In vitro bio-functional performances of the novel superelastic beta-type Ti–23Nb–0.7Ta–2Zr–0.5N alloy

An in vivo toxicity assessment of piezoelectric sodium potassium niobate [NaxK1-xNbO3 (x = 0.2-0.8)] nanoparticulates towards bone tissue engineering approach

One of the recent challenges in the design/development of prosthetic orthopedic implants is to address the concern of local/systemic toxicity of debris particles, released due to wear or degradation. Such debris particles often lead to inflammation at the implanted site or aseptic loosening of the prosthesis which results in failure of the implant during long run. Several in vitro studies demonstrated the potentiality of piezoelectric sodium potassium niobate [Na_xK_1-xNbO₃ (x = 0.2, 0.5, 0.8), NKN] as an emerging next-generation polarizable orthopedic implant. In this perspective, we performed an in vivo study to examine the local and systemic toxicity of NKN nanoparticulates, as a first report. In the present study, male Wistar rats were intra-articularly injected to the knee joint with 100 μl of NKN nanoparticulates (25 mg/ml in normal saline). After 7 days of exposure, the histopathological analyses demonstrate the absence of any inflammation or dissemination of nanoparticulates in vital organs such as heart, liver, kidney and spleen. The anti-inflammatory cytokines (IL-4 and IL-10) profile analyses suggest the increased anti-inflammatory response in the treated rats as compared to non-injected (control) rats, preferably for the sodium and potassium rich NKN i.e., Na_0.8K_0.2NbO₃ and Na_0.2K_0.8NbO₃. The biochemical analyses revealed no pathological changes in the liver and kidney of particulate treated rats. The present study is the first proof to confirm the non-toxic nature of NKN nanoparticulates which provides a step forward towards the development of prosthetic orthopedic implants using biocompatible piezoelectric NKN ceramics.

Microstructural Evolution, Mechanical Properties, and Preosteoblast Cell Response of a Post-Processing-Treated TNT5Zr β Ti Alloy Manufactured via Selective Laser Melting

A Ti–34Nb–13Ta–5Zr (TNT5Zr) β Ti alloy with a high strength-to-modulus ratio has been developed, showing its potential to become another candidate material in load-bearing implant applications. This work mainly investigates the microstructural evolution, mechanical properties, and biocompatibility of a post-processing-treated TNT5Zr alloy manufactured via selective laser melting (SLM). Transmission electron microscopy observation shows the existence of the single beta grain matrix and alpha precipitates along the grain boundary in the SLM + HIP manufactured TNT5Zr alloy (TNT5Zr-AF + HIP), and ellipsoidal nano-sized intragranular α″ precipitates (approx. 5–10 nm) were introduced after the subsequent low-temperature aging treatment. The precipitation strengthening enables the SLM + HIP + aging manufactured TNT5Zr (TNT5Zr-AF + HIPA) alloy to show a comparable ultimate tensile strength (853 ± 9 MPa) to that of the reference material (Ti64-AF + HIP, 926 ± 23 MPa). Including the inferior notch-like surface of the test pieces, the slip-band cracking that occurs in this ductile TNT5Zr-AF + HIPA alloy is regarded as the main factor in determining its fatigue strength (170 MPa). In vitro short-term biocompatibility evaluation reveals almost no significant difference in the preosteoblast viability, differentiation, and mineralization between TNT5Zr-AF + HIPA and the reference biomaterial (Ti64-AF + HIP).

In-silico design and experimental validation of TiNbTaZrMoSn to assess accuracy of mechanical and biocompatibility predictive models

Numerical design of TiNbTaZrMoSn alloy preceded its manufacture and mechanical, physico-chemical and in vitro characterisation. The specifications of the alloy required a multi-objective optimisation including lower modulus of elasticity than c.p.Ti, high strength, stabilised β crystal structure with a low martensitic start temperature, a narrow solidification range and high biocompatibility. The results reveal that there was a good match between the bulk mechanical properties exhibited by the alloy experimentally and those predicted. Regarding surface properties, independent of roughness effects, the oxide thickness and surface zeta-potential, measured in biologically relevant electrolytes and at physiological pH, arose as important factors in osteoblastic activity (i.e., cell proliferation, measured via DNA, protein and metabolite content, and differentiation, via ALP levels), but not in cell adhesion and viability. The thinner oxide layer and lower absolute value of surface zeta-potential on the TiNbTaZrMoSn alloy explain its lesser osteogenic properties (i.e., inhibition of ALP activity) compared to the c.p. Ti. This study demonstrates that the numerical models to predict microstructure and bulk mechanical properties of β-Ti alloys are robust, but that the prediction of cellular bioactivity lags behind and still requires parameterisation to account for features such as oxide layer composition and thickness, electro-chemical properties and surface charge, and topography to optimise cell response in silico before committing to the costly manufacture and deployment of these alloys in regenerative medicine.

The Influence of Severe Plastic Deformation on Microstructure and In Vitro Biocompatibility of the New Ti-Nb-Zr-Ta-Fe-O Alloy Composition

In this work, severe plastic deformation (SPD) of the newly designed Ti-Nb-Zr-Ta-Fe-O GUM metal was successfully conducted at room temperature using high speed high pressure torsion (HSHPT) followed by cold rolling (CR) to exploit the suitability of the processed alloy for bone staples. The Ti-31.5Nb-3.1Zr-3.1Ta-0.9Fe-0.16O GUM alloy was fabricated in a levitation melting furnace using a cold crucible and argon protective atmosphere. The as-cast specimens were subjected to SPD, specifically HSHPT, and then processed by the CR method to take the advantages of both grain refinement and larger dimensions. This approach creates the opportunity to obtain temporary orthopedic implants nanostructured by SPD. The changes induced by HSHPT technology from the coarse dendrite directly into the ultrafine grained structure were examined by optical microscopy, scanning electron microscopy and X-ray diffraction. The structural investigations showed that by increasing the deformation, a high density of grain boundaries is accumulated, leading gradually to fine grain size. In addition, the in vitro biocompatibility studies were conducted in parallel on the GUM alloy specimens in the as-cast state, and after HSHPT- and HSHPT+CR- processing. For comparative purposes, in vitro behavior of the bone-derived MC3T3-E1 cells on the commercially pure titanium has also been investigated regarding the viability and proliferation, morphology and osteogenic differentiation. The results obtained support the appropriateness of the HSHPT technology for developing compression staples able to ensure a better fixation of bone fragments.

Physiochemical and biological evaluation of SLM-manufactured Ti-10Ta-2Nb-2Zr alloy for biomedical implant applications

Titanium alloys, such as Ti-10Ta-2Nb-2Zr (TTNZ), are promising biomaterials due to their excellent biocompatibility and low Young's modulus. The TTNZ samples herein were manufactured by selective laser melting and the novel material was evaluated as a dental implant in vitro and in vivo. The microstructure, mechanical properties, electrochemical behaviour, cytotoxicity, haemocompatibility and osteogenic differentiation were systematically investigated. Based on the tensile test results, the as-printed TTNZ samples had an elongation of 20.23% ± 1.95%, an ultimate tensile strength of 646.61 ± 24.96 MPa and a Young's modulus of 23.72 ± 1.18 GPa. According to the biocompatible value, the as-printed TTNZ sample exhibited no cell cytotoxicity and it showed even better cell adhesion ability than that of the as-printed Ti-6Al-4 V and wrought Ti-6Al-4 V samples. The haemolysis percentage of the as-printed TTNZ sample was 0.629% ± 0.363%. Moreover, the as-printed TTNZ sample facilitated protein adsorption and osteogenic differentiation of human osteoblast-like (MG-63) cells in vitro. The in vivo data also demonstrated the histocompatibility of the as-printed TTNZ. In summary, the as-printed TTNZ developed in this study demonstrated good biocompatibility, low stress shielding, excellent ductility and great osteogenic differentiation. These results indicated that as-printed TTNZ alloys can be promising for end-use human biomedical applications.

The effect of nano-size second precipitates on the structure, apatite-inducing ability and in-vitro biocompatibility of Ti-29Nb-14Ta-4.5Zr alloy

The apatite formation and in-vitro biocompatibility of Ti-29Nb-14Ta-4.5Zr (TNTZ) alloy reinforced by various nano-sized phases of α″, α, and ω in the β matrix have been studied. The electrochemical performances of the elaborated microstructures have been assessed through potentiodynamic polarization in the simulated body fluid (SBF) and interestingly, the β + ω specimen exhibited an extraordinary corrosion resistance compared to the others. This was attributed to the uniform distribution, spherical morphology and coherent interface of the ω nano-precipitates. The polarization tests in simulated body fluid showed the high tendency of apatite formation on the surface of the β- matrix contained ω precipitates. The in-vitro cytotoxicity analysis employing MTT (3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide) assay showed >85% cell viability of the TNTZ alloy reinforced by nano-ω precipitations. Since this specimen showed the highest cell adhesion as well, it introduces this structure as a promising high potential candidate for biomedical applications due to its high corrosion resistance, biocompatibility, ultra-low cytotoxicity, and good cell adhesion.

Enhanced Bone Remodeling Effects of Low-Modulus Ti-5Zr-3Sn-5Mo-25Nb Alloy Implanted in the Mandible of Beagle Dogs under Delayed Loading

Titanium (Ti) and its alloys are widely used in the dental and prosthetic implant fields due to their favorable biocompatibility. In this study, porous surface coatings incorporated with nanoscale hydroxyapatite particles on the surface of Ti and Ti-5Zr-3Sn-5Mo-25Nb (TLM) alloy were fabricated by microarc oxidation followed by hydrothermal treatment; the surface roughness and hydrophilicity were obviously enhanced by the surface modification procedure. In vivo, four adult male beagle dogs were selected for an implantation procedure and restored with full metal crowns after healing for 3 months. The bone responses were evaluated via histomorphological observation. Raman spectral analysis and nanoindentation experiments were used to quantitatively and qualitatively estimate the characteristics of the bone formed around the implants. Compared to the Ti group, the TLM titanium alloy group showed a significant increase in the percentage of bone-implant interface contact, bone inside the thread, mineralization, crystallinity, modulus of elasticity, and hardness of the integrated bone after delayed loading in the TLM group. Therefore, the TLM titanium alloy is considered a candidate implant material with desirable biomechanical compatibility, especially under applied stress.

Corrosion behavior, in vitro and in vivo biocompatibility of a newly developed Ti-16Nb-3Mo-1Sn superelastic alloy

The biocompatibility of a recently developed Ni-free Ti-16Nb-3Mo-1Sn (at.%) superelastic alloy was investigated both in vitro and in vivo. In addition, static water contact angle (WCA) and electrochemical tests were carried out. Commercial purity Ti (cp-Ti), which is already being used as a clinical material, was used as the control material. The alloy showed a stable corrosion behavior similar to that of the cp-Ti. The WCA measurements showed that the alloy exhibited hydrophilic properties that contributed to cell attachment to implants, as evident by the cytocompatibility tests. According to the in vivo implantation tests conducted on 30 adult BALB/c rats for periods up to 12 weeks, the tissue reaction around the implants was similar for both the cp-Ti and the alloy, and no significant difference was found in almost all parameters analyzed. Due to its stable superelastic properties accompanied with excellent biocompatibility and high corrosion resistance, we believe that this alloy is considered as a promising substitute for the biomedical materials containing Ni or other toxic elements.

Nanochannelar Topography Positively Modulates Osteoblast Differentiation and Inhibits Osteoclastogenesis

Based on previously reported findings showing reduced foreign body reactions on nanochannelar topography formed on TiZr alloy, this study explores the in vitro effects of such a nanostructured surface on cells relevant for implant osseointegration, namely osteoblasts and osteoclasts. We show that such nanochannelar surfaces sustain adhesion and proliferation of mouse pre-osteoblast MC3T3-E1 cells and enhance their osteogenic differentiation. Moreover, this specific nanotopography inhibits nuclear factor kappa-B ligand (RANKL)-mediated osteoclastogenesis. The nanochannels’ dual mode of action on the bone-derived cells could contribute to an enhanced bone formation around the bone implants. Therefore, these results warrant further investigation for nanochannels’ use as surface coatings of medical implant materials.

Characterization and In Vitro and In Vivo Assessment of a Novel Cellulose Acetate-Coated Mg-Based Alloy for Orthopedic Applications

Despite their good biocompatibility and adequate mechanical behavior, the main limitation of Mg alloys might be their high degradation rates in a physiological environment. In this study, a novel Mg-based alloy exhibiting an elastic modulus E = 42 GPa, Mg-1Ca-0.2Mn-0.6Zr, was synthesized and thermo-mechanically processed. In order to improve its performance as a temporary bone implant, a coating based on cellulose acetate (CA) was realized by using the dipping method. The formation of the polymer coating was demonstrated by FT-IR, XPS, SEM and corrosion behavior comparative analyses of both uncoated and CA-coated alloys. The potentiodynamic polarization test revealed that the CA coating significantly improved the corrosion resistance of the Mg alloy. Using a series of in vitro and in vivo experiments, the biocompatibility of both groups of biomaterials was assessed. In vitro experiments demonstrated that the media containing their extracts showed good cytocompatibility on MC3T3-E1 pre-osteoblasts in terms of cell adhesion and spreading, viability, proliferation and osteogenic differentiation. In vivo studies conducted in rats revealed that the intramedullary coated implant for fixation of femur fracture was more efficient in inducing bone regeneration than the uncoated one. In this manner, the present study suggests that the CA-coated Mg-based alloy holds promise for orthopedic aplications.

Osseointegration behavior of novel Ti-Nb-Zr-Ta-Si alloy for dental implants: an in vivo study

This study aimed to evaluate the effects of Ti-Nb-Zr-Ta-Si alloy implants on mineral apposition rate and new BIC contact in rabbits. Twelve Ti-Nb-Zr-Ta-Si alloy implants were fabricated and placed into the right femur sites in six rabbits, and commercially pure titanium implants were used as controls in the left femur. Tetracycline and alizarin red were administered 3 weeks and 1 week before euthanization, respectively. At 4 weeks and 8 weeks after implantation, animals were euthanized, respectively. Surface characterization and implant-bone contact surface analysis were performed by using a scanning electron microscope and an energy dispersive X-ray detector. Mineral apposition rate was evaluated using a confocal laser scanning microscope. Toluidine blue staining was performed on undecalcified sections for histology and histomorphology evaluation. Scanning electron microscope and histomorphology observation revealed a direct contact between implants and bone of all groups. After a healing period of 4 weeks, Ti-Nb-Zr-Ta-Si alloy implants showed significantly higher mineral apposition rate compared to commercially pure titanium implants (P < 0.05), whereas there was no significant difference between Ti-Nb-Zr-Ta-Si alloy implants and commercially pure titanium implants (P > 0.05) at 8 weeks. No significant difference of bone-to-implant contact was observed between Ti-Nb-Zr-Ta-Si alloy implants and commercially pure titanium implants implants after a healing period of 4 weeks and 8 weeks. This study showed that Ti-Nb-Zr-Ta-Si alloy implants could establish a close direct contact comparedto commercially pure titanium implants implants, improved mineral matrix apposition rate, and may someday be an alternative as a material for dental implants.

Biological Behaviour and Enhanced Anticorrosive Performance of the Nitrided Superelastic Ti-23Nb-0.7Ta-2Zr-0.5N Alloy

The influence of gas nitriding surface treatment on the superelastic Ti-23Nb-0.7Ta-2Zr-0.5N alloy was evaluated. A thorough characterization of bare and nitrided Ti-based alloy and pure Ti was performed in terms of surface film composition and morphology, electrochemical behaviour, and short term osteoblast response. XPS analysis showed that the nitriding treatment strongly influenced the composition (nitrides and oxynitrides) and surface properties both of the substrate and of the bulk alloy. SEM images revealed that the nitrided surface appears as a similar dotted pattern caused by the formation of N-rich domains coexisting with less nitrided domains, while before treatment only topographical features could be observed. All the electrochemical results confirmed the high chemical stability of the nitride and oxynitride coating and the superiority of the applied treatment. The values of the corrosion parameters ascertained the excellent corrosion resistance of the coated alloy in the real functional conditions from the human body. Cell culture experiments with MG63 osteoblasts demonstrated that the studied biomaterials do not elicit any toxic effects and support cell adhesion and enhanced cell proliferation. Altogether, these data indicate that the nitrided Ti-23Nb-0.7Ta-2Zr-0.5N alloy is the most suitable substrate for application in bone implantology.

Superelasticity, corrosion resistance and biocompatibility of the Ti-19Zr-10Nb-1Fe alloy

Microstructure, mechanical properties, superelasticity and biocompatibility of a Ti-19Zr-10Nb-1Fe alloy are investigated. X-ray diffraction spectroscopy and transmission electron microscopy observations show that the as-cast Ti-19Zr-10Nb-1Fe alloy is composed of α' and β phases, but only the β phase exists in the as-rolled and as-quenched alloys. The tensile stress-strain tests indicate that the as-quenched alloy exhibits a good combination of mechanical properties with a large elongation of 25%, a low Young's modulus of 59 GPa and a high ultimate tensile stress of 723 MPa. Superelastic recovery behavior is found in the as-quenched alloy during tensile tests, and the corresponding maximum of superelastic strain is 4.7% at the pre-strain of 6%. A superelastic recovery of 4% with high stability is achieved after 10 cyclic loading-unloading training processes. Potentiodynamic polarization and ion release measurements indicate that the as-quenched alloy shows a lower corrosion rate in Hank's solution and a much less ion release rate in 0.9% NaCl solution than those of the NiTi alloys. Cell culture results indicate that the osteoblasts' adhesion and proliferation are similar on both the Ti-19Zr-10Nb-1Fe and NiTi alloys. A better hemocompatibility is confirmed for the as-quenched Ti-19Zr-10Nb-1Fe alloy, attributed to more stable platelet adhesion and small activation degree, and a much lower hemolysis rate compared with the NiTi alloy.

Hydroxyapatite coatings with oriented nanoplate arrays: synthesis, formation mechanism and cytocompatibility

A novel strategy has been developed to fabricate hydroxyapatite coatings with oriented nanoplate arrays for implants of human hard tissues.

In vitro performance assessment of new beta Ti-Mo-Nb alloy compositions

New β-titanium based alloys with low Young's modulus are currently required for the next generation of metallic implant materials to ensure good mechanical compatibility with bone. Several of these are representatives of the ternary Ti-Mo-Nb system. The aim of this paper is to assess the in vitro biological performance of five new low modulus alloy compositions, namely Ti12Mo, Ti4Mo32Nb, Ti6Mo24Nb, Ti8Mo16Nb and Ti10Mo8Nb. Commercially pure titanium (cpTi) was used as a reference material. Comparative studies of cell activity exhibited by MC3T3-E1 pre-osteoblasts over short- and long-term culture periods demonstrated that these newly-developed metallic substrates exhibited an increased biocompatibility in terms of osteoblast proliferation, collagen production and extracellular matrix mineralization. Furthermore, all analyzed biomaterials elicited an almost identical cell response. Considering that macrophages play a pivotal role in bone remodeling, the behavior of a monocyte-macrophage cell line, RAW 264.7, was also investigated showing a slightly lower inflammatory response to Ti-Mo-Nb biomaterials as compared with cpTi. Thus, the biological performances together with the superior mechanical properties recommend these alloys for bone implant applications.