Preparation of superparamagnetic magnetite nanoparticles by reverse precipitation method: contribution of sonochemically generated oxidants

Magnetic iron oxide nanoparticles were successfully prepared by a novel reverse precipitation method with the irradiation of ultrasound. TEM, XRD and SQUID analyses showed that the formed particles were magnetite (Fe(3)O(4)) with about 10nm in their diameter. The magnetite nanoparticles exhibited superparamagnetism above 200K, and the saturation magnetization was 32.8 emu/g at 300 K. The sizes and size distributions could be controlled by the feeding conditions of FeSO(4).7H(2)O aqueous solution, and slower feeding rate and lower concentration lead to smaller and more uniform magnetite nanoparticles. The mechanisms of sonochemical oxidation were also discussed. The analyses of sonochemically produced oxidants in the presence of various gases suggested that besides sonochemically formed hydrogen peroxide, nitrite and nitrate ions contributed to Fe(II) ion oxidation.

Hydrocarbon decomposition on a hydrophilic TiO2 surface by UV irradiation: spectral and quantitative analysis using in-situ XPS technique

This paper presents valuable evidence in support of the removal of a contaminant hydrocarbon layer adsorbed on photocatalytic TiO2 film by the latter's photo-oxidization. UV light was radiated on an anodic TiO2 film in an atmosphere-controlled chamber, and the film was then transferred to an ultrahigh-vacuum chamber for X-ray photoelectron spectroscopic (XPS) analysis; during the transfer, care was taken to ensure that the film was not exposed to air. This "in situ" setting eliminates the influence of carbon and water adsorptions during the transfer, thus enabling the accurate analysis of the UV-induced surface reaction. The spectral and quantitative results clearly revealed that the adsorbed hydrocarbon was removed from the photocatalytic TiO2 film when the film was irradiated in an oxygen atmosphere. Such removal occurs only in the case of TiO2 films that exhibit superhydrophilicity. This indicates that the removal of hydrocarbon is dependent on the UV-induced hydrophilicity on the film. In situ XPS measurement also presented evidence for UV-induced hydroxide group adsorption, where the adsorption was observed on both the surfaces showing superhydrophilicity and devoid of it.

Mechanical properties and microstructures of β Ti-25Nb-11Sn ternary alloy for biomedical applications

The mechanical properties and microstructures of β Ti-25%Nb-11%Sn ternary alloy rods were investigated for biomedical applications as a function of heat treatment temperature after swaging by an 86% reduction in cross-section area. An as-swaged rod consisting of a β (bcc) single phase shows a low Young's modulus of 53 GPa, which is interpreted in terms of both the metastable composition of the β alloy undergoing neither an athermal ω transformation nor a deformation-induced ω transformation and <110>texture development during swaging. Heat treatment at 673 K (400 °C) for 2h leads to a high strength of approximately 1330 MPa and a high spring-back ratio of yield stress to Young's modulus over 15×10(-3), with acceptable elongation. This high strength is attributable to needle-like α precipitates, which are identified by high-angle annular dark-field scanning transmission electron microscopy (HAADF-STEM) and high-resolution electron microscopy (HREM).

Effect of swaging on Young׳s modulus of β Ti-33.6Nb-4Sn alloy

The effect of swaging on the Young's modulus of β Ti-33.6Nb-4Sn rods was investigated by X-ray diffraction, thermography, microstructural observations, deformation simulator analysis and cyclic tensile deformation. Stress-induced α″ martensite was stabilized by swaging, dependent on the diameter reduction rate during swaging. Thermography and deformation simulator analysis revealed that swaged rods were adiabatically heated, and consequently, stress-induced α″ underwent reverse transformation. Young's modulus, which was measured by the slope of the initial portion of the stress-strain curve, decreased from 56GPa in the hot-forged/quenched rod to 44GPa in the rapidly swaged rod with a high reduction rate and to 45GPa in the gradually swaged rod with a low reduction rate. The tangent modulus, which was measured by the slope of the tangent to any point on the stress-strain curve, decreased with strain even in the linear range of the stress-strain curve of the hot-forged/quenched rod and the rapidly swaged rod, while the tangent modulus remained unchanged for the gradually swaged rod. It was found that Young's moduli in swaged β Ti-33.6Nb-4Sn rods were affected by stabilized α″ martensite. Low Young's modulus of 45GPa and high strength over 800MPa were obtained when the reverse transformation by adiabatic heating was suppressed and the stress-induced α″ was sufficiently stabilized by gradual swaging to a 75% reduction in cross section area.

Bioactive TiNbSn alloy prepared by anodization in sulfuric acid electrolytes

The bioactivity of anodized near-β TiNbSn alloy with low Young's modulus prepared in sulfuric acid electrolytes was examined to explore the osseointegration mechanism with a focus on the role of anodic oxide. Hydroxyapatite (HA) precipitated on the surface of anodic oxide following immersion in Hank's solution, and precipitation accelerated with increase in the sulfuric acid concentration of the electrolyte. HA is formed on the surface of as-anodized oxide without subsequent annealing or hot water (HW) treatment. This outcome differs from that of a previous study using anodized TiNbSn alloy prepared in acetic acid electrolytes requiring for subsequent HW treatment. It was found that the oxide anodized in sulfuric acid electrolyte contains a large amount of internal pores and is highly crystallized thick TiO₂, whereas the same prepared in the acetic acid electrolyte is low crystalline thin TiO₂ containing a small amount of pores. The present anodized TiNbSn alloy is preferred for maintaining the low Young's modulus of the alloy and eliminating the subsequent treatment to increase the Young's modulus. A model to rationalize the bioactivity of the present anodic oxide is proposed based on the series of studies. It is concluded that the sulfuric acid electrolyte is favorable for both HA formation and low Young's modulus, and the bioactivity is attributed to the anodic TiO₂ that facilitates incorporation of bone ingredients.

Microstructures and bond strengths of plasma-sprayed hydroxyapatite coatings on porous titanium substrates

Hydroxyapatite (HA) coating was carried out by plasma spraying on bulk Ti substrates and porous Ti substrates having a Young's modulus similar to that of human bone. The microstructures and bond strengths of HA coatings were investigated in this study. The HA coatings with thickness of 200-250 microm were free from cracks at interfaces between the coating and Ti substrates. XRD analysis revealed that the HA powder used for plasma spraying had a highly crystallized apatite structure, while the HA coating contained several phases other than HA. The bond strength between the HA coating and the Ti substrates evaluated by standard bonding test (ASTM C633-01) were strongly affected by the failure behavior of the HA coating. A mechanism to explain the failure is discussed in terms of surface roughness of the plasma-sprayed HA coatings on the bulk and porous Ti substrates.

Sonochemical immobilization of noble metal nanoparticles on the surface of maghemite: mechanism and morphological control of the products

Aqueous sample solutions containing noble metal ions (HAuCl4, Na2PdCl4, H2PtCl6), polyethyleneglycol monostearate, and magnetic maghemite nanoparticles were irradiated with high power ultrasound. Analyses of the products showed that noble metal ions were reduced by the effects of ultrasound, and the formed noble metal nanoparticles were uniformly immobilized on the surface of the maghemite. The present "one pot process" significantly simplifies the immobilization of noble metal nanoparticles on the surface of supports, compared with the conventional impregnation method. The average diameter of immobilized Au was 7-13 nm, and the diameters of Pd and Pt were several nm. The diameters depended upon the concentration of polyethyleneglycol monostearate and the concentration of noble metal ions, but not upon the maghemite concentration, indicating the possibility of the morphological controls of the products by adjusting these preparation conditions. The measurements of the average diameters and the numbers of immobilized Au nanoparticles obtained under various conditions suggest that the nucleation of Au does not occur on the surface of maghemite, but it might occur in the homogeneous bulk solution.

Effects of intramedullary nails composed of a new β-type Ti-Nb-Sn alloy with low Young's modulus on fracture healing in mouse tibiae

The influence of Young's moduli of materials on the fracture healing process remains unclear. This study aimed to assess the effects of intramedullary nails composed of materials with low Young's moduli on fracture repair. We previously developed a β-type Ti-Nb-Sn alloy with low Young's modulus close to that of human cortical bone. Here, we prepared two Ti-Nb-Sn alloys with Young's moduli of 45 and 78 GPa by heat treatment, and compared their effects on fracture healing. Fracture and nailing were performed in the right tibiae of C57BL/6 mice. The bone healing process was evaluated by microcomputed tomography (micro-CT), histomorphometry, and RT-PCR. We found larger bone volumes of fracture callus in the mice treated with the 45-GPa Ti-Nb-Sn alloy as compared with the 78-GPa Ti-Nb-Sn alloy in micro-CT analyses. This was confirmed with histology at day 14, with accelerated new bone formation and cartilage absorption in the 45-GPa Ti-Nb-Sn group compared with the 78-GPa Ti-Nb-Sn group. Acp5 expression was lower in the 45-GPa Ti-Nb-Sn group than in the 78-GPa Ti-Nb-Sn group at day 10. These findings indicate that intramedullary fixation with nails with a lower Young's modulus offer a greater capacity for fracture repair. Our 45-GPa Ti-Nb-Sn alloy is a promising material for fracture treatment implants. © 2018 Wiley Periodicals, Inc. J Biomed Mater Res Part B: Appl Biomater, 106B: 2841-2848, 2018.

Effects of elastic intramedullary nails composed of low Young's modulus Ti-Nb-Sn alloy on healing of tibial osteotomies in rabbits

Intramedullary nailing is widely performed for internal fixation of fractures. The applicable elasticity of materials composing intramedullary nails remains unclear. The present study aimed to evaluate the effects of the elastic property of β-type titanium alloy nails on fracture healing compared with conventional Ti-6Al-4V alloy nails using a rabbit tibial osteotomy model. Two types of intramedullary nails composed of β-type Ti-Nb-Sn alloy (Young's modulus: 37 GPa) or Ti-6Al-4V alloy (Young's modulus: 110 GPa) were used for osteotomy fixation in the tibiae of rabbits. At 4, 8, and 16 weeks postoperatively, microcomputed tomography (micro-CT) and three-point bending tests were performed. Micro-CT images showed that the callus volume was significantly larger in the Ti-Nb-Sn alloy group at 4 and 8 weeks. The callus bone mineral density did not differ at each time point. In mechanical testing, the maximum load was significantly higher at all time points in the Ti-Nb-Sn alloy group. Taken together, the elastic intramedullary nails composed of Ti-Nb-Sn alloy improved the mechanical properties of the bone healing site from the early phase to the remodeling phase. Adequate Young's modulus of the Ti-Nb-Sn alloy enhanced fracture union and bone strength restoration. The Ti-Nb-Sn alloy is a promising biomaterial for fracture fixation devices. © 2018 Wiley Periodicals, Inc. J Biomed Mater Res Part B: Appl Biomater, 2018. © 2018 Wiley Periodicals, Inc. J Biomed Mater Res Part B: Appl Biomater 107B: 700-707, 2019.

β-type TiNbSn Alloy Plates With Low Young Modulus Accelerates Osteosynthesis in Rabbit Tibiae

BACKGROUND

Ti6Al4V alloy, which is commonly used for biomedical applications, has a Young modulus (110 GPa) that is higher than that of human cortical bone (11 to 20 GPa). Using an implant with a material with a low Young modulus that enhances load sharing by the bone even more than those made of Ti6Al4V could be beneficial for bone healing and further reduce the potential for stress shielding. A new β-type TiNbSn alloy has a low Young modulus of approximately 40 to 49 GPa. However, whether the new titanium alloy with a lower Young modulus is advantageous in terms of fracture healing has not been assessed, and a small-animal model seems a reasonable first step in its assessment.

QUESTIONS/PURPOSES

To assess the impact of a TiNbSn alloy plate with a lower Young modulus compared with a Ti6Al4V alloy plate on fracture healing, we evaluated: (1) bony bridging and callus volume, (2) new bone formation and remaining cartilage tissue, (3) osteoblast activity in the callus, and (4) mechanical strength and stiffness of the callus in bending.

METHODS

Fracture plates manufactured from TiNbSn and Ti6Al4V alloys, which have Young moduli of 49 GPa and 110 GPa, respectively, were compared. The main reason for using rabbits was the high reliability of the three-point bending mechanical test of the rabbit tibia. Forty-two male Japanese white rabbits weighing 2.8 to 3.4 kg were anesthetized. A 5-cm skin incision was made on the medial side in the mid-diaphysis of the right tibia. Eight-hole plates were used, which were 42 mm long, 5 mm wide, and 1.2 mm thick. Plate fixation was performed using three proximal and three distal screws. After the plate was installed, an osteotomy was performed using a 1-mm-wide wire saw to create a standardized tibial transverse osteotomy model with a 1-mm gap. Bone healing was quantitatively assessed by two nonblinded observers using micro-CT (bony bridging and callus volume), histomorphometry (new bone formation and remaining cartilage tissue), immunohistochemistry (osteoblast activity), and mechanical testing (mechanical strength and stiffness in bending). Measurements on nondemineralized specimens were descriptive statistics due to their small number. Four weeks after osteotomy and fixation, 30 rabbits were euthanized to undergo micro-CT and subsequent mechanical testing (n = 12), histomorphometry and immunohistochemistry with demineralized specimens (n = 12), and histomorphometry with a nondemineralized specimen (n = 6). Eight weeks postoperatively, 12 rabbits were euthanized for micro-CT and subsequent mechanical testing.

RESULTS

Intramedullary fracture calluses treated with TiNbSn alloy plates had larger bone volumes and more numerous bridging structures than those treated with Ti6Al4V alloy plates at 4 weeks after osteotomy (Ti6Al4V alloy versus TiNbSn alloy: 30 ± 7 mm 3 versus 52 ± 14 mm 3 , mean difference 22 [95% CI 9 to 37]; p = 0.005; ICC 0.98 [95% CI 0.95 to 0.99]). Histologic assessments demonstrated there was greater new bone formation (total callus: Ti6Al4V versus TiNbSn: 16 ± 4 mm 2 versus 24 ± 7 mm 2 , mean difference 8 [95% CI 1 to 16]; p = 0.04; ICC 0.98 [95% CI 0.93 to 0.99]; intramedullary callus: Ti6Al4V versus TiNbSn: 6 ± 4 mm 2 versus 13 ± 5 mm 2 , mean difference 7 [95% CI 1 to 13]; p = 0.02; ICC 0.98 [95% CI 0.95 to 0.99]) and a higher number of osteocalcin-positive cells (Ti6Al4V alloy versus TiNbSn alloy: 1397 ± 197 cells/mm 2 versus 2044 ± 183 cells/mm 2 , mean difference 647 [95% CI 402 to 892]; p < 0.001; ICC 0.98 [95% CI 0.95 to 0.99]) in the TiNbSn alloy group than in the Ti6Al4V alloy group. At 4 weeks after osteotomy, both bone strength and stiffness of the healed bone in the TiNbSn alloy group were higher than those in the Ti6Al4V alloy group (maximum load: Ti6Al4V alloy versus TiNbSn alloy: 83 ± 30 N versus 127 ± 26 N; mean difference 44 [95% CI 8 to 80]; p = 0.02; stiffness: Ti6Al4V alloy versus TiNbSn alloy: 92 ± 43 N/mm versus 165 ± 63 N/mm; mean difference 73 [95% CI 4 to 143]; p = 0.047). Eight weeks after osteotomy, no between-group differences were observed in the strength and stiffness of the healed bone.

CONCLUSION

The results of this study indicate that TiNbSn alloy plate with a lower Young modulus resulted in improved bone formation and stiffer callus during the early phase (4 weeks after surgery) but not the later phase (8 weeks after surgery) of bone healing.

CLINICAL RELEVANCE

An overly stiff plate may impair callus formation and bone healing. The TiNbSn alloy plate with a low Young modulus improves the early formation of new bone and stiff callus at the osteotomy site compared with the Ti6Al4V alloy plate in the healing process, which may promote bone repair. TiNbSn alloy may be a promising biomaterial for fracture treatment devices. Further research to address concerns about the strength of TiNbSn alloy plates, such as fatigue life and plate fracture, will be necessary for clinical applications, including mechanical tests to verify fatigue life and validation in larger animals with greater body weight.

Acceleration of Fracture Healing in Mouse Tibiae Using Intramedullary Nails Composed of β-Type TiNbSn Alloy with Low Young's Modulus

The optimal Young's modulus of material of orthopedic devices for fracture treatment is still unknown. The purpose of present study was to evaluate the impacts of intramedullary nails composed of a titanium alloy with low Young's modulus, on accelerating fracture healing compared with stainless steel with high Young's modulus. A β-type TiNbSn alloy with a low Young's modulus close to that of human cortical bone was developed for clinical application. TiNbSn alloy with a Young's modulus of 45 GPa and stainless steel with a Young's modulus of 205 GPa were compared, with respect to the impacts on fracture healing. Fracture and fixation using intramedullary nail were performed on the right tibiae of C57BL/6 mice. The assessment of bone healing was performed via micro-computed tomography, histomorphometry, and quantitative reverse transcription polymerase chain reaction. In micro-computed tomography, larger bone volumes were observed in the fracture callus treated with TiNbSn alloy in comparison with those treated with stainless steel. Histological assessments confirmed accelerated cartilage absorption and new bone formation in the TiNbSn alloy group compared with the stainless steel group. The expression of Col1a1, Runx2, Dkk1, and Acp5 was higher in the TiNbSn alloy group, while that of Col2a1 and Col10a1 was lower in the late phase. The present study demonstrated that the fixation by intramedullary nails with TiNbSn alloy offered an accelerated fracture healing with promotion of bone formation via increased Runx2 expression. TiNbSn alloy might be a promising material for fracture treatment devices.

Antibacterial Activity of an Anodized TiNbSn Alloy Prepared in Sodium Tartrate Electrolyte

In this study, we anodized a TiNbSn alloy with low Young’s modulus in an electrolyte of sodium tartrate with and without hydrogen peroxide (H2O2). The photo-induced characteristics of the anodized alloy were analyzed for crystallinity and electrochemical conditions with comparisons to the effect with the addition of H2O2. The antibacterial activity was evaluated using methicillin-resistant Staphylococcus aureus and other pathogenic bacteria according to ISO 27447, and time decay antibacterial tests were also conducted. The anodized oxide had a porous microstructure with anatase- and rutile-structured titanium dioxide (TiO2). In contrast, the peaks of rutile-structured TiO2 were accelerated in the anodized TiNbSn alloy with H2O2. The formation of hydroxyl radicals and methylene blue breaching performance under ultraviolet irradiation was confirmed in the anodic oxide on TiNbSn alloy with and without H2O2. The anodic oxide on TiNbSn alloy had a robust antibacterial activity, and no significant difference was detected with or without H2O2. We conclude that anodized TiNbSn alloy with sodium tartrate electrolyte may be a functional biomaterial with a low Young’s modulus and an antibacterial function.