. When ALP was present in SBF, apatite formation was especially remarkable on α-TCP modified with butyl phosphate. These SCPEs accelerated apatite formation by releasing calcium ions through dissolution and supplying inorganic phosphate ions, with the latter process only occurring in SBF containing ALP. Notably, no apatite formation occurred on α-TCP modified with dodecyl phosphate, likely because of the low solubility of the resulting calcium dodecyl phosphate/calcium phosphate composites. This new method of using SCPEs is anticipated to contribute to the development of novel ceramic biomaterials.

Structure and magnetic properties of SiO2-FeO-CaO-Na2O bioactive glass-ceramic system for magnetic fluid hyperthermia application.

Ferrimagnetic glass-ceramics comprising maghemite crystals were synthesized for magnetic fluid hyperthermia (MFH) usage. The present work is focused on the result of the chemical composition and heat treatment temperature on the magnetic behavior of (60-x)SiO2-(10+x)FeO-20CaO-10Na2O,0≤x≤30 glass-ceramic system. It was observed that with the increasing of FeO from 10 to 40 wt% in the glass-ceramic compound, the percentage of maghemite phase increased. It was also seen that in the low heat treatment temperature (680 °C), by adding iron oxide up to 30 wt%, iron cations acts as a network former, and more than this amount acts as a network modifier. In contrast, iron cations in the same composition range at high temperatures (840 °C), acts as a network modifier. According to the VSM results, the maximum magnetization of glass-ceramics incremented from 0.23 emu/g to 0.30 emu/g with the increase in FeO percentage. It was also observed that with the increment of iron oxide percentage, the morphology of maghemite crystals changed from spherical to dumbbell-shaped.

Fatigue behavior of biodegradable Zn-Li binary alloys in air and simulated body fluid with pure Zn as control.

Zn-Li-based alloys have drawn great attention as promising candidates for load-bearing sites, such as intramedullary nails and bone plates. They possess high monotonic strength (over 500MPa) and better pitting resistance with lithium-rich layers acting as barriers for corrosion attack under (quasi-)static conditions. However, their response to dynamic loadings such as fatigue is still unknown. Herein, the corrosion fatigue behavior of a series of Zn-Li binary alloys with different lithium addition amounts was tested in simulated body fluid. Tensile and fatigue strength of the materials were proportional to lithium content while corrosion fatigue strength was not. Extremely long cracks that extended parallel to the loading direction were found in Zn-1.0wt.%Li alloys. These cracks propagated by selective dissolution of the lithium-rich phase in the eutectoid regions and drastically reduced the corrosion fatigue strength of Zn-1.0wt.%Li alloy owing to exacerbated crack propagation. To sum up, Zn-Li binary alloys showed fatigue strength comparable to pure iron and pure titanium, which confirmed their loading capacity under dynamic conditions. STATEMENT OF SIGNIFICANCE: Zn-Li-based alloys are qualified as biodegradable metals and are dedicated to load-bearing applications. Current research has shown that lithium can suppress pitting corrosion by the formation of lithium-rich layers on the alloy surface during (quasi-)static conditions. However, how these materials respond to dynamic loading is still unknown. The present study investigated the influence of lithium amount (0.1∼1.0wt.%) on the corrosion fatigue behavior of binary Zn-Li alloys. The results showed that lithium effectively improved the mechanical strength but can harm corrosion fatigue strength at high content due to selective dissolution of lithium-rich phase. This demonstrated that the amount of lithium should be controlled for optimal properties. Zn-0.8wt.%Li alloy demonstrated a good combination of tensile and corrosion fatigue strength, which can be further improved by proper alloying and thermomechanical treatment.