Immersion In Aqueous Solution Research Articles

Highly Porous Gelatin Reinforced 3D Scaffolds for Articular Cartilage Regeneration.

3D highly porous (93% total porosity) gelatin scaffolds were prepared according to a novel, simple method, which implies gelatin foaming, gelification, soaking into ethanol and successive freeze-drying. Reinforcement of the as-prepared scaffolds (GEL) was performed through immersion in aqueous solutions at different gelatin concentrations. Reinforcement solutions with and without genipin addition allowed to prepare two series of samples:cross-linked and uncross-linked samples, respectively. The amount of gelatin adsorbed onto the reinforced samples increases as a function of gelatin concentration in solution and provokes a drastic improvement of the compressive modulus and collapse strength up to values of about 30 and 4 MPa, respectively. The open and interconnected porosity, although slightly reduced, is still of the order of 80% in the samples reinforced with the highest concentration of gelatin. Water uptake ability evaluated after immersion in PBS for 20 s decreases with gelatin reinforcement. The presence of genipin in cross-linked samples reduces gelatin release and stabilizes the scaffolds in solution. Chondrocytes from human articular cartilage adhere, proliferate, and penetrate into the scaffolds. The evaluation of differentiation markers both on the supernatants of cell culture and by means of quantitative polymerase chain reaction (qPCR) indicates a dose-dependent promotion of cell differentiation.

The stabilization of electrospun chitosan nanofibers by reversible acylation

Chitosan nanofibers fabricated by electrospinning are contaminated by acidic anions from the acid spinning solution, leading to instability of the nanofibers in aqueous solutions, and the traditional fiber treatment method will also lead to the deterioration of the nanostructure. Here we demonstrate a novel approach to removing the acidic anions with full preservation of the nanofibrous structure. The as-spun nanofibers are first protected (stabilized) by reversible acylation. Second, contaminants are then eliminated by hydrolysis; finally, acylation is reversed. Chemical analysis showed the removal of the acidic anions and the graft and removal of acyl groups. Morphological analysis showed that the reversibly acylated fibers had diameters <150 nm and nanofiber structure was maintained after immersion in aqueous solution. The membranes also were compatible with bone cells in culture. The resultant pure chitosan nanofibers show excellent stability in aqueous solution and exhibit broad potential in biomedical applications.

Click‐Chemistry Based Multi‐Component Microarrays by Quill‐Like Pens

We demonstrate the generation of multi‐component spot microarrays by blotting different ink solutions via quill‐like pens. The obtained arrays are immobilized by click‐chemistry in form of the copper(I)‐catalyzed azide‐alkyne cycloaddition and remain stable against washing and immersion in aqueous solution. The average spot radius ranges from 10 to 20 μm and is about an order of magnitude smaller than in currently commercially applied arraying techniques, effectively bridging the gap to high resolution methods as dip‐pen nanolithography and polymer pen lithography. The use of the quill‐like‐pen‐generated spot microarrays as binding assay is demonstrated by capturing of streptavidin from solution and by bioactive sandwich structures from neutravidin and biotin‐labeled fibronectin. Thus, our multi‐component spot microarrays have ideal dimensions and biochemical properties to accommodate (single) cells. Additionally, the building up of the cell‐recruiting protein sandwich structure on top of the basic spot microarray allows for the highly selective adhesion of fibroblasts. This results then in ordered (single) cell arrays, demonstrating the bio‐compatibility and high throughput of this multi‐component spot microarray platform.

Micrometer-sized mesoporous diamond spherical particles

Micrometer-sized porous diamond spherical particles (PDSPs) were fabricated from nanodiamond (ND) particles using spray drying and microwave plasma-assisted chemical vapor deposition (MPCVD). Nitrogen gas sorption measurement revealed that the PDSP fabricated from 5 nm detonation ND particles had a Brunauer–Emmett–Teller (BET) surface area of ca. 300 m 2 g − 1 and a narrow pore diameter distribution around 10 nm. Nitrogen sorption analysis of PDSP fabricated from various ND particle sizes (diameters from 20 to 50 nm) showed that the BET surface area decreased (200–85 m 2 g − 1 ) and the average pore diameter increased (4.6–9.3 nm) as the ND diameter increased from 20 to 50 nm. Calculation with a simple model revealed that the pores of the PDSP were derived from the interparticle space of the NDs. The PDSP was durable to immersion in aqueous solutions of HF and NaOH, which indicates the extremely high chemical stability of the diamond-based mesoporous material. The PDSP surface was modified with octadecyl groups using a photochemical method. A column packed with the modified PDSP was successfully employed in a reverse phase high performance liquid chromatography (HPLC) column, and the successful separation of organic compounds was demonstrated with a water/acetonitrile mixture mobile phase. • Micrometer-sized mesoporous diamond spherical particles were fabricated. • Pore size can be controlled by nanodiamond particle size used. • The porous diamond spherical particle (PDSP) exhibited extreme chemical stability. • The modified PDSP was applied to HPLC column packing material.

Chemical force microscopy of stimuli-responsive adhesive copolymers

Atomic force microscopy with chemically sensitive tips was used to investigate the hydrophobic and electrostatic interaction forces of a stimuli-responsive adhesive polymer, and their dynamic changes in response to water immersion and salt concentration. Block copolymer-filled coatings were obtained by incorporating an amphiphilic block copolymer containing a polydimethylsiloxane (PDMS) block and a poly(2-(dimethylamino)ethyl methacrylate) (PDMAEMA) block in a PDMS matrix. Topographic images of fresh samples revealed the presence of nanoscale domains associated with the presence of copolymers, covered by a thin layer of PDMS. Prolonged (30 days) immersion in aqueous solution led to the exposure of the hydrophilic PDMAEMA chains on the surface. Using adhesion force mapping with hydrophobic tips, we showed that fresh samples were uniformly hydrophobic, while aged samples exhibited lower surface hydrophobicity and featured nanoscale hydrophilic copolymer domains. Force mapping with negatively charged tips revealed remarkable salt-dependent force plateau signatures reflecting desorption of polyelectrolyte copolymer chains. These nanoscale experiments show how solvent-induced conformational changes of stimuli-responsive copolymers can be used to modulate surface adhesion.

Synthesis and characterization of europium-containing luminescent bioactive glasses and evaluation of in vitro bioactivity and cytotoxicity

Luminescent europium-containing bioactive glasses (EuBG) based on the 58 %SiO2–33 %CaO–9 %P2O5 (in mass, %) system were synthesized using sol–gel technique by adding Eu2O3 in silica network. The structural, textural and optical properties, as well as in vitro bioactivity and biocompatibility of the material were characterized using various methods. The results show that all the Eu-containing bioactive glass materials exhibit an amorphous structure, large specific surface area, relatively uniform pore size distribution and high in vitro bioactivity, similar to the conventional sol–gel bioactive glass. More importantly, the addition of Eu2O3 endow the material with a luminescent property even after immersion in aqueous solution and the luminescent intensity increases with the increase of Eu2O3 content. The cytotoxicity assay indicates that pure EuBG extract significantly inhibit the growth of rat marrow mesenchymal stem cells (rMSCs), while 25 % concentration of the extract diluted by culture medium could significantly improve the proliferation of rMSCs in comparison with pure medium. According to the above results, the material presents excellent apatite-forming activity, luminescent property and biocompatibility, demonstrating their potential applications in the fields of bone regeneration and drug delivery system.

Facile fabrication of a robust super-hydrophobic surface on magnesium alloy

A super-hydrophobic surface was successfully fabricated on magnesium alloy by electrodeposition of Zn–Co coating from choline chloride-based ionic liquid and subsequent surface modification. The water contact angle (CA) was measured to be as high as 152̊. Based on surface analysis by scanning electron microscope (SEM), X-ray photoelectron spectroscopy (XPS) and Fourier-transform infrared (FTIR), the super-hydrophobicity can be attributed to both the rough and porous micro- and nano-scale binary structural Zn–Co coating and surface enrichment of low surface energy stearic acid (SA). The corrosion behavior was investigated with potentiodynamic polarization measurements and it was found that the super-hydrophobic coating considerably improved the corrosion resistant performance of magnesium alloy in 0.1mol/L NaCl solution. In addition, the stability of the super-hydrophobic property was investigated by immersion in aqueous solution, finger touching and abrasion with sandpaper. The results showed that the super-hydrophobic coating exhibited high stability in aqueous solution, the rough surface textures were retained and the coating still exhibited a large contact angle after mechanical destroy.

Biofabrication of multi-material anatomically shaped tissue constructs

Additive manufacturing in the field of regenerative medicine aims to fabricate organized tissue-equivalents. However, the control over shape and composition of biofabricated constructs is still a challenge and needs to be improved. The current research aims to improve shape, by converging a number of biocompatible, quality construction materials into a single three-dimensional fiber deposition process. To demonstrate this, several models of complex anatomically shaped constructs were fabricated by combined deposition of poly(vinyl alcohol), poly(ε-caprolactone), gelatin methacrylamide/gellan gum and alginate hydrogel. Sacrificial components were co-deposited as temporary support for overhang geometries and were removed after fabrication by immersion in aqueous solutions. Embedding of chondrocytes in the gelatin methacrylamide/gellan component demonstrated that the fabrication and the sacrificing procedure did not affect cell viability. Further, it was shown that anatomically shaped constructs can be successfully fabricated, yielding advanced porous thermoplastic polymer scaffolds, layered porous hydrogel constructs, as well as reinforced cell-laden hydrogel structures. In conclusion, anatomically shaped tissue constructs of clinically relevant sizes can be generated when employing multiple building and sacrificial materials in a single biofabrication session. The current techniques offer improved control over both internal and external construct architecture underscoring its potential to generate customized implants for human tissue regeneration.

Studies on the effect of Zn ions on the corrosion behavior of iron-base alloys relevant to desalination and power plant conditions

The corrosion behavior of mild steel and AISI 304L SS in the presence of dissolved Zn ions under different experimental conditions have been investigated. Experimental conditions include: variation in aqueous medium, Zn ions concentration, pH, dissolved oxygen, and flow condition. The variation in corrosion rate in the presence of varying concentrations of Zn ions was determined using weight loss technique and spectrophotometric analysis of iron ions entered into the test solutions after completion of immersion. The pH of the test solutions was also monitored during the entire period of immersion. The Zn ions present in the test solutions after completion of immersion were estimated using atomic absorption spectrophotometer (AAS). Open circuit potential (OCP) measurements and potentiodynamic polarization (PDP) measurements were carried out to find out the role of Zn ions on the corrosion behavior of mild steel and SS 304L. The surface morphology of steel before and after immersion in aqueous solution containing Zn ions was also examined using scanning electron microscope (SEM) and energy dispersive X-ray spectroscopy (EDS). The influence of Zn ions on the corrosion behavior of mild steel is quite pronounced and show interesting trends whereas SS 304L is unaffected both in distilled water or artificial seawater.

Developing of a dehydration process for bovine leather to obtain a new collagenous material

Abstract The aim of the present work is to develop a dehydration process for bovine hide to obtain a new collagenous material for use in the leather industry. What is obtained through this new process is a dry and very porous collagenous substrate which allows the application of tanning and retanning chemicals by immersion in aqueous solutions. When compared to existing, traditional processes, there are economic and environmental advantages resulting from the use of this new material. More specifically, the new process results in reductions in water use (21.7%), chemical use (46.9%) and processing time (21%).

Durable PEDOT:PSS films obtained from modified water-based inks for electrochemical sensors

Printing of conducting polymer films from water-based inks is a powerful method that can facilitate the fabrication of various types of electrochemical sensors. This paper reports on the use of ethylene glycol and quaternary ammonium salts as additives to water-based poly(3,4-ethylenedioxythiophene) poly(styrenesulfonate) (PEDOT:PSS) inks in order to obtain conducting polymer films with improved adhesion to a carbon-based electrode substrate in aqueous environment. The modified PEDOT:PSS films deposited on glassy carbon were studied in aqueous solutions by cyclic voltammetry, electrochemical impedance spectroscopy, and potentiometry. It was found that PEDOT:PSS films modified with ethylene glycol and quaternary ammonium salts exhibit excellent adhesion to glassy carbon even after immersion in aqueous solutions for more than two months. The modified PEDOT:PSS films were electroactive, showed relatively fast ion transport properties, and were successfully applied as solid-contact material in lead(II)-selective electrodes.

Fabrication of Carboxylated Silicon Nitride Sensor Chips for Detection of Antigen–Antibody Reaction Using Microfluidic Reflectometric Interference Spectroscopy

In this study, we report label-free detection of alpha-fetoprotein (AFP), which has been used as a biomarker for hepatocellular carcinoma, by a microfluidic reflectometric interference spectroscopy (RIfS) system adopting a simple halogen light source and an inexpensive silicon-based sensor chip. Introduction of carboxy groups on a silicon nitride sensor chip to immobilize anti-AFP monoclonal antibody (anti-AFP) was carried out simply by immersion in aqueous solution containing triethoxysilylpropylmaleamic acid bearing a carboxy group and a silanol group. The RIfS system with the anti-AFP-immobilized sensor chip was found to give a reversible response through 100 on/off cycles using a regeneration buffer with high reproducibility (coefficient of variation (CV) = 5.7%). The limit of detection (LOD) of AFP was 100 ng mL(-1), and the measurement range spanned 3 orders of magnitude. Furthermore, the sensor chip showed no cross-reactivity with human serum albumin, Immunoglobulin G, transferrin, or fibrinogen at 100 μg mL(-1) without the use of blocking reagents such as bovine serum albumin. Consequently, the proposed RIfS system is a potentially effective tool for biomarker detection and in vitro diagnostics.

Lipid adlayer organization mediated by a liquid overlayer

We report on the formation of a chemically bound 1,2-dimyristoyl-sn-glycero-3-phosphocholine (DMPC) monolayer on modified Au and silica surfaces, and changes in the organization of the interfacial lipid layer associated with immersion in aqueous solution. We have studied the interface using steady state and time resolved fluorescence spectroscopy, water contact angle and optical ellipsometry measurements, and electrochemical methods. Our data reveal that the DMPC adlayer in contact with air forms a relatively well organized interface that mediates the rotational motion of perylene. In the presence of an aqueous overlayer, perylene reorientation becomes more rapid, consistent with a reduction in the organization of the interfacial lipid adlayer. One implication of this finding is that the interfacial adlayer is less than a uniform monolayer, which is confirmed by electrochemical data. Our data underscore the importance of water in mediating the organization of interfacial lipid adlayers.

Antifouling foldable acrylic IOLs loaded with norfloxacin by aqueous soaking and by supercritical carbon dioxide technology

Cataracts treatment usually involves the extraction of the opaque crystalline lens and its replacement by an intraocular lens (IOL). A serious complication is the occurrence of endophthalmitis, a post-surgery infection mainly caused by Staphylococcus epidermidis, Staphylococcus aureus, and Pseudomonas aeruginosa. IOLs having the ability to load and to release norfloxacin in a controlled way and at efficient therapeutic levels may help to overcome these issues. In this work, acrylic hydrogels combining 2-hydroxyethyl methacrylate (HEMA) and 2-butoxyethyl methacrylate (BEM) at various ratios were prepared to attain biocompatible networks that can be foldable even in the dry state and thus insertable through minor ocular incision, and that load therapeutic amounts of norfloxacin. Acrylamide (AAm) and methacrylic acid (MAAc) were also incorporated as functional comonomers in small proportions. Water sorption, contact angle, protein adsorption, and optical properties of the networks were characterized. BEM notably decreased the Tg of the networks, but also the loading by immersion in aqueous solution (presoaking). Then, a scCO2-based impregnation/deposition (SSI) method was implemented to improve the uptake of the drug. Loading capacities were discussed in terms of the comonomers composition and the employed method and operational conditions. The networks prepared with HEMA/BEM 20:80 vol/vol and processed with supercritical fluids combine adequate mechanical properties, biocompatibility and norfloxacin loading/release, and seem to be suitable for developing norfloxacin-eluting IOLs.

New promising composite materials useful in the adsorption of Cu(II) in ethanol based on cellulose and cellulose acetate

This work describes for the first time the synthesis and characterization of new promising materials based on cellulose (Cel) and cellulose acetate (Celac), previously modified with aluminum oxide (CelAl and CelacAl) and post functionalized with 1,4-diazabicyclo [2.2.2] octane-n-propyltrimethoxysilane chloride (SiDbCl2), resulting the chemically modified hybrid materials CelAl/SiDbCl2 and CelacAl/SiDbCl2. The materials have shown to be useful in the adsorption of CuCl2 from ethanol, presenting high effective adsorption capacity. In the adsorption process, the copper ions diffuse into the solid solution interface and are retained as anionic complexes CuCl 3 − or CuCl 4 2− . An expressive effective adsorption capacity tQ, as well as the stability constants β1 and β2, were found for both adsorbents: (a) CelAl/DbCl2: tQ = 0.33 × 10−3 mol g−1, log β1 = 4.23 (±0.04) and log β2 = 6.99 (±0.03); (b) CelacAl/DbCl2: tQ = 0.48 × 10−3 mol g−1, log β1 = 5.1 (±0.1) and log β2 = 8.3 (±0.1). Both adsorbent materials are potentially useful in the pre-concentration and further analysis of Cu(II) present in trace amounts in ethanol, extensively used as an automotive fuel in Brazil. Regeneration of the adsorbents requires a very simple procedure consisting in their immersion in aqueous solution which causes the immediate release of the Cu(OH2) n 2+ species to the solution phase.

Degradable alginate hydrogels crosslinked by the macromolecular crosslinker alginate dialdehyde

Alginate dialdehyde (ADA) biopolymers possessing a degree of oxidation of either 10 or 50% (10-ADA and 50-ADA, respectively) were characterized using FTIR, XPS and SEC. The aldehyde vibrational mode at 1740 cm−1 was observed only in ADA which had been equilibrated under ambient conditions while dry samples did not display this band. Spectral changes, both FTIR and XPS, were consistent with formation of hemiacetal moieties. The two types of ADA (10-ADA and 50-ADA) were used as macromolecular crosslinkers to form labile covalent crosslinks in alginate hydrogels. The compositions and properties of the hydrogels were explored through measurement of water uptake and stability in aqueous solution, and characterising the internal structure and mechanical properties by cryogenic scanning electron microscopy and tensile testing, respectively. A decrease in water content was observed when using 50-ADA as compared to 10-ADA correlating with a higher number of crosslinks formed in the hydrogel incorporating 50-ADA. Water uptake also correlated with the amount of 50-ADA incorporated. All ADA–alginate hydrogels displayed short term stability of 3 days after immersion in aqueous solution. The stability of the 50-ADA containing hydrogel was enhanced by introducing ionic crosslinking. Tensile properties of the hydrogels were found to be dependent on the overall polymer density and uniformity of the crosslinking.

An improved terthiophene conducting polymer for DNA-sensing

The synthesis of an improved terthiophene monomer functionalized with acrylic acid and a methylhydroxy group, 3-[3′,3‴-bis(hydroxymethyl)-2′:2″,5″:2‴-terthiophene)-3″-yl](E)acrylic acid, (HTAA), and its electropolymerization into a conducting polymer is described and evaluated as a label-free DNA sensor. The aim was to construct an improved thiophene-based conducting polymer whose microstructure could mitigate the collapse in aqueous solution seen in similar previously made thiophene-based conducting polymers. The effects of immersion in aqueous solution assessed by cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS) were complex. The microstructure collapse was significantly mitigated compared to previously made terthiophene polymers but the observed behaviour was dependent on the dopant anion. With a hydrophobic, non-exchangeable anionic dopant, bis-trifluoromethanesulfonimidate, (CF 3) 2(SO 2) 2 −, the polymer film developed a multilayer structure. Electrochemical activity towards the solution redox couple Fe(CN) 6 3−/4− was sustained but with a significant anodic shift of redox potential. A DNA hybridisation response was observed with the hydrophobic dopant but not with the hydrophilic dopant. We have demonstrated that, by attention to both the nature of the polymer and to the choice of dopant anion, the effects of solvent-induced microstructure collapse in aqueous solution on the DNA sensor performance can be mitigated.

Electrochemical Impedance Spectroscopy Studies of Organic-Solvent-Induced Permeability Changes in Nanoporous Films Derived from a Cylinder-Forming Diblock Copolymer

In this paper we report electrochemical investigations of the influence of organic solvents dissolved in aqueous solution on the permeability of nanoporous films derived from a cylinder-forming polystyrene-poly(methyl methacrylate) diblock copolymer (CF-PS-b-PMMA). The nanoporous films (ca. 30 nm in pore diameter) were prepared on planar gold electrodes via UV-based degradation of the cylindrical PMMA domains of annealed CF-PS-b-PMMA films (30-45 nm thick). The permeability of the electrode-supported nanoporous films was assessed using cyclic voltammetry and electrochemical impedance spectroscopy (EIS). The faradic current of Fe(CN)(6)(3-/4-) decreased upon immersion in aqueous solutions saturated with toluene or methylene chloride (5.8 mM and 0.20 M, respectively). EIS data indicated that the decrease in faradic current mainly reflected an increase in the pore resistance (R(pore)). In contrast, R(pore) did not change in a saturated n-heptane solution, 0.17 M ethanol, or 5.8 mM aqueous solutions of methylene chloride, diethyl ether, methyl ethyl ketone, or ethanol. Atomic force microscopy images of a nanoporous film in aqueous solution with and without 5.8 mM toluene showed a reversible change in the surface morphology, which was consistent with a toluene-induced change in R(pore). The solvent-induced increase in R(pore) was attributed to the swelling of the nanoporous films by the organic solvents, which decreased the effective pore diameter. The reversible permeability changes suggest that the surface of CF-PS-b-PMMA-derived nanoporous films can be functionalized in organic environments without destroying the nanoporous structure. In addition, the solvent-induced swelling may provide a simple means for controlling the permeability of such nanoporous films.

Aligned Growth of Zinc Oxide Nanorods on Catalyst-Seeded Si Substrate by Aqueous-Solution Immersion Method

We report an optimisation of reaction conditions leading to successful growth of aligned ZnO nanorods by a simple aqueous immersion method. Si substrates were immersed in aqueous Zn2+ solution at various temperatures ranging between 50 - 90°C and at various immersion times. Degree of crystallisation, thermal decomposition, surface morphology and crystallite size were analysed by FT-IR, TGA, SEM and XRD. Seeded noble metals like gold, platinum and nickel on Si substrate were found to improve the vertical alignment of rods’ growth and reduce the diameter of ZnO nanorods.

Liquid phase formation of alkyl- and perfluoro-phosphonic acid derived monolayers on magnesium alloy AZ31 and their chemical properties

Alkyl- and perfluoro-phosphonic acid derived SAMs were successfully formed on Mg alloy by liquid phase method for the first time. The chemical and anticorrosive properties of the prepared SAMs on magnesium alloys were characterized using contact angle measurements, X-ray photoelectron spectroscopy (XPS), atomic force microscopy (AFM), and electrochemical measurements. Water contact angle measurements revealed that the maximum advancing/receding water contact angles of n-octyl (OP: CH3(CH2)7PO(OH)2), n-dodecyl (DP: CH3(CH2)11PO(OH)2), n-octadecyl (ODP: CH3(CH2)17PO(OH)2) phosphonic acid, and 2-(perfluorohexyl)ethyl (PFEP: CF3(CF2)5CH2CH2PO(OH)2) phosphonic acid were 105.1/64.7°, 108.3/69.6°, 111.9/75.2°, and 115.2/67.4° respectively. In the case of alkylphosphonic acid SAMs (OP, DP, and ODP), the advancing and receding water contact angles increased with an increase in the preparation time. The angle-resolved XPS (AR-XPS) data revealed that the film thicknesses of the OP, DP, ODP, PFEP on Mg alloy were estimated to be 0.8, 1.2, 1.7, and 1.1nm, respectively. The XPS O 1s data support that the phosphonic acid derived SAM is covalently bound to the oxide or hydroxide surface of the Mg alloy in a monodenate or bidenate manner. Chemical stability of the alkyl- and perfluoro-phosphonic acid modified Mg alloy surfaces was investigated using aqueous solutions at pH=4.0, 7.0, and 10.0. The contact angles of OP, DP, and PFEP modified Mg surface decreased rapidly within the first 5min after immersion in all the aqueous solutions and were less than 20°. On the other hand, the contact angles of the ODP modified Mg alloy after immersion in aqueous solutions at pH 4, 7 and 10 for 5min were 45.1°, 89.3,° and 85.5°, respectively. The ODP modified Mg alloy had highest chemical stability in four types of the phosphonic acid derived SAMs used in this study, indicating that the molecular density of ODP on Mg alloy would be higher than those of OP, DP, PFEP on Mg alloy. The corrosion resistance of ODP modified Mg alloy was investigated by potentiodynamic polarization curve measurements. The ODP modified Mg alloy exhibits protective properties in a solution containing Cl− ions compared to unmodified Mg alloy.