Preparation and characterization of biomedical highly porous Ti-Nb alloy.

The compressive strength and the biocompatibility were assessed for the porous Ti-25 wt%Nb alloy fabricated by the combination of the sponge impregnation technique and sintering technique. The alloy provided pore sizes of 300-600 µm, porosity levels of 71 ± 1.5%, in which the volume fraction of open pores was 94 ± 1.3%. The measurements also showed that the alloy had the compressive Young's modulus of 2.23 ± 0.5 GPa and the strength of 98.4 ± 4.5 MPa, indicating that the mechanical properties of the alloy are similar to those of human bone. The scanning electron microscopy (SEM) observations revealed that the pores were well connected to form three-dimension (3D) network open cell structure. Moreover, no obvious impurities were detected in the porous structure. The experiments also confirmed that rabbit bone mesenchymal stem cells (MSCs) could adhere and proliferate in the porous Ti-25 wt%Nb alloy. The interactions between the porous alloy and the cells are attributed to the porous structure with relatively higher surface. The suitable mechanical and biocompatible properties confirmed that this material has a promising potential in the application for tissue engineering.

Fabrication of multilevel porous structure networks on Nb-Ta-Ti alloy scaffolds and the effects of surface characteristics on behaviors of MC3T3-E1 cells.

Porous Nb-25Ta-25Ti alloys (60% porosity and 100-600 µm pore size) for bone implant applications were manufactured combining impregnation and sintering methods. Surfaces with porous micro-nanostructured networks on Nb-Ta-Ti alloys were successfully modified by various surface pre-treatments (acid etching, alkali-heat treatment and annealing treatment). Surface characteristics and Ca-P layer deposition behaviors of the multilevel structured porous Nb-Ta-Ti alloys were investigated by conducting various tests, including x-ray diffraction, scanning electron microscopy, energy-dispersive x-ray, atomic force microscopy and optical contact angle measurement. In particular, bulk Nb-Ta-Ti alloys were also used as mutual control. The results demonstrated that the porous alloy exhibited a unique multilevel porous structure with macro-networks and micro-pits after pre-treatments. The surface passive TiO2/Nb2O5/Ta2O5layers on Nb-Ta-Ti alloys were partially dissolved by the corrosive attack of hydroxyl ions during alkali heat treatment. In addition, subsequent annealing treatment increased the density of the gel layers formed during alkali heat treatment. After immersion in SBF for 14 d, a continuous relatively uniform apatite layer was formed on the multilevel structured surfaces. Moreover, the mechanism of surface mineralization can be construed as electrostatic interactions between substrates and ions. Furthermore,in vitrocell culture showed that Nb-Ta-Ti alloys had a good biocompatibility and the multilevel porous structure could enhance the cellular behaviors including: cell adhesion and spreading.

Nb-Ti-Zr alloys for orthopedic implants.

Niobium (Nb), Titanium (Ti), and Zirconium (Zr) have attracted much attention as implant materials due to it's excellent mechanical properties and biocompatibility. However, little attention has been paid to high Nb-containing biomedical alloys. Here, the 50 wt.%Nb-XTi-Zr ternary alloy(x = 20wt.%, 30 wt.%, 40 wt.%) with relative density over 90% was prepared by powder metallurgy method. The massive α(Zr) distributed along the grain boundaries and lamellar ß(Zr) appeared in the grains of ß(Nb) in the 50 wt.%Nb-20wt.%Ti-Zr alloy. The acicular α phase is mainly distributed in the ß-grain of 50 wt.%Nb-30wt.%Ti-Zr alloy. And α(Ti)-colonies in the ß-grains and continuous α(Ti)GB at ß-grain boundary can be observed in the 50 wt.%Nb-40wt.%Ti-Zr alloy. Comparing with Nb-20wt.%Ti-Zr alloy and 50 wt.%Nb-40wt.%Ti-Zr alloy, the 50 wt.%Nb-30wt.%Ti-Zr alloy showed lower Vickers hardness and elastic modulus. Furthermore, the as-sintered 50 wt.%Nb-XTi-Zr alloy promoted the cell proliferation and cell adhesion of MG-63 cells on the surface of alloys. In conclusion, the 50 wt.%Nb-XTi-Zr alloy combines excellent mechanical and biological properties, and the 50 wt.%Nb-30wt.%Ti-Zr alloy with lower elastic modulus (close to the bone) is a more promising candidate for bone implant material.

Influence of low modulus Co-Zr alloys surface modification on protein adsorption and MC3T3-E1, NIH3T3 and RAW264.7 cell behaviour.

Three types of Co-xZr (x = 5, 7.5, and 10 wt.%) were treated with hydroxyapatite (HA) and used as an object to investigate the effect of HA coating on the surface and biocompatibility of Co-xZr alloys. And the protein adsorption and the subsequent biological behaviour of osteoblast, fibroblast and macrophages were also investigated. The surface microstructure and wettability were assessed by scanning electron microscopy (SEM) and static angle profilometer. To evaluate the biocompatibility of Co-xZr and Co-xZr-HA, we quantified plasma proteins adsorption by bicinchoninic acid assay (BCA), cytotoxicity and cell proliferation by cell counting kit-8 (CCK-8) and scanning electron microscopy (SEM). The results indicated that Co-xZr-HA alloy surfaces were more hydrophilic and had higher affinity to plasma proteins. Higher protein concentrations were found adsorbed onto Co-7.5Zr-HA and Co-10Zr-HA alloys. Cytotoxicity analysis indicated that HA coating improved the biocompatibility of Co-xZr alloys. Furthermore, the comparable results of co-incubation of Co-xZr-HA alloys with cells reveal cellular attachments to HA surfaces. HA was successfully formed on Co-xZr alloys and modified the surface structure and biocompatibility of the alloys. Co-10Zr-HA and Co-7.5Zr-HA had the most favourable properties and cytocompatibility, and therefore can be potentially used for dental implants.

Evaluation of biocompatibility and osseointegration of Nb-xTi-Zr alloys for use as dental implant materials.

The aim of this study was to evaluate the biocompatibility and osteogenic potential of 50%Nb-xTi-Zr (NTZ,x= 20%, 30%, 40% by weight) alloys as compared with dental commercial pure titanium (cpTi). Cell cytotoxicity assay, fluorescence microscopy and electron microscopy were used to measure thein vitrobiocompatibility of NTZ. The expression of alkaline phosphatase (ALP), integrin ß1, osteocalcin (OC), Ki67 and collagen-I (Col-I) at the mRNA level was measured by real-time reverse transcription-polymerase chain reaction. Osseointegration ability was determined using x-ray evaluation and histological analysisin vivo. Compared with the MG63 cells grown on cpTi on day 3, the viability, adherence and proliferation rates of cells cultured on NTZ alloys were significantly improved (p< 0.05). Furthermore, similar expression levels of Ki67, Col-I, OC and ALP were found in the MG63 cells grown on NTZ alloys and those grown on cpTi. The Cbfα1 level was significantly higher for the 50%Nb-30%Ti-Zr (NTZ3) than for the cpTi group on day 6 (p< 0.01), indicating that NTZ alloys can induce osteogenesis. A considerable amount of new bone formation and osseointegration was observed around NTZ3 implants compared with cpTi implantsin vivo. Collectively, NTZ3 showed superior biocompatibility and osteogenic activity; therefore, NTZ3 may be an excellent replacement for dental Ti implants.

A hollow visible-light-responsive surface molecularly imprinted polymer for the detection of chlorpyrifos in vegetables and fruits.

A visible-light-responsive azobenzene derivative, 3,5-dichloro-4-((2,6-dichloro-4-(methacryloyloxy)phenyl)diazenyl)benzoic acid, was synthesized and used as the functional monomer to fabricate a visible-light-responsive core-shell structured surface molecularly imprinted polymer (PS-co-PMAA@VSMIP). After removal of the sacrificial PS-co-PMAA core, a hollow structured surface molecularly imprinted polymer (HVSMIP) was obtained. Both the PS-co-PMAA@VSMIP and HVSMIP were used for the detection of chlorpyrifos, a moderately toxic organophosphate pesticide. They exhibited good visible-light-responsive properties (550 nm for trans→cis and 440 nm for cis→trans isomerization for an azobenzene chromophore) in ethanol/water (9:1, v/v). Compared with the PS-co-PMAA@VSMIP, the HVSMIP had a larger surface area, pore volume, binding capacity, imprinting effect, maximum chemical binding capacity, dissociation constant, and photo-isomerization rate. The HVSMIP was applied to detect trace chlorpyrifos in fruit and vegetable samples. This was achieved by measuring the trans→cis rate constant of the HVSMIP in the sample solution, with good recoveries, low relative standard deviations, and a low detection limit.

Effects of alloying elements and annealing treatment on the microstructure and mechanical properties of Nb-Ta-Ti alloys fabricated by partial diffusion for biomedical applications.

Powder metallurgical (PM) Nb-25Ta-xTi alloys (x = 5, 15, 25, 35 at.%) were fabricated by the elemental powder sintering technology. Effects of alloying elements and annealing treatment on the microstructural evolution and mechanical properties were investigated by conducting various tests, including X-ray diffraction (XRD), scanning electron microscopy (SEM), electron probe microanalyses (EPMA), electron back scattered diffraction detector (EBSD), transmission electron microscopy (TEM) and tensile tests. The results indicated that the alloys showed a unique Nb-rich and Ta-rich dual structure due to the insufficient diffusion between powders. With the increase of Ti content, the ß phase was always retained and the alloys exhibited a relatively high density in the range of 82.4% to 90.5%. Furthermore, owing to a higher diffusion coefficient of Ti and the strengthening effect of solid solution, the volume shrinkage and tensile strength both increased along with the increase of Ti content. After the annealing treatment was introduced, the microstructure became more homogeneous and fine equiaxed grains appeared, which induced a decrease in modulus and better ductility. The Nb-25Ta-25Ti alloys exhibited a good in vitro biocompatibility due to the chemical components and the introduce of surface pores. The PM Nb-Ta-Ti alloys were promising for biomedical applications in tissue engineering after evaluated both mechanical properties and in vitro biocompatibility.

An NIR-light-responsive surface molecularly imprinted polymer for photoregulated drug release in aqueous solution through porcine tissue.

The application of photoresponsive surface molecularly imprinted polymers based on azobenzene is limited by the UV light source required and their poor water solubility. Reducing the phototoxicity and solvent toxicity of the polymers therefore presents a challenge. In this work, an NIR-light-responsive surface molecularly imprinted polymer was fabricated by atom transfer radical polymerization using up-conversion nanoparticles as the core, a hydrophilic green-light-responsive azobenzene derivative as the functional monomer, and a drug as the template. The up-conversion nanoparticles core emitted green fluorescence in the range of 520-550 nm upon NIR irradiation (980 nm, 5 W cm-2), which was absorbed by the azobenzene containing molecularly imprinted polymers layer on the up-conversion nanoparticles surface. This caused the azobenzene chromophores to undergo trans→cis isomerization in phosphate buffered solution (pH = 7.4), thus resulting in NIR-light-induced drug release. The up-conversion fluorescence spectra were used to study the interaction mechanism between the azobenzene monomer and NIR light. Compared with structural analogues of the template (antifebrin and phenacetin), the NIR-light-responsive surface molecularly imprinted polymer showed excellent specificity of recognition for the template drug (paracetamol). The maximum adsorption capacity of the NIR-light-responsive surface molecularly imprinted polymer for loading of paracetamol was 16.80 µmol g-1. The NIR-light-responsive surface molecularly imprinted polymer was applied for NIR-light-induced paracetamol release in phosphate buffered solution (pH = 7.4) through porcine tissue. This work demonstrates the potential of drug delivery systems based on molecularly imprinted polymers for application in deep tissue delivery.

In vitro cell response and in vivo primary osteointegration of highly porous Ta-Nb alloys as implant materials.

By combining the biocompatibility of Ta and excellent performance of Nb, the ß-type Ta-xNb (x = 5, 10, and 15 wt %) alloys with three-dimensional network structure was successfully fabricated. This work was designed to carry out the systematic study of in vitro/vivo biocompatibility of highly porous Ta-Nb alloys. In the present study, the in vitro biological response was characterized by cell attachment, cytotoxicity test, and gene expression. Cells were well distributed on porous alloy surface and both bulk/porous Ta-15Nb alloys showd a 0-1 RGR level. Moreover, the upregulated gene expression may reveal an increase in bone regeneration. An assessment of primary osteogenic response in vivo was achieved by histological evaluation and pull-out test. In vivo results demonstrated that the porous Ta-15Nb alloy showed a higher pull-out force than bulk Ta-15Nb alloy and exhibited a more extensive contact between implants and bones after 12 weeks. Based on the present experiments, porous Ta-Nb alloy scaffolds had a good biocompatibility and were promising for biomedical applications. © 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: 573-581, 2019.

Microstructure, mechanical properties, and preliminary biocompatibility evaluation of binary Ti-Zr alloys for dental application.

The microstructure, mechanical properties, and in vitro biocompatibility of vacuum-sintered Ti-xZr binary alloys (x = 5, 15, 25, 35, 45 wt%) were investigated. The results indicated that α and α' phase existed in Ti-xZr alloys. The hardness of the Ti-Zr alloys increased as the contents increased and ranged from 473 HV (Ti-5Zr) to 525 HV (Ti-45Zr). Increasing Zr content could lead to an increase in compressive and bending strength. Additionally, the Ti-45Zr alloy exhibited the maximum bending strength of 867.1 MPa and the maximum compressive strength of 1599.8 MPa which were much larger than that of CP-Ti. Moreover, all Ti-Zr alloys showed a lower elastic modulus (ranging from 53.5 to 59.3 GPa) compared with CP-Ti (103 GPa). The in vitro cytotoxicity tests were carried out for biocompatibility evaluation. The alloys presented no cytotoxic effects and the surface of the alloys exhibited great growth conditions for MG-63 cells. The Ti-45Zr alloy exhibited better mechanical properties and biocompatibility. In conclusion, Ti-45Zr alloy is of great potential for dental applications.

Porous Nb-Ti-Ta alloy scaffolds for bone tissue engineering: Fabrication, mechanical properties and in vitro/vivo biocompatibility.

Porous Nb-Ti-Ta (at.%) alloys with the pore size of 100-600µm and the porosity of 50%-80% were fabricated by the combination of the sponge impregnation technique and sintering method. The results revealed that the pores were well connected with three-dimensional (3D) network structure, which showed morphological similarity to the anisotropic porous structure of human bones. The results also showed that the alloys could provide the compressive Young's modulus of 0.11±0.01GPa to 2.08±0.09GPa and the strength of 17.45±2.76MPa to 121.67±1.76MPa at different level of porosity, indicating that the mechanical properties of the alloys are similar to those of human bones. Pore structure on the compressive properties was also discussed on the basis of the deformation mode. The relationship between compressive properties and porosity was well consistent with the Gibson-Ashby model. The mechanical properties could be tailored to match different requirements of the human bones. Moreover, the alloys had good biocompatibility due to the porous structure with higher surface, which were suitable for apatite formation and cell adhesion. In conclusion, the porous Nb-Ti-Ta alloy is potentially useful in the hard tissue implants for the appropriate mechanical properties as well as the good biocompatible properties.

Microstructure, mechanical behavior and biocompatibility of powder metallurgy Nb-Ti-Ta alloys as biomedical material.

Microstructures, mechanical properties, apatite-forming ability and in vitro experiments were studied for Nb-25Ti-xTa (x=10, 15, 20, 25, 35at.%) alloys fabricated by powder metallurgy. It is confirmed that the alloys could achieve a relative density over 80%. Meanwhile, the increase in Ta content enhances the tensile strength, elastic modulus and hardness of the as-sintered alloys. When increasing the sintering temperatures, the microstructure became more homogeneous for ß phase, resulting in a decrease in the modulus and strength. Moreover, the alloys showed a good biocompatibility due to the absence of cytotoxic elements, and were suitable for apatite formation and cell adhesion. In conclusion, Nb-25Ti-xTa alloys are potentially useful in biomedical applications with their mechanical and biological properties being evaluated in this work.

Fabrication, characterization and in vitro biocompatibility evaluation of porous Ta-Nb alloy for bone tissue engineering.

Porous Ta-Nb alloys were fabricated using the sponge impregnation technique and the powder metallurgy technique (P/M) in combination. All porous Ta-Nb alloys displayed interconnected open cell structures with porosities around 64% and pore sizes in the range of 300-500 µm. No carbide, oxide, or intermetallic-related phases were detected by the X-ray diffraction (XRD). Porous Ta-Nb alloys displayed sintering neck growth, smoother surface of the particles and more shrinkage of the micropores, with Nb contents increasing from 5% to 15%. The compressive strength and Young's modulus of the Ta-Nb alloys agreed well with the requirements of trabecular bone. The normalized compressive plateau stress and Young's modulus increased from 52.27 MPa to 85.43 MPa and from 1.850 GPa to 2.540 GPa, respectively, with Nb contents increasing from 5% to 15%. Porous Ta-Nb alloys had no cytotoxicity and possessed the excellent biocompatibility similar to porous Ta scaffolds.