Simulated Body Environment Research Articles

An investigation regarding semiconducting and passive behaviors of coarse- and nano-structured pure Ta in Ringer’s physiological electrolyte: role of anodic passive potential

Through this survey, by the application of magnetron sputtering technique, an unprecedented nano-structured (NS) α-Ta was coated on Ti substrate. The provided coating was fully dens, homogeneous in microstructure and with crystals preferable to specific plane of (110). Employing comprehensive electrochemical evaluations, the formed passive layer on the α-Ta coating and pure uncoated Ta in the Ringer’s electrolyte at 37 °C were compared in various aspects including the electrochemical response, semiconductivity, donor density (ND) and the point defects diffusivity (D0). The α-Ta coated sample showed much higher corrosion resistance in Ringer’s electrolyte than the bare Ta. Moreover, Mott–Schottky analysis revealed a reduced ND in the passive layer formed on the α-Ta coating compared to that of the pure Ta. The calculated quantities of D0 for the α-Ta coating (1.06 × 10−17 cm2 s−1) are more than values of the pure Ta (0.94 × 10−17 cm2 s−1). The enhanced corrosion resistant behavior of α-Ta coating in the simulated body environment, compared to the pure Ta specimen, can be attributed to the formation of nano-scale microstructure and the crystallographic texture in the coated sample that accelerates the formation of a sturdy and ameliorated passive film with denser structure.

Structural Effects of Sulfur-Containing Functional Groups on Apatite Formation on Ca2+-Modified Copolymers in a Simulated Body Environment.

Chemical modification with specific functional groups has been the conventional method to develop bone-bonding bioactive organic–inorganic hybrids. These materials are attractive as bone substitutes because they are flexible and have a Young’s modulus similar to natural bone. Immobilization of sulfonic acid groups (−SO3H) onto the polymer chain is expected to produce such hybrids because these groups induce apatite formation in a simulated body fluid (SBF) and enhance the activity of osteoblast-like cells. Sulfinic acid groups (−SO2H), which are derivatives of −SO3H, can also induce apatite nucleation. However, the structural effects of such sulfur-containing functional groups on apatite formation have not been elucidated. In the present study, apatite formation on Ca2+-modified copolymers containing −SO2H or −SO3H was investigated in a simulated body environment. The copolymer containing Ca2+ and −SO3H promoted Ca2+ release into the SBF and formed apatite faster (1 day) than the copolymer containing Ca2+ and −SO2H (14 days). In contrast, when they were not modified with Ca2+, the copolymer containing only −SO2H deposited the apatite faster (7 days) than that containing only −SO3H (>7 days) in the solution with Ca2+ concentration 1.5 times that of SBF. The former adsorbed larger amounts of Ca2+ than the latter. The measured stability constant of the complex indicated that the interaction of −SO2–···Ca2+ was more stable than that of −SO3–···Ca2+. It was found that both the release and adsorption of Ca2+ governed by the stability played an important role in induction of the apatite formation and that the apatite-forming ability of sulfur-containing functional groups drastically changed by the coexistence of Ca2+.

Mechanical properties and bio-tribological behaviors of novel beta-Zr-type Zr-Al-Fe-Nb alloys for biomedical applications

The present study prepares novel Zr70+xAl5Fe15−xNb10 (x=0, 5) alloys by arc-melting for potential biomedical application. The mechanical properties and bio-tribological behaviors of the Zr-based alloys are evaluated and compared with biomedical pure Zr. The as-prepared alloys exhibit a microstructure containing a micrometer-sized dendritic beta-Zr phase dispersed in a Zr2Fe-typed matrix. It is found that increasing the content of Zr is favorable for the mechanical compatibility with a combination of low Young's modulus, large plasticity, and high compressive strength. The wear resistance of the Zr-Al-Fe-Nb alloys in air and phosphate buffer saline (PBS) solution is superior to that of pure Zr. The wear mechanism of Zr-based alloys sliding in air is controlled by oxidation and abrasive wear whereas that sliding in PBS is controlled by synergistic effects of the abrasive and corrosive wear. Electrochemical measurements demonstrate that the Zr-based alloys are corrosion resistant in PBS. Their bio-corrosion resistance is improved with the increase in Zr content, which is attributed to the enrichment in Zr and decrease in Al concentration in the surface passive film of alloys. The Zr75Al5Fe10Nb10 exhibits the best corrosion resistance in PBS, which contributes to its superior wear resistance in a simulated body environment. The combination of good mechanical properties, corrosion resistance, and biotribological behaviors of the Zr-Al-Fe-Nb alloys offers them potential advantages in biomedical applications.

Polarization characteristics of rolled AZ31 magnesium alloy in simulated body environment

Polarization characteristics of rolled AZ31 magnesium alloy in simulated body environment

Fabrication of thick nanoporous oxide films on stainless steel via DC anodization and subsequent biofunctionalization

Abstract Remarkably thick nanoporous anodic films have been formed through simple DC anodization by adding hydrogen peroxide as an oxidant to a sulfuric acid electrolyte. This result was not possible when using the previously reported pulsed polarization technique. While this anodic film's growth was significantly promoted by DC anodization, having only sulfuric acid resulted in the preferential anodic dissolution of the substrate material. Transmission electron microscopy of the anodic film's cross-section confirmed that the film has numerous fine pores with a size distribution ranging from 5 nm to 20 nm. Energy-dispersive x-ray spectroscopic analysis of the anodized specimens revealed that the films were composed of a complex chromium-rich oxide. In addition, coating stainless steel with thick nanoporous oxide films through anodization in the optimized conditions confirmed that it could act as a highly suitable host for synthetic hydroxyapatite coating, resulting in the enhanced growth of natural apatite in a simulated body environment. The enhancement of the apatite deposition is attributed to the availability of the empty pore volume in the thick anodic porous films, formed on stainless steel surfaces. These findings suggest a novel functionality to stainless-steel surface modification.

Investigation of dual phase (β+γ) CoNiAl MSMA Micro structure effect on the Mechanical Properties and Bio-Corrosion Resistance

In this study five compositions of CoNiAl alloy with fixed Al content were prepaid to investigate the effect of chemical composition on the microstructure and phase volume fractions. It was found that by increasing Co the volume fraction of β phase increases and by increasing the β phase the grain size will be increased. This increase will be reflected on increasing the hardness of this alloy. Further investigations for the corrosion resistance in simulated body environment were done. It was found that phase volume fractions increased corrosion rate by increasing the volume fraction of β phase.

Controllable degradation of medical magnesium by electrodeposited composite films of mussel adhesive protein (Mefp-1) and chitosan

To control the degradation rate of medical magnesium in body fluid environment, biocompatible films composed of Mussel Adhesive Protein (Mefp-1) and chitosan were electrodeposited on magnesium surface in cathodic constant current mode. The compositions and structures of the films were characterized by atomic force microscope (AFM), scanning electron microscope (SEM) and infrared reflection absorption spectroscopy (IRAS). And the corrosion protection performance was investigated using electrochemical measurements and immersion tests in simulated body fluid (Hanks’ solution). The results revealed that Mefp-1 and chitosan successfully adhered on the magnesium surface and formed a protective film. Compared with either single Mefp-1 or single chitosan film, the composite film of chitosan/Mefp-1/chitosan (CPC (chitosan/Mefp-1/chitosan)) exhibited lower corrosion current density, higher polarization resistance and more homogenous corrosion morphology and thus was able to effectively control the degradation rate of magnesium in simulated body environment. In addition, the active attachment and spreading of MC3T3-E1 cells on the CPC film coated magnesium indicated that the CPC film was significantly able to improve the biocompatibility of the medical magnesium.

Effects of the Dynamic Tapping Process on the Biocompatibility of Ti-6Al-4V Alloy in Simulated Human Body Environment

The use of biomaterials depends on the high quality of the manufacturing and processing technology. Thus, the goal of this study is to contribute to the field of manufacturing of biomedical devices used in the human body. The forming and machining microtapping process (M3 thread and pitch 0.5 mm) in Ti-6Al-4V alloy was investigated. The design of experiments (DoE) was performed to identify the effects of factors (speed and type of process) on the thrust force, torque, and ultra-microhardness. The biocompatibility of the formed and machined thread surfaces was evaluated through potentiostatic polarization and electrochemical impedance tests. A simulated body fluid was used as the electrolyte. The experimental results showed that the rate of passivation of titanium alloy was highest for machined threads. Furthermore, the low level of speed (2 m/min) presented better surface finish and more complete fill rate of thread profile.

Co-encapsulation of tamoxifen citrate and quercetin using 2HP-β-cyclodextrin: a response surface experimental design

The aim of this study is to prepare a nanosphere containing the insoluble anti-cancer drug called tamoxifen citrate. The synthesized nanosphere is composed of tamoxifen citrate (TMC), 2-hydroxy propyl-β-cyclodextrin (2HP-β-CD), quercetin (QT) and polycaprolactone (PCL), which was prepared using water in oil in water emulsion solvent extraction method. 2HP-β-CD and QT were applied to enhance the solubility and bioavailability of the drug, respectively. The response surface method was used to optimize the operating variables such as PCL polymer mass, stabilizer percentage, continuous water volume and ratio based on the central composite design. Quadratic models were developed for two responses: the drug encapsulation efficiency and the nanosphere size. According to the results, the optimum conditions to achieve a nanosphere of a small size and high drug entrapment efficiency included 30 mg PCL, 2% (w/v) PVA stabilizer, 80 ml water and equivalent ratio of 0.5. According to the UV analysis based on the second derivative spectrophotometric technique, the estimated encapsulation efficiency of TMC was 53% ± 2. Scanning electron microscopy (SEM) showed that the mean particle size of the synthesized nanospheres was 205 nm, which is appropriate for oral usage. In addition, the in vitro release of TMC and QT in the simulated body environment (SGF and SIF) was performed at 37 °C. The in vitro release of TMC at pH = 7.4 showed that TMC and QT had a slow and simultaneous release behaviour. This confirms the controllable release of TMC in the new synthesized nanoparticle form.

擬似生体環境下でのポリ乳酸の分解の評価

擬似生体環境下でのポリ乳酸の分解の評価

Effect of shot peening on the corrosive resistance of Ti-alloy under simulated body environment

Effect of shot peening on the corrosive resistance of Ti-alloy under simulated body environment

Degradation of Ti–6Al–4V alloy under cyclic loading in a simulated body environment with cell culturing

The present study reports the corrosion fatigue of the Ti–6Al–4V alloy using cyclic deformation test in a simulated body fluid under cell culturing for the first time. Cyclic deformation tests were carried out using three types of specimens to reveal the effects of proteins and cells on the corrosion fatigue of the alloy. For the 1-day-immersed and 1-week-immersed specimens, tensile specimens were soaked in a simulated body fluid for 1 day and 1 week, respectively, before cyclic deformation test, whereas for the cell-cultured specimen, MC3T3-E1 osteoblast-like cells were seeded and then cultured on tensile specimens for 1 week. The incubation period for crack initiation was longer for the cell-cultured and 1-week-immersed specimens compared to that for the 1-day-immersed specimen. On the other hand, crack propagation period for the cell-cultured and 1-week-immersed specimens was shorter than that for the 1-day-immersed specimen. These results indicate that proteins and cells adhered on the alloy surface inhibit metal dissolution at newly created surface emerged by cyclic deformation to suppress crack initiation, whereas they accelerate crack propagation because dissolution at crack tip is accelerated in the occluded space formed under proteins and cells.

A Zr-based bulk metallic glass for future stent applications: Materials properties, finite element modeling, and in vitro human vascular cell response

Despite the prevalent use of crystalline alloys in current vascular stent technology, new biomaterials are being actively sought after to improve stent performance. In this study, we demonstrated the potential of a Zr–Al–Fe–Cu bulk metallic glass (BMG) to serve as a candidate stent material. The mechanical properties of the Zr-based BMG, determined under both static and cyclic loadings, were characterized by high strength, which would allow for the design of thinner stent struts to improve stent biocompatibility. Finite element analysis further complemented the experimental results and revealed that a stent made of the Zr-based BMG was more compliant with the beats of a blood vessel, compared with medical 316L stainless steel. The Zr-based BMG was found to be corrosion resistant in a simulated body environment, owing to the presence of a highly stable ZrO2-rich surface passive film. Application-specific biocompatibility studies were conducted using human aortic endothelial cells and smooth muscle cells. The Zr–Al–Fe–Cu BMG was found to support stronger adhesion and faster coverage of endothelial cells and slower growth of smooth muscle cells than 316L stainless steel. These results suggest that the Zr-based BMG could promote re-endothelialization and potentially lower the risk of restenosis, which are critical to improve vascular stent implantation integration. In general, findings in this study raised the curtain for the potential application of BMGs as future candidates for stent applications. Statement of SignificanceVascular stents are medical devices typically used to restore the lumen of narrowed or clogged blood vessel. Despite the clinical success of metallic materials in stent-assisted angioplasty, post-surgery complications persist due to the mechanical failures, corrosion, and in-stent restenosis of current stents. To overcome these hurdles, strategies including new designs and surface functionalization have been exercised. In addition, the development of new materials with higher performance and biocompatibility can intrinsically reduce stent failure rates. The present study demonstrates the advantages of a novel material, named bulk metallic glass (BMG), over the benchmarked 316L stainless steel through experimental methods and computational simulations. It raises the curtain of new research endeavors on BMGs as competitive alternatives for stent applications.

Dimensional Changes, Microstructure, Microhardness Distributions And Corrosion Properties Of Iron And Iron-Manganese Sintered Materials

Abstract Iron samples and Fe-Mn alloys with Mn content of 25 wt.% and 30 wt.% were prepared by blending, compressing and sintering with the aim to study their dimensional changes, microstructure, microhardness distribution and primarily the electrochemical corrosion behaviour in a simulated body environment. The light microscopy (LM), scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDX) and micro-hardness measurements revealed a microheterogeneous multiphase structure of sintered Fe-Mn samples. The potentiodynamic tests have demonstrated that the corrosion rates of such Fe-Mn alloys immersed in Hank’s solution were higher than those for a pure iron, and also higher than the rates reported for homogeneous Fe-Mn alloys.

Prediction of stress-strain curves for TCP/PLLA composites: effect of hydrolysis and strain rate

In this study, effect of hydrolysis in simulated body environment on mechanical behavior of tricalcium phosphate (TCP)/poly(L-lactic acid) (PLLA) composites was analytically characterized. In order to predict stress–strain behavior after hydrolysis, damage of micromechanical analysis proposed by the authors was utilized. In this model, nonlinear behavior in stress–strain relationship was simulated considering interfacial debonding between TCP particle and PLLA matrix. For the purpose of deciding the interfacial strength, such as critical energy release rate, curve fitting was conducted on the result of the composites with 15wt% TCP content at three types of strain rates. Theoretical results on 5 and 10wt% composites using the interfacial strength obtained were in good agreement with experimental results. These results indicated that interfacial strength was dependent only on strain rate and was independent from TCP fraction.

Evaluation of Release and Accumulation of Metal Ions from Titanium and Nickel by Accelerated Dissolution Test in Simulated Body Environments

Evaluation of Release and Accumulation of Metal Ions from Titanium and Nickel by Accelerated Dissolution Test in Simulated Body Environments

タンパク質および細胞を含んだ模擬体液中で繰返し応力を付与した Type 316L ステンレス鋼の溶解と再不働態化

Dissolution and repassivation of type 316L stainless steel during cyclic deformation were examined in a simulated body environment. Samples were exposed to simulated body fluid (SBF) with or without cells, and then subjected to cyclical deformation in the SBF kept at cell culturing condition. The cyclic stress ratio and maximum stress were 0.1 and 300MPa, respectively. Transients of stress, strain and corrosion potential were recorded during the test. The corrosion potential became less noble immediately after the start of the test, but started to increase again after about 10³1000 cycles. The minimum corrosion potential depends on the treatment prior to the deformation: the lowest value was observed for the specimen previously immersed in SBF for 1 day without cells, whereas the highest one was shown by the specimen immersed for 1 week in the presence of cultured cells. This reveals that proteins and cells inhibit metal dissolution during deformation. On the other hand, the time needed for the potential revert to noble was the longest for the sample containing cells, and shortest for the cell-free sample immersed for 1 day. This denotes that proteins and cells also suppress repassivation. [doi:10.2320/matertrans.M2014301]

Degradation behaviors of surface modified magnesium alloy wires in different simulated physiological environments

The degradation behaviors of the novel high-strength AZ31B magnesium alloy wires after surface modification using micro-arc-oxidization (MAO) and subsequently sealing with poly-L-lactic acid (PLLA) in different simulated physiological environments were investigated. The results show the surface MAO micropores could be physically sealed by PLLA, thus forming an effective protection to corrosion resistance for the wires. In simulated gastric fluid (SGF) at a low pH value (1.5 or 2.5), the treated wires have a high degradation rate with a rapid decrease of mass, diameter, mechanical properties and a significant increase of pH value of the immersion fluid. However, surface modification could effectively reduce the degradation rate of the treated wires in SGF with a pH value above 4.0. For the treated wires in simulated intestinal fluid at pH = 8.5, their strength retention ability is higher than that in strong acidic SGF. And the loss rate of mass is faster than that of diameter, while the pH value of the immersion fluid decreases. It should be noted that the modified wires in simulated body environment have the best strength retention ability. The wires show the different degradation behaviors indicating their different degradation mechanisms, which are also proposed in this work.

Yttrium phosphate microspheres with enriched phosphorus content prepared for radiotherapy of deep-seated cancer

Ceramic microspheres composed of β-emitters are useful for in situ radiotherapy of deep-seated cancer by implantation around the tumor. In addition, microspheres 20–30µm in diameter can combine β-emission with the embolization effect. Yttrium phosphate is an attractive candidate material for such microspheres, because both Y and P play roles as β-emitters. The half-life of 31P is known to be much larger than that of 90Y. Therefore, it is expected that yttrium phosphate microspheres with high P content can maintain a longer radiotherapy effect. In the present study, preparation of microspheres with enriched P content has been attempted by water-in-oil emulsions using polyphosphate as a starting material. Yttrium phosphate microspheres with a higher P/Y molar ratio (2.5) than in previously reported YPO4 microspheres were obtained. It was found that emulsification for sufficient time (more than 10min) is necessary to obtain microspheres that are 20–30µm in size. Although the microspheres released Y sparingly, they released larger amounts of P than previously reported YPO4 microspheres in a simulated body environment. Heat treatment at moderate temperature can suppress P release to some extent. Further improvement in chemical durability through surface modification is essential for long-term clinical use.

Characterization and Corrosion Behavior of Multilayer [TiN/TiCN]n Growth on AISI 316LVM Steel

In this paper a study of the corrosion resistance is shown in a physiological medium of multilayer coatings [TiN/TiCN] n with periods bilayers of 1, 50 and 150 deposited on silicon substrates ( 100 ) and stainless steel AISI 316 LVM by the method of RF magnetron reactive sputtering with an RF power ( 13.56 MHz ) and using two targets of Ti and TiC. The electrochemical behavior simulated body environment was evaluated by the technique of using Tafel polarization curves, in Hanks solution as electrolyte. Morphological characterization was performed using scanning electron microscopy (SEM) on silicon substrates (100), also was used to characterize the mechanism of attack on the uncoated steel and coated steels. Was found to be markedly increased corrosion resistance to the deposition of multilayer coatings evidencing the effect of the spatial period ( Λ ) in reducing the degradation of these coatings , the effect was shown for the substrate alloy type stainless steel AISI 316 LVM, confirming the good performance of the variation of the bilayers period.