In vitro cytotoxicity and hemocompatibility studies of Ti-Nb, Ti-Nb-Zr and Ti-Nb-Hf biomedical shape memory alloys

Surface modification of the laser powder bed-fused Ti-Zr-Nb scaffolds by dynamic chemical etching and Ag nanoparticles decoration

Metallic lattice scaffolds are designed to mimic the architecture and mechanical properties of bone tissue and their surface compatibility is of primary importance. This study presents a novel surface modification protocol for metallic lattice scaffolds printed from a superelastic Ti-Zr-Nb alloy. This protocol consists of dynamic chemical etching (DCE) followed by silver nanoparticles (AgNP) decoration. DCE, using an 1HF + 3HNO3 + 12H2O23% based solution, was used to remove partially-fused particles from the surfaces of different as-built lattice structures (rhombic dodecahedron, sheet gyroid, and Voronoi polyhedra). Subsequently, an antibacterial coating was synthesized on the surface of the scaffolds by a controlled (20 min at a fixed volume flowrate of 500 mL/min) pumping of the functionalization solutions (NaBH4 (2 mg/mL) and AgNO3 (1 mg/mL)) through the porous structures. Following these treatments, the scaffolds' surfaces were found to be densely populated with Ag nanoparticles and their agglomerates, and manifested an excellent antibacterial effect (Ag ion release rate of 4-8 ppm) suppressing the growth of both E. coli and B. subtilis bacteria up to 99 %. The scaffold extracts showed no cytotoxicity and did not affect cell proliferation, indicating their safety for subsequent use as implants. A cytocompatibility assessment using MG-63 spheroids demonstrated good attachment, spreading, and active migration of cells on the scaffold surface (over 96 % of living cells), confirming their biotolerance. These findings suggest the promise of this surface modification approach for developing superelastic Ti-Zr-Nb scaffolds with superior antibacterial properties and biocompatibility, making them highly suitable for bone implant applications.

Promoted mechanical properties and functionalities via Ta-tailored Ti-Au-Cr shape memory alloys towards biomedical applications

In view of the urgent demands of shape memory alloys (SMAs) for biomedical applications due to the world population aging issue, the mechanical properties and functionalities of the biocompatible Ti-Au-Cr-based SMAs, which are tailored by Ta additions, have been developed in this study. The quaternary SMAs were successfully manufactured by physical metallurgy techniques and their mechanical properties and functionalities were examined. In the continuous tensile tests, it was found that the correlation between the yielding strength and phase stability followed a typical trend of mechanical behavior of SMAs, showing the lowest yielding strength at the metastable β-parent phase. Functional mappings between the alloy strength and elongation revealed that compared to the Ta-free specimen, the ductility was promoted 50% while the strength remained intact through the 4 at.% introduction of Ta. Slight shape recovery was observed in the cyclic loading-unloading tensile tests during the unloading process and the highest shape recovery was found in the Ti-4 at.% Au-5 at.% Cr-4 at.% Ta specimen. This indicates that the 4 at.% Ta tailored Ti-Au-Cr SMAs could be a promising material for biomedical applications.

Mixed oxide nanotubes in nanomedicine: A dead-end or a bridge to the future?

Nanomedicine has seen a significant rise in the development of new research tools and clinically functional devices. In this regard, significant advances and new commercial applications are expected in the pharmaceutical and orthopedic industries. For advanced orthopedic implant technologies, appropriate nanoscale surface modifications are highly effective strategies and are widely studied in the literature for improving implant performance. It is well-established that implants with nanotubular surfaces show a drastic improvement in new bone creation and gene expression compared to implants without nanotopography. Nevertheless, the scientific and clinical understanding of mixed oxide nanotubes (MONs) and their potential applications, especially in biomedical applications are still in the early stages of development. This review aims to establish a credible platform for the current and future roles of MONs in nanomedicine, particularly in advanced orthopedic implants. We first introduce the concept of MONs and then discuss the preparation strategies. This is followed by a review of the recent advancement of MONs in biomedical applications, including mineralization abilities, biocompatibility, antibacterial activity, cell culture, and animal testing, as well as clinical possibilities. To conclude, we propose that the combination of nanotubular surface modification with incorporating sensor allows clinicians to precisely record patient data as a critical contributor to evidence-based medicine.

Ultrafine-Grained Ti-31Mo-Type Composites with HA and Ag, Ta2O5 or CeO2 Addition for Implant Applications

Ultrafine-grained Ti31Mo alloy and Ti31Mo5HA, Ti31Mo5HA-Ag (or Ta₂O₅, CeO₂) composites with a grain size of approximately 2 μm were produced by the application of mechanical alloying and powder metallurgy. Additionally, the surface of the Ti31Mo alloy was modified. In the first stage, the specimens were immersed in 5M NaOH for 24 h at 60 °C. In the second stage, hydroxyapatite (HA) was deposited on the sample surface. The cathodic deposition at −5 V vs. open circuit potential (OCP) in the electrolyte containing 0.25M CaNa₂-EDTA (di-calcium ethylenediaminetetraacetic acid), 0.25M K₂HPO₄ in 1M NaOH at 120 °C for 2 h was applied. The bulk Ti31Mo alloy is a single β-type phase. In the alkali-modified surface titanium oxide, Ti₃O is formed. After hydrothermal treatment, the surface layer mostly consists of the Ca₁₀(PO₄)₆(OH)₂ (81.23%) with about 19% content of CaHPO₄·2H₂O. Using optical profiler, roughness 2D surface topography parameters were estimated. The in vitro cytocompatibility of synthesized materials was studied. The cell lines of normal human osteoblasts (NHost) and human periodontal ligament fibroblasts (HPdLF) was conducted in the presence of tested biomaterials. Ultrafine-grained Ti-based composites altered with HA and Ag, Ta₂O₅ or CeO₂ have superior biocompatibility than the microcrystalline Ti metal. NHost and HPdLF cells in the contact with the synthesized biomaterial showed stable proliferation activity. Biocompatibility tests carried out indicate that the ultrafine-grained Ti31Mo5HA composites with Ag, Ta₂O_5, or CeO₂ could be a good candidate for implant applications.

Composite and Surface Functionalization of Ultrafine-Grained Ti23Zr25Nb Alloy for Medical Applications

In this study, the ultrafine-grained Ti23Zr25Nb-based composites with 45S5 Bioglass and Ag, Cu, or Zn additions were produced by application of the mechanical alloying technique. Additionally, the base Ti23Zr25Nb alloy was electrochemically modified in the two stages of processing: electrochemical etching in the solution of H₃PO₄ and HF followed by electrochemical deposition in Ca(NO₃)₂, (NH₄)₂HPO₄, and HCl. The in vitro cytocompatibility studies were also done with comparison to the commercially pure titanium. The established cell lines of Normal Human Osteoblasts (NHost, CC-2538) and Human Periodontal Ligament Fibroblasts (HPdLF, CC-7049) were used. The culture was conducted among the tested materials. Ultrafine-grained titanium-based composites modified with 45S5 Bioglass and Ag, Cu, or Zn metals have higher biocompatibility than the reference material in the form of a microcrystalline Ti. Proliferation activity was at a stable level with contact with studied materials. In vitro evaluation research showed that the ultrafine-grained Ti23Zr25Nb-based composites with 45S5 Bioglass and Ag, Cu, or Zn additions, with a Young modulus below 50 GPa, can be further used in the biomedical field.

Novel Biocompatible Zr-Based Alloy with Low Young's Modulus and Magnetic Susceptibility for Biomedical Implants

The microstructure, mechanical properties, magnetic susceptibility, electrochemical corrosion performance, in vitro cell compatibility and blood consistency of Zr-16Nb-xTi (x = 0, 4, 8, 12 and 16 wt.%) materials were investigated as potential materials for biomedical implants. X-ray diffraction (XRD) and Transmission electron microscopy (TEM) analyses revealed the secondary phase martensite α' formed during the quenching process. The phase composition contained metastable β and martensite α', resulting from Ti addition. These phase constitutions were the main causes of a low Young's modulus and magnetic susceptibility. The in vitro cytocompatibility analysis illustrated that the MG63 cells maintained high activity (from 91% to 97%) after culturing in Zr-16Nb-xTi extraction media for 12 days due to the high internal biocompatibility of Zr, Nb and Ti elements, as well as the optimal corrosion resistance of Zr-16Nb-xTi. On the basis of Inductively coupled plasma optical emission spectrometry (ICP-OES) ion release studies, the concentration of Zr, Nb and Ti was noted to reach the equipment detective limit of 0.001 mg/L, which was much lower than pure Ti. With respect to the corrosion behavior in Hank's solution, Zr-16Nb-16Ti displayed superior properties, possessing the lowest corrosion current density and widest passivation region, attributed to the addition of Ti. The blood compatibility test illustrated that the Zr-16Nb-xTi materials were nonhemolytic, and the platelets maintained a spherical shape, with no aggregation or activation on Zr-16Nb-xTi. Overall, Ti addition has obvious effects on the developed Zr-16Nb-xTi alloys, and Zr-16Nb-4Ti exhibited low magnetic susceptibility, low modulus, good biocompatibility and proper corrosion properties, demonstrating the potential of use as implant biomaterials.

Comparison of Ti-35Nb-7Zr-5Ta and Ti-6Al-4V hydrofluoric acid/magnesium-doped surfaces obtained by anodizing

OBJECTIVES

Development of a new generation of stable β alloy, free of aluminum or vanadium and with better biological and mechanical compatibility and evaluate the surface properties of Ti-6Al-4V and Ti-35Nb-7Zr-5Ta after anodization in hydrofluoric acid, followed by deposition of different electrolyte concentrations of magnesium particles by micro arc-oxidation treatment.

METHODS

Disks were anodized in hydrofluoric acid. After this first anodization, the specimens received the deposition of magnesium using different concentration (8.5% and 12.5%) and times (30s and 60s). The surface morphology was assessed using scanning electron microscopy, and the chemical composition was assessed using energy dispersive x ray spectroscopy. The surface free energy was measured from the contact angle, and the mean roughness was measured using a digital profilometer.

RESULTS

Anodization in hydrofluoric acid provided the formation of nanotubes in both alloys, and the best concentration of magnesium considered was 8.5%, as it was the condition where the magnesium was incorporated without covering the morphology of the nanotubes. X-ray dispersive energy spectroscopy showed magnesium incorporation in all conditions. The average roughness was increased in the Ti-35Nb-7Zr-5Ta alloy.

CONCLUSIONS

It was concluded that anodizing could be used to deposit magnesium on the surfaces of Ti-6Al-4V and Ti-35Nb-7Zr-5Ta nanotubes, with better results obtained in samples with magnesium concentration in 8.5% and the process favored the roughness in the Ti-35Nb-7Zr-5Ta group.

Superelastic Behavior of Ti-Nb Alloys Obtained by the Laser Engineered Net Shaping (LENS) Technique

The effect of Nb content on microstructure, mechanical properties and superelasticity was investigated for a series of Ti-xNb alloys, fabricated by the laser engineered net shaping method, using elemental Ti and Nb powders. The microstructure of as-deposited materials consisted of columnar β-phase grains, elongated in the built direction. However, due to the presence of undissolved Nb particles during the deposition process, an additional heat treatment was necessary. The observed changes in mechanical properties were explained in relation to the phase constituents and deformation mechanisms. Due to the elevated oxygen content in the investigated materials (2 at.%), the specific deformation mechanisms were observed at lower Nb content in comparison to the conventionally fabricated materials. This made it possible to conclude that oxygen increases the stability of the β phase in β–Ti alloys. For the first time, superelasticity was observed in Ti–Nb-based alloys fabricated by the additive manufacturing method. The highest recoverable strain of 3% was observed in Ti–19Nb alloy as a result of high elasticity and reverse martensitic transformation stress-induced during the loading.

Design and fabrication of Ti-Zr-Hf-Cr-Mo and Ti-Zr-Hf-Co-Cr-Mo high-entropy alloys as metallic biomaterials

Novel TiZrHfCr_0.2Mo and TiZrHfCo_0.07Cr_0.07Mo high-entropy alloys for metallic biomaterials (bio-HEAs) were developed based on the combination of Ti-Nb-Ta-Zr-Mo alloy system and Co-Cr-Mo alloy system as commercially-used metallic biomaterials. Ti-Zr-Hf-Cr-Mo and Ti-Zr-Hf-Co-Cr-Mo bio-HEAs were designed using (a) a tree-like diagram for alloy development, (b) empirical alloy parameters for solid-solution-phase formation, and (c) thermodynamic calculations focused on solidification. The newly-developed bio-HEAs overcomes the limitation of classical metallic biomaterials by the improvement of (i) mechanical hardness and (ii) biocompatibility all together. The TiZrHfCr_0.2Mo and TiZrHfCo_0.07Cr_0.07Mo bio-HEAs showed superior biocompatibility comparable to that of commercial-purity Ti. The superior biocompatibility, high mechanical hardness and low liquidus temperature for the material processing in TiZrHfCr_0.2Mo and TiZrHfCo_0.07Cr_0.07Mo bio-HEAs compared with the Ti-Nb-Ta-Zr-Mo bio-HEAs gave the authenticity of the application of bio-HEAs for orthopedic implants with multiple functions.

Anodic formation and biomedical properties of hafnium-oxide nanofilms

Hafnium dioxide (HfO₂) is attracting attention for bio-related applications due to its good cytocompatibility, high density, and resistance to corrosion and mechanical damage. Here we synthesize two types of hafnium-oxide thin films on substrates via self-organized electrochemical anodization: (1) an array of hierarchically structured nanorods anchored to a thin oxide layer and (2) a microscopically flat oxide film. The nanostructured film is composed of a unique mixture of HfO₂, suboxide Hf₂O₃, and oxide-hydroxide compound HfO₂·nH₂O whereas the flat film is mainly HfO₂. In vitro interaction of the two films with MG-63 osteoblast-like cells and Gram-negative E. coli bacteria is studied for the first time to assess the potential of the films for biomedical application. Both films reveal good cytocompatibility and affinity for proteins, represented by fibronectin and especially albumin, which is absorbed in a nine times larger amount. The morphology and specific surface chemistry of the nanostructured film cause a two-fold enhanced antibacterial effect, better cell attachment, significantly improved proliferation of cells, five-fold rise in the cellular Young's modulus, slightly stronger production of reactive oxygen species, and formation of cell clusters. Compared with the flat film, the nanostructured one features the weakening of AFM-measured adhesion force at the cell/surface interface, probably caused by partially lifting the nanorods from the substrate due to the strong contact with cells. The present findings deepen the understanding of biological processes at the living cell/metal-oxide interface, underlying the role of surface chemistry and the impact of nanostructuring at the nanoscale.

The Mechanical Properties and In Vitro Biocompatibility of PM-Fabricated Ti-28Nb-35.4Zr Alloy for Orthopedic Implant Applications

A biocompatible Ti-28Nb-35.4Zr alloy used as bone implant was fabricated through the powder metallurgy process. The effects of mechanical milling and sintering temperatures on the microstructure and mechanical properties were investigated systematically, before in vitro biocompatibility of full dense Ti-28Nb-35.4Zr alloy was evaluated by cytotoxicity tests. The results show that the mechanical milling and sintering temperatures have significantly effects on the density and mechanical properties of the alloys. The relative density of the alloy fabricated by the atomized powders at 1500 °C is only 83 ± 1.8%, while the relative density of the alloy fabricated by the ball-milled powders can rapidly reach at 96.4 ± 1.3% at 1500 °C. When the temperature was increased to 1550 °C, the alloy fabricated by ball-milled powders achieve full density (relative density is 98.1 ± 1.2%). The PM-fabricated Ti-28Nb-35.4Zr alloy by ball-milled powders at 1550 °C can achieve a wide range of mechanical properties, with a compressive yield strength of 1058 ± 35.1 MPa, elastic modulus of 50.8 ± 3.9 GPa, and hardness of 65.8 ± 1.5 HRA. The in vitro cytotoxicity test suggests that the PM-fabricated Ti-28Nb-35.4Zr alloy by ball-milled powders at 1550 °C has no adverse effects on MC3T3-E1 cells with cytotoxicity ranking of 0 grade, which is nearly close to ELI Ti-6Al-4V or CP Ti. These properties and the net-shape manufacturability makes PM-fabricated Ti-28Nb-35.4Zr alloy a low-cost, highly-biocompatible, Ti-based biomedical alloy.

Biocompatible Materials Based on Self-Assembling Peptides on Ti25Nb10Zr Alloy: Molecular Structure and Organization Investigated by Synchrotron Radiation Induced Techniques

In this work, we applied advanced Synchrotron Radiation (SR) induced techniques to the study of the chemisorption of the Self Assembling Peptide EAbuK16, i.e., H-Abu-Glu-Abu-Glu-Abu-Lys-Abu-Lys-Abu-Glu-Abu-Glu-Abu-Lys-Abu-Lys-NH₂ that is able to spontaneously aggregate in anti-parallel β-sheet conformation, onto annealed Ti25Nb10Zr alloy surfaces. This synthetic amphiphilic oligopeptide is a good candidate to mimic extracellular matrix for bone prosthesis, since its β-sheets stack onto each other in a multilayer oriented nanostructure with internal pores of 5–200 nm size. To prepare the biomimetic material, Ti25Nb10Zr discs were treated with aqueous solutions of EAbuK16 at different pH values. Here we present the results achieved by performing SR-induced X-ray Photoelectron Spectroscopy (SR-XPS), angle-dependent Near Edge X-ray Absorption Fine Structure (NEXAFS) spectroscopy, FESEM and AFM imaging on Ti25Nb10Zr discs after incubation with self-assembling peptide solution at five different pH values, selected deliberately to investigate the best conditions for peptide immobilization.

Development of hafnium metal and titanium-hafnium alloys having apatite-forming ability by chemical surface modification

Hafnium (Hf) has attracted considerable attention as a component of biomedical titanium (Ti) alloys with low Young's moduli and/or shape-memory functionalities, because its cytotoxicity is as low as that of Ti. The drawback of metals is that their bone-bonding ability is generally low. It is known that apatite formation in the body is a prerequisite for bone-bonding. Although several chemical treatments have been proposed for preparing Ti for bone-bonding, there have been no similar investigations for Hf. In the present study, NaOH- and heat-treatments were applied to pure Hf and Ti-Hf alloys and their bone-bonding ability was assessed in vitro with the use of simulated body fluid (SBF). After NaOH- and heat-treatments, anatase formed on alloys with low Hf content (20-40% (atom%) Hf); mixtures of sodium titanate and hafnium titanate formed on alloys with similar Ti and Hf content (60% Hf); and hafnium oxide formed on alloys with high Hf content (80% Hf and pure Hf). Precipitates of apatite were observed on all the metals in SBF, except for the alloy with 60% Hf. We speculated that the hafnium titanate formed on this alloy had a low apatite-forming ability owing to its high negative surface charge, which inhibited P adsorption. The apatite-forming abilities of the Ti-Hf alloys strongly depended on their Hf content. The present results indicate that Hf-based materials have good potential for bone-bonding. © 2018 Wiley Periodicals, Inc. J Biomed Mater Res Part B: Appl Biomater, 106B: 2519-2523, 2018.

Biocompatibility and Degradation of a Low Elastic Modulus Ti-35Nb-3Zr Alloy: Nanosurface Engineering for Enhanced Degradation Resistance

In this study, the biocompatibility and degradation behavior of a low elastic modulus Ti-35Nb-3Zr alloy were investigated and compared with that of the conventional orthopedic and dental implant materials, i.e., commercially pure titanium (Cp-Ti) and Ti-6Al-4V alloy. The biocompatibility test results suggested that cells proliferate equally well on Ti-35Nb-3Zr and Cp-Ti. The degradation rates of Cp-Ti and Ti-6Al-4V were ∼68% (p < 0.05) and ∼84% (p < 0.05) lower as compared to Ti-35Nb-3Zr, respectively. Interestingly, the passive current density (i_{pass (1000mv)}) of the Ti-35Nb-3Zr alloy was ∼29% lower than that of Cp-Ti, which suggests that the alloying elements in the Ti-35Nb-3Zr alloy have contributed to its passivation behavior. Nanosurface engineering of the Ti-35Nb-3Zr alloy, i.e., a two-step electrochemical process involving anodization (producing nanoporous layer) and calcium phosphate (CaP) deposition, decreased the degradation rate of the alloy by ∼83% (p < 0.05), and notably, it was similar to the conventional Ti-6Al-4V alloy. Hence, it can be suggested that the nanosurface-engineered low elastic modulus Ti-35Nb-3Zr alloy is a promising material for orthopedic and dental implant applications.

Novel Ti-Ta-Hf-Zr alloys with promising mechanical properties for prospective stent applications

Titanium alloys are receiving increasing research interest for the development of metallic stent materials due to their excellent biocompatibility, corrosion resistance, non-magnetism and radiopacity. In this study, a new series of Ti-Ta-Hf-Zr (TTHZ) alloys including Ti-37Ta-26Hf-13Zr, Ti-40Ta-22Hf-11.7Zr and Ti-45Ta-18.4Hf-10Zr (wt.%) were designed using the d-electron theory combined with electron to atom ratio (e/a) and molybdenum equivalence (Moeq) approaches. The microstructure of the TTHZ alloys were investigated using optical microscopy, XRD, SEM and TEM and the mechanical properties were tested using a Vickers micro-indenter, compression and tensile testing machines. The cytocompatibility of the alloys was assessed using osteoblast-like cells in vitro. The as-cast TTHZ alloys consisted of primarily β and ω nanoparticles and their tensile strength, yield strength, Young's modulus and elastic admissible strain were measured as being between 1000.7-1172.8 MPa, 1000.7-1132.2 MPa, 71.7-79.1 GPa and 1.32-1.58%, respectively. The compressive yield strength of the as-cast alloys ranged from 1137.0 to 1158.0 MPa. The TTHZ alloys exhibited excellent cytocompatibility as indicated by their high cell viability ratios, which were close to that of CP-Ti. The TTHZ alloys can be anticipated to be promising metallic stent materials by virtue of the unique combination of extraordinarily high elastic admissible strain, high mechanical strength and excellent biocompatibility.

Electrochemical comparison and biological performance of a new CoCrNbMoZr alloy with commercial CoCrMo alloy

A new CoCrNbMoZr alloy, with Nb and Zr content is characterized from the point of view of surface features, corrosion resistance and biological performance in order to be proposed as dental restorative material. Its properties are discussed in comparison with commercial Heraenium CE alloy based on Co, Cr and Mo as well. The microstructure of both alloys was revealed by scanning electron microscopy (SEM). The composition and thickness of the alloy native passive films were identified by X-ray photoelectron spectroscopy (XPS). The surface characteristics were analyzed by atomic force microscopy (AFM) and contact angle techniques. The quantity of ions released from alloys in artificial saliva was evaluated with inductively coupled plasma-mass spectroscopy (ICP-MS) measurements. The electrochemical stability was studied in artificial Carter-Brugirard saliva, performing open circuit potentials, polarization resistances and corrosion currents and rates. The biological performance of the new alloy was tested in vitro in terms of human adipose stem cells (hASCs) morphology, viability and proliferation status. The new alloy is very resistant to the attack of the aggressive ions from the artificial saliva. The surface properties, the roughness and wettabiliy sustain the cell behavior. The comparison of the new alloy behavior with that of existing commercial CoCrMo alloy showed the superior properties of the new metallic biomaterial.

Mechanical and physicochemical characterization along with biological interactions of a new Ti25Nb21Hf alloy for bone tissue engineering

Nowadays, one of the main challenges in metal implants for bone substitution is the achievement of an elastic modulus close to that of human cortical bone as well as to provide an adequate interaction with the surrounding tissue avoiding in vivo foreign body reaction. From this perspective, a new Ti-based alloy has been developed with Nb and Hf as alloying elements which are known as non-toxic and with good corrosion properties. The microstructure, mechanical behaviour and the physicochemical properties of this novel titanium alloy have been studied. Relationship of surface chemistry and surface electric charge with protein adsorption and cell adhesion has been evaluated due to its role for understanding the mechanism of biological interactions with tissues. The Ti25Nb21Hf alloy presented a lower elastic modulus than commercial alloys with a superior ultimate strength and yield strength than CP-Ti and very close to Ti6Al4V. It also exhibited good corrosion resistance. Furthermore, the results revealed that it had no cytotoxic effect on rat mesenchymal stem cells and allowed protein adsorption and cell adhesion. The experimental results make this alloy a promising material for bone substitution or for biomedical devices.

Microstructure, mechanical properties, castability and in vitro biocompatibility of Ti-Bi alloys developed for dental applications

In this study, the microstructure, mechanical properties, castability, electrochemical behaviors, cytotoxicity and hemocompatibility of Ti-Bi alloys with pure Ti as control were systematically investigated to assess their potential applications in the dental field. The experimental results showed that, except for the Ti-20Bi alloy, the microstructure of all other Ti-Bi alloys exhibit single α-Ti phase, while Ti-20Bi alloy is consisted of mainly α-Ti phase and a small amount of BiTi2 and BiTi3 phases. The tensile strength, hardness and wear resistance of Ti-Bi alloys were demonstrated to be improved monotonically with the increase of Bi content. The castability test showed that Ti-2Bi alloy increased the castability of pure Ti by 11.7%. The studied Ti-Bi alloys showed better corrosion resistance than pure Ti in both AS (artificial saliva) and ASFL (AS containing 0.2% NaF and 0.3% lactic acid) solutions. The concentrations of both Ti ion and Bi ion released from Ti-Bi alloys are extremely low in AS, ASF (AS containing 0.2% NaF) and ASL (AS containing 0.3% lactic acid) solutions. However, in ASFL solution, a large number of Ti and Bi ions are released. In addition, Ti-Bi alloys produced no significant deleterious effect to L929 cells and MG63 cells, similar to pure Ti, indicating a good in vitro biocompatibility. Besides, both L929 and MG63 cells perform excellent cell adhesion ability on Ti-Bi alloys. The hemolysis test exhibited that Ti-Bi alloys have an ultra-low hemolysis percentage below 1% and are considered nonhemolytic. To sum up, the Ti-2Bi alloy exhibits the optimal comprehensive performance and has great potential for dental applications.

Composition and Modifications of Dental Implant Surfaces

Since Brånemark discovered the favorable effects of titanium in bone healing in 1965, titanium has emerged as the gold standard bulk material for present-time dental implantology. In the course of years researchers aimed for improvement of the implants performance in bone even at compromised implant sites and multiple factors were investigated influencing osseointegration. This review summarizes and clarifies the four factors that are currently recognized being relevant to influence the tissue-implant contact ratio: bulk materials and coatings, topography, surface energy, and biofunctionalization. The macrodesigns of bulk materials (e.g., titanium, zirconium, stainless steel, tantalum, and magnesium) provide the mechanical stability and their influence on bone cells can be additionally improved by surface treatment with various materials (calcium phosphates, strontium, bioglasses, diamond-like carbon, and diamond). Surface topography can be modified via different techniques to increase the bone-implant contact, for example, plasma-spraying, grit-blasting, acid-etching, and microarc oxidation. Surface energy (e.g., wettability and polarity) showed a strong effect on cell behavior and cell adhesion. Functionalization with bioactive molecules (via physisorption, covalent binding, or carrier systems) targets enhanced osseointegration. Despite the satisfying clinical results of presently used dental implant materials, further research on innovative implant surfaces is inevitable to pursuit perfection in soft and hard tissue performance.

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.

Novel Ti-Zr-Hf-Fe Nanostructured Alloy for Biomedical Applications

The synthesis and characterization of Ti40Zr20Hf20Fe20 (atom %) alloy, in the form of rods (f = 2 mm), prepared by arc-melting, and subsequent Cu mold suction casting, is presented. The microstructure, mechanical and corrosion properties, as well as in vitro biocompatibility of this alloy, are investigated. This material consists of a mixture of several nanocrystalline phases. It exhibits excellent mechanical behavior, dominated by high strength and relatively low Young's modulus, and also good corrosion resistance, as evidenced by the passive behavior in a wide potential window and the low corrosion current densities values. In terms of biocompatibility, this alloy is not cytotoxic and preosteoblast cells can easily adhere onto its surface and differentiate into osteoblasts.

Electrospun eri silk fibroin scaffold coated with hydroxyapatite for bone tissue engineering applications

Natural biomaterials such as collagen, silk fibroin, and chitosan, and synthetic biopolymers such as polylactic acid, polycaprolactone, polyglycolic acid, and their copolymers are being used as scaffold for tissue engineering applications. In the present work, a fibrous mat was electrospun from eri silk fibroin (ESF). A composite of hydroxyapatite (Hap) and the ESF scaffold was prepared by soaking the ESF scaffold in a solution of calcium chloride and then in sodium diammonium phosphate. The average tensile stress of the pure ESF and hydroxyapatite-coated ESF scaffold (ESF-Hap) was found to be 1.84 and 0.378 MPa, respectively. Pure ESF and ESF-Hap scaffolds were evaluated for their characteristics by a themogravimetric analyzer and Fourier transform infrared spectroscope. The crystallinity and thermal stability of the ESF-Hap scaffold were found to be more than that of uncoated eri silk nanofiber scaffold. The water uptake of the pure ESF and ESF-Hap scaffolds was found to be 69% and 340%, respectively, in distilled water as well as phosphate buffer saline. The hemolysis percentage of both scaffolds was less than 5%, which indicate their good blood compatibility. The cytocompatibility studied by 3-(4,5-dimethyl) thiazol-2-yl-2,5-dimethyl tetrazolium bromide assay showed that the scaffold is biocompatible. To assess cell attachment and growth on the scaffold, human mesenchymal stem cells were cultured on the scaffolds. The results from scanning electron microscopy and fluorescent microscopy showed a notable cellular growth and favorable morphological features. Hence, the ESF-Hap scaffold is better suited for cell growth than the pure ESF scaffold.

Immortalized gingival fibroblasts as a cytotoxicity test model for dental materials

In vitro cytotoxicity test is an initial step to identify the harmful effects of new dental materials. Aim of this study was to develop a stable human cell line derived from normal gingival fibroblasts (hNOF) and to assess its feasibility in in vitro cytotoxicity testing. Immortalized human gingival fibroblasts (hTERT-hNOF) were successfully established with human telomerase reverse transcriptase gene transfection, preserving its phenotypical characteristics, replicative potential and biological properties. Utilizing standard cytotoxicity test modeling and dental materials, hTERT-hNOF were evaluated for their feasibility in cytotoxicity testing, compared with hNOF and L929 cells. Similar pattern of cytotoxic response was observed among hNOF, hTERT-hNOF and L929 cells. Cytotoxicity response of hTERT-hNOF was significantly similar to hNOF, moreover hTERT-hNOF and hNOF were found to be more sensitive towards the tested dental materials compared to L929 cells. This study suggested that hTERT-hNOF is an effective cytotoxic test model for dental materials.