New Developments of Ti-Based Alloys for Biomedical Applications

On the Ion Implantation Synthesis of Ag-Embedded Over Sr-Substituted Hydroxyapatite on a Nano-Topography Patterned Ti for Application in Acetabular Fracture Sites

Introduction

There is an ongoing need for improved healing response and expedited osseointegration on the Ti implants in acetabular fracture sites. To achieve adequate bonding and mechanical stability between the implant surface and the acetabular fracture, a new coating technology must be developed to promote bone integration and prevent bacterial growth.

Methods

A cylindrical Ti substrate mounted on a rotating specimen holder was used to implant Ca2+, P2+, and Sr2+ ions at energies of 100 KeV, 75 KeV and 180 KeV, respectively, using a low-energy accelerator to synthesize strontium-substituted hydroxyapatite at varying conditions. Ag2+ ions of energy 100 KeV were subsequently implanted on the as-formed surface at the near-surface region to provide anti-bacterial properties to the as-formed specimen.

Results

The properties of the as-formed ion-implanted specimen were compared with the SrHA-Ag synthesized specimens by cathodic deposition and low-temperature high-speed collision technique. The adhesion strength of the ion-implanted specimen was 43 ± 2.3 MPa, which is well above the ASTM standard for Ca-P coating on Ti. Live/dead cell analysis showed higher osteoblast activity on the ion-implanted specimen than the other two. Ag in the SrHA implanted Ti by ion implantation process showed superior antibacterial activity.

Discussion

In the ion implantation technique, nano-topography patterned surfaces are not concealed after implantation, and their efficacy in interacting with the osteoblasts is retained. Although all three studies examined the antibacterial effects of Ag2+ ions and the ability to promote bone tissue formation by MC3T3-E1 cells on SrHA-Ag/Ti surfaces, ion implantation techniques demonstrated superior ability. The synthesized specimen can be used as an effective implant in acetabular fracture sites based on their mechanical and biological properties.

The Effect of Solution Treatment Duration on the Microstructural and Mechanical Properties of a Cold-Deformed-by-Rolling Ti-Nb-Zr-Ta-Sn-Fe Alloy

The study presented in this paper is focused on the effect of varying the solution treatment duration on both the microstructural and mechanical properties of a cold-deformed by rolling Ti-30Nb-12Zr-5Ta-2Sn-1.25Fe (wt.%) alloy, referred to as TNZTSF. Cold-crucible induction using the levitation synthesis technique, conducted under an argon-controlled atmosphere, was employed to fabricate the TNZTSF alloy. After synthesis, the alloy underwent cold deformation by rolling, reaching a total deformation degree (total applied thickness reduction) of 60%. Subsequently, a solution treatment was conducted at 850 °C, with varying treatment durations ranging from 2 to 30 min in 2 min increments. X-ray diffraction (XRD) and scanning electron microscopy (SEM) techniques were utilized for the structural analysis, while the mechanical properties were assessed using both tensile and hardness testing. The findings indicate that (i) in both the cold-deformed-by-rolling and solution-treated states, the TNZTSF alloy exhibits a microstructure consisting of a single β-Ti phase; (ii) in the solution-treated state, the microstructure reveals a rise in the average grain size and a decline in the internal average microstrain as the duration of the solution treatment increases; and (iii) owing to the β-phase stability, a favorable mix of elevated strength and considerable ductility properties can be achieved.

Sliding and Fretting Wear Behavior of Biomedical Ultrafine-Grained TiNbZrTaFe/Si Alloys in Simulated Physiological Solution

This work investigated the wear behavior of ultrafine-grained Ti65Nb23.33Zr5Ta1.67Fe5 (at.%, TNZTF) and Ti65Nb23.33Zr5Ta1.67Si5 (at.%, TNZTS) alloys fabricated by high-energy ball milling and spark plasma sintering. Wear tests were conducted in a simulated physiological solution under both reciprocating sliding and fretting wear conditions with different loads, frequencies, and stroke lengths. The microstructures, mechanical properties, and anti-wear properties of the investigated alloys were characterized. The results showed that the TNZTF and TNZTS alloys had much less wear volume than the commonly used Ti-6Al-4V (TC4) alloy and commercially pure titanium (CP-Ti). The TNZTF and TNZTS alloys exhibited much more smooth wear surfaces and shallower wear scars compared with TC4 and CP-Ti. The investigated alloys exhibited different wear mechanisms under the reciprocating sliding wear conditions, while they were similar under the fretting wear conditions. Compared with TC4 and CP-Ti, the fabricated TNZTF and TNZTS alloys showed a substantially higher wear resistance, owing to their ultrafine-grained microstructure and superior hardness. Additionally, the addition of Nb and Zr further enhanced the wear resistance by forming a protective Nb2O5 and ZrO2 oxide film. This work provides guidance for designing new biomedical titanium alloys with excellent wear resistance.

Unveiling the spatial differentiation drivers of major soil element behavior along traffic network accessibility

Advancements in transportation networks have induced a spatial-temporal convergence effect, accelerating socio-economic elements flow and dismantling the conventional "core-periphery" urbanization gradient. Accessibility of transportation networks emerges as a reliable indicator of urbanization. There has been a growing global and Chinese focus on the various forms of metal pollution in urban soil. This study aims to investigate the driving forces and effects of urbanization factors (Gross Domestic Product (GDP), value added of secondary industries (VA), night light (NL), population density (PD), and road density (Distance)), soil property factors (pH, electrical conductivity (EC), and total organic carbon (TOC)), and topographic factors (elevation (DEM), aspect, and slope) on toxic heavy metal elements (Cd, As, and Hg) and trace elements (Mn, Ti, V) in surface soil (0-20 cm) across varying accessibility levels in the Beijing-Tianjin-Hebei urban agglomeration. Results reveal significant influence of accessibility on Cd and Hg levels (p < 0.05), with higher accessibility areas displaying elevated element concentrations. According to the evaluation results of the single-factor pollution index, Cd and V have the highest pollution exceedance rates (93.18% and 75.76%, respectively). Moran's Index results highlight typical spatial clustering of elements, with hotspots in areas of high accessibility. Urbanization has led to distinct spatial agglomeration patterns in element concentrations and environmental factors. Geographic detector analysis reveal that in low accessibility areas, metal element pollution and distribution are influenced by a combination of complex factors, including soil properties (pH), terrain conditions (DEM), and the urbanization process (VA). In high accessibility areas, toxic heavy metal elements are primarily driven by urbanization factors, largely influenced by transportation activities, industrial development, and population density, while elements Mn, Ti, and V are still influenced by both natural processes and urbanization activities. These findings suggest that urbanization intensifies the impact on potential toxic elements in soil, and that trace elements are increasingly affected by urbanization, warranting further attention.

Study on Osseointegration Capability of β-Type Ti-Nb-Zr-Ta-Si Alloy for Orthopedic Implants

Osseointegration is the basic condition for orthopedic implants to maintain long-term stability. In order to achieve osseointegration, a low elastic modulus is the most important performance indicator. It is difficult for traditional titanium alloys to meet this requirement. A novel β-titanium alloy (Ti-35Nb-7Zr-5Ta)98Si2 was designed, which had excellent strength (a yield strength of 1296 MPa and a breaking strength 3263 MPa), an extremely low elastic modulus (37 GPa), and did not contain toxic elements. In previous in vitro studies, we confirmed the good biocompatibility of this alloy and similar bioactivity to Ti-6Al-4V, but no in vivo study was performed. In this study, Ti-6Al-4V and (Ti-35Nb-7Zr-5Ta)98Si2 were implanted into rabbit femurs. Imaging evaluation and histological morphology were performed, and the bonding strength and bone contact ratio of the two alloys were measured and compared. The results showed that both alloys remained in their original positions 3 months after implantation, and neither imaging nor histological observations found inflammatory reactions in the surrounding bone. The bone-implant contact ratio and bonding strength of (Ti-35Nb-7Zr-5Ta)98Si2 were significantly higher than those of Ti-6Al-4V. The results confirmed that (Ti-35Nb-7Zr-5Ta)98Si2 has a better osseointegration ability than Ti-6Al-4V and is a promising material for orthopedic implants.

Investigation of the Chemical Composition, Microstructure, Density, Microhardness, and Elastic Modulus of the New β Ti-50Nb-xMo Alloys for Biomedical Applications

β-type titanium alloys with a body-centered cubic structure are highly useful in orthopedics due to their low elastic modulus, lower than other commonly used alloys such as stainless steel and Co-Cr alloys. The formation of the β phase in titanium alloys is achieved through β-stabilizing elements such as Nb, Mo, and Ta. To produce new β alloys with a low modulus of elasticity, this work aimed to produce our alloy system for biomedical applications (Ti-50Nb-Mo). The alloys were produced by arc-melting and have the following compositions Ti-50Nb-xMo (x = 0, 3, 5, 7, and 12 wt% Mo). The alloys were characterized by density, X-ray diffraction, scanning electron microscopy, microhardness, and elastic modulus. It is worth highlighting that this new set of alloys of the Ti-50Nb-Mo system produced in this study is unprecedented; due to this, there needs to be a report in the literature on the production and structural characterization, hardness, and elastic modulus analyses. The microstructure of the alloys has an exclusively β phase (with bcc crystalline structure). The results show that adding molybdenum considerably increased the microhardness and decreased the elastic modulus, with values around 80 GPa, below the metallic materials used commercially for this type of application. From the produced alloys, Ti-50Nb-12Mo is highlighted due to its lower elastic modulus.

The role of stiffness-matching in avoiding stress shielding-induced bone loss and stress concentration-induced skeletal reconstruction device failure

It is well documented that overly stiff skeletal replacement and fixation devices may fail and require revision surgery. Recent attempts to better support healing and sustain healed bone have looked at stiffness-matching of these devices to the desired role of limiting the stress on fractured or engrafted bone to compressive loads and, after the reconstructed bone has healed, to ensure that reconstructive medical devices (implants) interrupt the normal loading pattern as little as possible. The mechanical performance of these devices can be optimized by adjusting their location, integration/fastening, material(s), geometry (external and internal), and surface properties. This review highlights recent research that focuses on the optimal design of skeletal reconstruction devices to perform during and after healing as the mechanical regime changes. Previous studies have considered auxetic materials, homogeneous or gradient (i.e., adaptive) porosity, surface modification to enhance device/bone integration, and choosing the device's attachment location to ensure good osseointegration and resilient load transduction. By combining some or all of these factors, device designers work hard to avoid problems brought about by unsustainable stress shielding or stress concentrations as a means of creating sustainable stress-strain relationships that best repair and sustain a surgically reconstructed skeletal site. STATEMENT OF SIGNIFICANCE: Although standard-of-care skeletal reconstruction devices will usually allow normal healing and improved comfort for the patient during normal activities, there may be significant disadvantages during long-term use. Stress shielding and stress concentration are amongst the most common causes of failure of a metallic device. This review highlights recent developments in devices for skeletal reconstruction that match the stiffness, while not interrupting the normal loading pattern of a healthy bone, and help to combat stress shielding and stress concentration. This review summarises various approaches to achieve stiffness-matching: application of materials with modulus close to that of the bone; adaptation of geometry with pre-defined mechanical properties; and/or surface modification that ensures good integration and proper load transfer to the bone.

Tribocorrosion and Surface Protection Technology of Titanium Alloys: A Review

Titanium alloy has the advantages of high specific strength, good corrosion resistance, and biocompatibility and is widely used in marine equipment, biomedicine, aerospace, and other fields. However, the application of titanium alloy in special working conditions shows some shortcomings, such as low hardness and poor wear resistance, which seriously affect the long life and safe and reliable service of the structural parts. Tribocorrosion has been one of the research hotspots in the field of tribology in recent years, and it is one of the essential factors affecting the application of passivated metal in corrosive environments. In this work, the characteristics of the marine and human environments and their critical tribological problems are analyzed, and the research connotation of tribocorrosion of titanium alloy is expounded. The research status of surface protection technology for titanium alloy in marine and biological environments is reviewed, and the development direction and trends in surface engineering of titanium alloy are prospected.

Influence of Oil Viscosity on the Tribological Behavior of a Laser-Textured Ti6Al4V Alloy

Laser texturing with a dimple pattern was applied to modify a Ti6Al4V alloy at the micro level, aiming to improve its friction and wear resistance in combination with oil lubrication to optimize the performance in demanding industrial environments. The tribological analysis was performed on four different dimple-textured surfaces with varying dimple size and dimple-to-dimple distance and under lubrication with three different oils, i.e., T9, VG46, and VG100, to reflect the oil viscosity's influence on the friction/wear of the laser-textured Ti6Al4V alloy. The results show that the surfaces with the highest texture density showed the most significant COF reduction of around 10% in a low-viscosity oil (T9). However, in high-viscosity oils (VG46 and VG100), the influence of the laser texturing on the COF was less pronounced. A wear analysis revealed that the laser texturing intensified the abrasive wear, especially on surfaces with a higher texture density. For low-texturing-density surfaces, less wear was observed for low- and medium-viscosity oils (T9 and VG46). For medium-to-high-texturing densities, the high-viscosity oil (VG100) provided the best contact conditions and wear results. Overall, reduced wear, even below the non-texturing case, was observed for sample 50-200 in VG100 lubrication, indicating the combined effect of oil reservoirs and increased oil-film thickness within the dimples due to the high viscosity.

Laser textured Ti-6Al-7Nb alloy for biomedical applications: An investigation of texturing parameters on surface properties

Surface texturing with a laser beam is an effective method for engraving on the surface of biomaterials. The four laser texturing parameters (scan speed, frequency, fill spacing, and pulse width) having five different values were associated with five different scanning strategies (scan direction), and a total of 25 texturing conditions were tested on the Ti-6Al-7Nb alloy surface. The surface roughness and wettability of the textures created with a 20 W nanosecond fiber laser with a wavelength of 1064 nm on the surface of Ti-6Al-7Nb biocompatible alloy were investigated. Laser texturing parameters were analyzed according to the lowest surface roughness and a hydrophilic surface by creating L25 orthogonal arrays. The surface roughness values ranged between 2 and 26 µm. The lowest surface roughness with a value of 2.21 µm was achieved when the texture was processed with a frequency of 150 kHz, a fill spacing of 0.02 mm, a scan speed of 800 mm/s, a pulse width of 250 ns, and a cross-hatch strategy of 0°/90°. Considering the wettability test results, it was revealed that most of the textured surfaces have super hydrophilic and hydrophilic characteristics except the surface with a contact angle of 92.93°. The relevant surface was textured with 75 kHz frequency, 1000 mm/s scan speed, 0.05 mm fill spacing, 200 ns pulse width, and 45°/-45° cross-hatch strategy.

Biocompatible Ti3Au-Ag/Cu thin film coatings with enhanced mechanical and antimicrobial functionality

BACKGROUND

Biofilm formation on medical device surfaces is a persistent problem that shelters bacteria and encourages infections and implant rejection. One promising approach to tackle this problem is to coat the medical device with an antimicrobial material. In this work, for the first time, we impart antimicrobial functionality to Ti3Au intermetallic alloy thin film coatings, while maintaining their superior mechanical hardness and biocompatibility.

METHODS

A mosaic Ti sputtering target is developed to dope controlled amounts of antimicrobial elements of Ag and Cu into a Ti3Au coating matrix by precise control of individual target power levels. The resulting Ti3Au-Ag/Cu thin film coatings are then systematically characterised for their structural, chemical, morphological, mechanical, corrosion, biocompatibility-cytotoxicity and antimicrobial properties.

RESULTS

X-ray diffraction patterns reveal the formation of a super hard β-Ti3Au phase, but the thin films undergo a transition in crystal orientation from (200) to (211) with increasing Ag concentration, whereas introduction of Cu brings no observable changes in crystal orientation. Scanning and transmission electron microscopy analysis show the polyhedral shape of the Ti3Au crystal but agglomeration of Ag particles between crystal grains begins at 1.2 at% Ag and develops into large granules with increasing Ag concentration up to 4.1 at%. The smallest doping concentration of 0.2 at% Ag raises the hardness of the thin film to 14.7 GPa, a 360% improvement compared to the ∼4 GPa hardness of the standard Ti6Al4V base alloy. On the other hand, addition of Cu brings a 315-330% improvement in mechanical hardness of films throughout the entire concentration range of 0.5-7.1 at%. The thin films also show good electrochemical corrosion resistance and a > tenfold reduction in wear rate compared to Ti6Al4V alloy. All thin film samples exhibit very safe cytotoxic profiles towards L929 mouse fibroblast cells when analysed with Alamar blue assay, with ion leaching concentrations lower than 0.2 ppm for Ag and 0.08 ppm for Cu and conductivity tests reveal the positive effect of increased conductivity on myogenic differentiation. Antimicrobial tests show a drastic reduction in microbial survival over a short test period of < 20 min for Ti3Au films doped with Ag or Cu concentrations as low as 0.2-0.5 at%.

CONCLUSION

Therefore, according to these results, this work presents a new antimicrobial Ti3Au-Ag/Cu coating material with excellent mechanical performance with the potential to develop wear resistant medical implant devices with resistance to biofilm formation and bacterial infection.

Interaction between Mesenchymal Stem Cells and Immune Cells during Bone Injury Repair

Fractures are the most common large organ trauma in humans. The initial inflammatory response promotes bone healing during the initial post-fracture phase, but chronic and persistent inflammation due to infection or other factors does not contribute to the healing process. The precise mechanisms by which immune cells and their cytokines are regulated in bone healing remain unclear. The use of mesenchymal stem cells (MSCs) for cellular therapy of bone injuries is a novel clinical treatment approach. Bone progenitor MSCs not only differentiate into bone, but also interact with the immune system to promote the healing process. We review in vitro and in vivo studies on the role of the immune system and bone marrow MSCs in bone healing and their interactions. A deeper understanding of this paradigm may provide clues to potential therapeutic targets in the healing process, thereby improving the reliability and safety of clinical applications of MSCs to promote bone healing.

Laser powder bed fusion (LPBF) of commercially pure titanium and alloy development for the LPBF process

Laser powder bed fusion (LPBF) of titanium or titanium alloys allows fabrication of geometrically more complex and, possibly, individualized implants or osteosynthesis products and could thus improve the outcome of medical treatments considerably. However, insufficient LPBF process parameters can result in substantial porosity, decreasing mechanical properties and requiring post-treatment. Furthermore, texturized parts with anisotropic properties are usually obtained after LPBF processing, limiting their usage in medical applications. The present study addresses both: first, a design of experiments is used in order to establish a set of optimized process parameters and a process window for LPBF printing of small commercially pure (CP) titanium parts with minimized volume porosity. Afterward, the first results on the development of a biocompatible titanium alloy designed for LPBF processing of medical implants with improved solidification and more isotropic properties are presented on the basis of conventionally melted alloys. This development was performed on the basis of Ti-0.44O-0.5Fe-0.08C-0.4Si-0.1Au, a near-α alloy presented by the authors for medical applications and conventional manufacturing, with yttrium and boron additions as additional growth restriction solutes. In terms of LPBF processing of CP titanium grade 1 powder, a high relative density of approximately 99.9% was obtained in the as-printed state of the volume of a small cubical sample by using optimized laser power, scanning speed, and hatch distance in combination with a rotating scanning pattern. Moreover, tensile specimens processed with these volume settings and tested in the as-printed milled state exhibited a high average yield and ultimate tensile strength of approximately 663 and 747 N/mm2, respectively, combined with a high average ductility of approximately 24%. X-ray diffraction results suggest anisotropic mechanical properties, which are, however, less pronounced in terms of the tested specimens. Regarding alloy development, the results show that yttrium additions lead to a considerable microstructure refinement but have to be limited due to the occurrence of a large amount of precipitations and a supposed higher propensity for the formation of long columnar prior β-grains. However, phase/texture and microstructure analyses indicate that Ti-0.44O-0.5Fe-0.08C-0.4Si-0.1Au-0.1B-0.1Y is a promising candidate to achieve lower anisotropy during LPBF processing, but further investigations on LPBF printing and Y2O3 formation are necessary.

Photoinduced properties of anodized Ti alloys for biomaterial applications

The photocatalytic properties of anodic oxides on a newly developed TiNbSn and commonly used Ti6Al4V alloys as biomaterials were investigated. The alloys were anodized in an electrolyte of sodium tartrate acid with H2O2 at a high voltage and the mechanism of the photocatalytic and antiviral activities was studied. The anodized TiNbSn and Ti6Al4V exhibited highly crystallized rutile TiO2 and poorly crystallized anatase TiO2, respectively. X-ray photoelectron spectroscopy analysis revealed the presence of oxides of the alloying elements in addition to TiO2. The anodized TiNbSn exhibited higher activities than Ti6Al4V, and electron spin resonance spectra indicated that the number of hydroxyl radicals (⋅OH) generated from the anodized TiNbSn was higher than that from the anodized Ti6Al4V. The results can be explained by two possible mechanisms: the higher crystallinity of TiO2 on TiNbSn than that on the Ti6Al4V reduces the number of charge recombination sites and generates abundant ⋅OH; charge separation in the anodic oxide on TiNbSn due to the electronic band structure between TiO2 and the oxides of alloying elements enhances photo activities. The excellent photoinduced characteristics of the anodized TiNbSn are expected to contribute to the safe and reliable implant treatment.

Manufacture of titanium alloy materials with bioactive sandblasted surfaces and evaluation of osseointegration properties

Titanium alloys are some of the most important orthopedic implant materials currently available. However, their lack of bioactivity and osteoinductivity limits their osseointegration properties, resulting in suboptimal osseointegration between titanium alloy materials and bone interfaces. In this study, we used a novel sandblasting surface modification process to manufacture titanium alloy materials with bioactive sandblasted surfaces and systematically characterized their surface morphology and physicochemical properties. We also analyzed and evaluated the osseointegration between titanium alloy materials with bioactive sandblasted surfaces and bone interfaces by in vitro experiments with co-culture of osteoblasts and in vivo experiments with a rabbit model. In our in vitro experiments, the proliferation, differentiation, and mineralization of the osteoblasts on the surfaces of the materials with bioactive sandblasted surfaces were better than those in the control group. In addition, our in vivo experiments showed that the titanium alloy materials with bioactive sandblasted surfaces were able to promote the growth of trabecular bone on their surfaces compared to controls. These results indicate that the novel titanium alloy material with bioactive sandblasted surface has satisfactory bioactivity and osteoinductivity and exhibit good osseointegration properties, resulting in improved osseointegration between the material and bone interface. This work lays a foundation for subsequent clinical application research into titanium alloy materials with bioactive sandblasted surfaces.

Mechanical influence of tissue scaffolding design with different geometries using finite element study

The mechanical properties of tissue scaffolds are essential in providing stability for tissue repair and growth. Thus, the ability of scaffolds to withstand specific loads is crucial for scaffold design. Most research on scaffold pores focuses on grids with pore size and gradient structure, and many research models are based on scaffolding with vertically arranged holes. However, little attention is paid to the influence of the distribution of holes on the mechanical properties of the scaffold. To address this gap, this research investigates the effect of pore distribution on the mechanical properties of tissue scaffolds. The study involves four types of scaffold designs with regular and staggered pore arrangements and porosity ranging from 30% to 80%. Finite element analysis (FEA) was used to compare the mechanical properties of different scaffold designs, with von-Mises stress distribution maps generated for each scaffold. The results show that scaffolds with regular vertical holes exhibit a more uniform stress distribution and better mechanical performance than those with irregular holes. In contrast, the scaffold with a staggered arrangement of holes had a higher probability of stress concentration. The study emphasized the importance of balancing porosity and strength in scaffold design.

XPS Characterization of TiO2 Nanotubes Growth on the Surface of the Ti15Zr15Mo Alloy for Biomedical Applications

Ti15Zr15Mo (TMZ alloy) has been studied in recent years for biomedical applications, mainly due to phase beta formation. From the surface modification, it is possible to associate the volume and surface properties with a better biomedical response. This study aimed to evaluate the possibility of using anodization to obtain TiO₂ nanotubes due to the presence of valve-type metal (Zr) in their composition. X-ray photoelectron spectroscopy (XPS) was performed to determine the surface chemical composition in both after-processing conditions (passive layer) and after-processing plus anodization (TiO₂ nanotube growth). The anodization resulted in nanotubes with diameters and thicknesses of 126 ± 35 and 1294 ± 193 nm, respectively, and predominated anatase phase. Compared to the passive layer of titanium, which is less than ~10 nm, the oxide layer formed was continuous and thicker. High-resolution spectra revealed that the oxide layer of the element alloys contained different oxidation states. The major phase in all depths for the nanotube samples was TiO2. While the stable form of each oxide was found to predominate on the surface, the inner part of the oxide layer consisted of suboxides and metallic forms. This composition included different oxidation states of the substrate elements Ti, Zr, and Mo.

Corrosion Passivation in Simulated Body Fluid of Ti-Zr-Ta-xSn Alloys as Biomedical Materials

The powder metallurgy method was used to manufacture three Ti-based alloys: Ti-15%Zr-2%Ta-4%Sn (Ti-Zr-Ta-4Sn), Ti-15%Zr-2%Ta-6%Sn (Ti-Zr-Ta-6Sn), and Ti-15%Zr-2%Ta-8%Sn (Ti-Zr-Ta-8Sn). Electrochemical measurements and surface analyses were used to determine the effect of Sn concentration on the corrosion of these alloys after exposure to a simulated body fluid (SBF) solution for 1 h and 72 h. It was found that the passivation of the alloy surface significantly increased when the Sn content increased from 4% to 6% and then to 8%, which led to a significant reduction in corrosion. The impedance spectra derived from the Nyquist graphs also explained how the addition of Sn significantly improved the alloys' polarization resistances. According to the change in the chronoamperometric current at an applied anodic potential over time, the increase in Sn content within the alloy significantly reduced the currents over time, indicating that the uniform and pitting corrosion were greatly decreased. The formation of an oxide layer (TiO₂), which was demonstrated by the surface morphology of the alloys after exposure to SBF solution for 72 h and corrosion at 400 mV (Ag/AgCl) for 60 min, was supported by the profile analysis obtained by an X-ray spectroscopy analyzer. It was clear from all of the findings that the tested alloys have a remarkable improvement in resistance to corrosivity when the Sn content was increased to 8%.

Effects of 3d Transition Metal Substitutions on the Phase Stability and Mechanical Properties of Ti-5.5Al-11.8[Mo]eq Alloys

The phase stability, mechanical properties, and functional properties of Ti-5.5Al-11.8[Mo]_eq alloys are focused on in this study by substituting 3d transition metal elements (V, Cr, Co, and Ni) for Mo as β-stabilizers to achieve similar β phase stability and room temperature (RT) superelasticity. The ternary alloy systems with the equivalent chemical compositions of Ti-5.5Al-17.7V, Ti-5.5Al-9.5Cr, Ti-5.5Al-7.0Co, and Ti-5.5Al-9.5Ni (mass%) alloys were selected as the target materials based on the Mo equivalent formula, which has been applied for the Ti-5.5Al-11.8Mo alloy in the literature. The fundamental mechanical properties and functionalities of the selected alloys were examined. The β phase was stabilized at RT in all alloys except for the Ti-Al-V alloy. Among all alloys, the Ti-Al-Ni alloy exhibited superelasticity in the cyclic loading-unloading tensile tests at RT. As a result, similar to the Ti-5.5Al-11.8Mo mother alloy, by utilizing the Mo equivalent formula to substitute 3d transition metal elements for Mo, a RT superelasticity was successfully imposed.

Influence of Aluminum and Copper on Mechanical Properties of Biocompatible Ti-Mo Alloys: A Simulation-Based Investigation

The use of titanium and titanium-based alloys in the human body due to their resistance to corrosion, implant ology and dentistry has led to significant progress in promoting new technologies. Regarding their excellent mechanical, physical and biological performance, new titanium alloys with non-toxic elements and long-term performance in the human body are described today. The main compositions of Ti-based alloys and properties comparable to existing classical alloys (C.P. TI, Ti-6Al-4V, Co-Cr-Mo, etc.) are used for medical applications. The addition of non-toxic elements such as Mo, Cu, Si, Zr and Mn also provides benefits, such as reducing the modulus of elasticity, increasing corrosion resistance and improving biocompatibility. In the present study, when choosing Ti-9Mo alloy, aluminum and copper (Cu) elements were added to it. These two alloys were chosen because one element is considered a favorable element for the body (copper) and the other element is harmful to the body (aluminum). By adding the copper alloy element to the Ti-9Mo alloy, the elastic modulus decreases to a minimum value of 97 GPa, and the aluminum alloy element increases the elastic modulus up to 118 GPa. Due to their similar properties, Ti-Mo-Cu alloys are found to be a good optional alloy to use.

Platelet-derived extracellular vesicles formulated with hyaluronic acid gels for application at the bone-implant interface: An animal study

Background/Objective

Platelet derived extracellular vesicles (pEV) are promising therapeutical tools for bone healing applications. In fact, several in vitro studies have already demonstrated the efficacy of Extracellular Vesicles (EV) in promoting bone regeneration and repair in various orthopedic models. Therefore, to evaluate the translational potential in this field, an in vivo study was performed.

Methods

Here, we used hyaluronic acid (HA) gels formulated with pEVs, as a way to directly apply pEVs and retain them at the bone defect. In this study, pEVs were isolated from Platelet Lysate (PL) through size exclusion chromatography and used to formulate 2% HA gels. Then, the gels were locally applied on the tibia cortical bone defect of New Zeland White rabbits before the surgical implantation of coin-shaped titanium implants. After eight weeks, the bone healing process was analyzed through biomechanical, micro-CT, histological and biochemical analysis.

Results

Although no biomechanical differences were observed between pEV formulated gels and non-formulated gels, biochemical markers of the wound fluid at the interface presented a decrease in Lactate dehydrogenase (LDH) activity and alkaline phosphatase (ALP) activity for pEV HA treated implants. Moreover, histological analyses showed that none of the treatments induced an irritative effect and, a decrease in the fibrotic response surrounding the implant for pEV HA treated implants was described.

Conclusion

In conclusion, pEVs improve titanium implants biocompatibility at the bone-implant interface, decreasing the necrotic effects of the surgery and diminishing the fibrotic layer associated to the implant encapsulation that can lead to implant failure.

Microstructural Considerations of a Multi-Pass Rolled Ti-Nb-Ta-Zr Alloy

The microstructural characteristic evolution was investigated during thermomechanical processing of Ti-29Nb-9Ta-10Zr (wt %) alloy, which consisted of, in a first stage, in a Multi-Pass Rolling with increasing thickness reduction of 20%, 40%, 60%, 80%, and 90%; in step two, the multi-pass rolled sample with the highest thickness reduction (90%) was subjected to a series of three variants of static short recrystallization and then to a final similar aging. The objective was to evaluate the microstructural features evolution during thermomechanical processing (phase's nature, morphology, dimensions, and crystallographic characteristics) and to find the optimal heat treatment variant for refinement of the alloy granulation until ultrafine/nanometric level for a promising combination of mechanical properties. The microstructural features were investigated by X-ray diffraction and SEM techniques through which the presence of two phases was recorded: the β-Ti phase and the α″-Ti martensitic phase. The corresponding cell parameters, dimensions of the coherent crystallite and the micro-deformations at the crystalline network level for both recorded phases were determined. The majority β-Ti phase underwent a strong refinement during the Multi-Pass Rolling process until ultrafine/nano grain dimension (about 9.8 nm), with subsequent slow growing during recrystallization and aging treatments, hindered by the presence of sub-micron α″-Ti phase dispersed inside β-Ti grains. An analysis concerning the possible deformation mechanisms was performed.

The effect of strontium content on physicochemical and osteogenic property of Sr/Ag-containing TiO2 microporous coatings

Strontium (Sr) is the most common element introduced into TiO₂ coatings to strengthen the osteogenic property of titanium implants. However, the optimal Sr content and its effect on osteogenic and physicochemical properties of the coatings need to be clarified. In the current study, TiO₂ microporous coatings with different contents of Sr (9.64-21.25 wt %) and silver (Ag) (0.38-0.75 wt %) were prepared via micro-arc oxidation technique. Sr contents did not change physicochemical properties of the coatings, including surface microstructure, micropore size and distribution, phase composition, roughness and hydrophilicity. Meanwhile, higher Sr contents (18.23-21.25 wt %) improved cytocompatibility, proliferation and alkaline phosphatase (ALP) activity of preosteoblasts, even the coatings underwent 30 days' PBS immersion. Furthermore, higher Sr contents facilitated preosteoblast growth and spreading, which are essential for their proliferation and osteogenic differentiation. Therefore, it is promising to incorporate higher Sr content (18.23-21.25 wt %) within TiO₂ microporous coatings to improve their osteogenic capability.

Design of Ti-Mo-W Alloys and Its Correlation with Corrosion Resistance in Simulated Body Fluid (SBF)

Titanium and its based alloys are frequently selected for designing biomedical implants and it is thus necessary to study as detailed as possible their corrosion behavior in biological solutions, such as those in the human body environment. In this paper, with the use of molecular orbital calculation, we designed and developed alloys in the Ti-19Mo-xW system (x = 7, 8, 9, and 10 wt%) and investigated the influence of different contents of tungsten on the behavior of Ti-19Mo-xW alloy samples following corrosion in simulated body fluid (SBF). The values of Bo¯ (bond order) and Md¯ (the metal-orbital energy level) were calculated for each alloy and correlations were established between Bo¯ and the content of tungsten. It was found that with the increase in tungsten content, the value of Bo¯ increases. Regarding the values of the corrosion resistance in SBF that resulted from the investigated alloys, the Ti19Mo7W alloy is distinguished by the lowest value of the corrosion current density and the lowest corrosion rate.

Osteogenic and long-term antibacterial properties of Sr/Ag-containing TiO2 microporous coating in vitro and in vivo

Bacterial infection and poor osseointegration are two critical issues that need to be solved for long-term use of titanium implants. As such, Sr/Ag-containing TiO₂ microporous coatings were prepared on a Ti alloy surface in the current study via a single-step microarc oxidation technique. The coatings showed both good cytocompatibility in vitro and biosafety in vivo. Sr/Ag incorporation brought no significant change in the surface micromorphology and physicochemical properties, but endowed the coating with strong osteogenic activity and long-term antibacterial capability in vitro. Furthermore, the osteogenic and antibacterial capability of the coating was also confirmed in vivo. In a rat osseointegration model, new bone formation, implant-bone contact, removal torque and bone mineralization were all significantly increased in the M-Sr/Ag group when compared with those in group M, although they were slightly lower than those in group M-Sr. In a periimplantitis model, no rats suffered infection in the M-Sr/Ag group after 3 months of osseointegration and 5 weeks of bacterial inoculation period, when compared to 100% and 75% infection rates in M and M-Sr groups, respectively. In addition, active bone remodeling and many mesenchymal cells were observed in the M-Sr group, suggesting good bone regeneration potential in Sr-containing coatings in the case of controlled periimplantitis. Overall, the Sr/Ag-containing TiO₂ microporous coating is valuable for preventing periimplantitis and improving implant reosseointegration, and is therefore promising for long-term and high quality use of titanium implants.

DMP1 and IFITM5 Regulate Osteogenic Differentiation of MC3T3-E1 on PEO-Treated Ti-6Al-4V-Ca2+/Pi surface

Despite numerous studies on various surface modifications on titanium and its alloys, it remains unclear what kind of titanium-based surface modifications are capable of controlling cell activity. This study aimed to understand the mechanism at the cellular and molecular levels and investigate the in vitro response of osteoblastic MC3T3-E1 cultured on the Ti-6Al-4V surface modified by plasma electrolytic oxidation (PEO) treatment. A Ti-6Al-4V surface was prepared by PEO at 180, 280, and 380 V for 3 or 10 min in an electrolyte containing Ca²⁺/P_i ions. Our results showed that PEO-treated Ti-6Al-4V-Ca²⁺/P_i surfaces enhanced the cell attachment and differentiation of MC3T3-E1 compared to the untreated Ti-6Al-4V control but did not affect cytotoxicity as shown by cell proliferation and cell death. Interestingly, on the Ti-6Al-4V-Ca²⁺/P_i surface treated by PEO at 280 V for 3 or 10 min, MC3T3-E1 showed a higher initial adhesion and mineralization. In addition, the alkaline phosphatase (ALP) activity significantly increased in MC3T3-E1 on the PEO-treated Ti-6Al-4V-Ca²⁺/P_i (280 V for 3 or 10 min). In RNA-seq analysis, the expression of dentin matrix protein 1 (DMP1), sortilin 1 (Sort1), signal-induced proliferation-associated 1 like 2 (SIPA1L2), and interferon-induced transmembrane protein 5 (IFITM5) was induced during the osteogenic differentiation of MC3T3-E1 on the PEO-treated Ti-6Al-4V-Ca²⁺/P_i. DMP1 and IFITM5 silencing decreased the expression of bone differentiation-related mRNAs and proteins and ALP activity in MC3T3-E1. These results suggest that the PEO-treated Ti-6Al-4V-Ca²⁺/P_i surface induces osteoblast differentiation by regulating the expression of DMP1 and IFITM5. Therefore, surface microstructure modification through PEO coatings with Ca²⁺/P_i ions could be used as a valuable method to improve biocompatibility properties of titanium alloys.

Improving Biocompatibility for Next Generation of Metallic Implants

The increasing need for joint replacement surgeries, musculoskeletal repairs, and orthodontics worldwide prompts emerging technologies to evolve with healthcare's changing landscape. Metallic orthopaedic materials have a shared application history with the aerospace industry, making them only partly efficient in the biomedical domain. However, suitability of metallic materials in bone tissue replacements and regenerative therapies remains unchallenged due to their superior mechanical properties, eventhough they are not perfectly biocompatible. Therefore, exploring ways to improve biocompatibility is the most critical step toward designing the next generation of metallic biomaterials. This review discusses methods of improving biocompatibility of metals used in biomedical devices using surface modification, bulk modification, and incorporation of biologics. Our investigation spans multiple length scales, from bulk metals to the effect of microporosities, surface nanoarchitecture, and biomolecules such as DNA incorporation for enhanced biological response in metallic materials. We examine recent technologies such as 3D printing in alloy design and storing surface charge on nanoarchitecture surfaces, metal-on-metal, and ceramic-on-metal coatings to present a coherent and comprehensive understanding of the subject. Finally, we consider the advantages and challenges of metallic biomaterials and identify future directions.

Titanium Lattice Structures Produced via Additive Manufacturing for a Bone Scaffold: A Review

The progress in additive manufacturing has remarkably increased the application of lattice materials in the biomedical field for the fabrication of scaffolds used as bone substitutes. Ti6Al4V alloy is widely adopted for bone implant application as it combines both biological and mechanical properties. Recent breakthroughs in biomaterials and tissue engineering have allowed the regeneration of massive bone defects, which require external intervention to be bridged. However, the repair of such critical bone defects remains a challenge. The present review collected the most significant findings in the literature of the last ten years on Ti6Al4V porous scaffolds to provide a comprehensive summary of the mechanical and morphological requirements for the osteointegration process. Particular attention was given on the effects of pore size, surface roughness and the elastic modulus on bone scaffold performances. The application of the Gibson–Ashby model allowed for a comparison of the mechanical performance of the lattice materials with that of human bone. This allows for an evaluation of the suitability of different lattice materials for biomedical applications.

Midterm results of titanium conical Wagner stem with challenging femoral anatomy: Survivorship and unique bone remodeling

BACKGROUND

Complex anatomy of the proximal femur makes total hip arthroplasty (THA) more challenging. Short, straight, fluted and conical titanium stem like the Wagner Cone can be helpful to address small femoral canal, increased femoral neck version, important leg length discrepancy or proximal femoral deformity. The outcome in these patients is less assured and associated with high rate of complications. Therefore, we did a retrospective study aiming to answer: 1) can the Wagner Cone stem provide acceptable mid- to long-term implant survivorship; 2) help minimizing perioperative adverse events; 3) produce favorable clinical outcome measured by WOMAC score; and 4) be associated with a favorable radiographic femoral bone remodeling at the last follow-up?

HYPOTHESIS

Wagner Cone stem is an advantageous solution for the distorted proximal femur in complex THA.

PATIENTS AND METHOD

Our cohort was derived from the patient registries where medical records of 88 patients (103 hips) who underwent primary THA using the Wagner prosthesis were retrospectively reviewed. Then, data was analyzed for patients' demographics and surgical data, and comparing preoperative, immediate postoperative and last follow-up data. Eleven patients (12 hips) were excluded (7 hips followed up less than 2 years or lost to follow-up, 3 hips that had the Wagner stem for revision and 2 Wagner stems inserted for periprosthetic fracture). This left 77 patients (91 hips) with Wagner cone stems implanted for more than 2 years between March 2003 and February 2017 by 7 surgeons in 3 academic hospitals. Implant revision, reoperations, WOMAC score and radiographic analyses were recorded at last follow-up.

RESULTS

After a mean follow-up of 7.8 (range, 2.0-16.2) years, Wagner stem survivorship was 98.9% (95% CI: 94 to 100%) with one (1.1%) stem revision for failure of osteointegration. Five (5.5%) acetabular revisions, one for aseptic loosening, 2 for adverse reaction to metal debris and 2 for infection. One (1.1%) sciatic neuropathy and 4 (4.4%) intraoperative fractures were encountered. The mean WOMAC score was 90.5±11.4 (59-100). Radiographic analysis showed clear signs of stem osseointegration and hypertrophic bone remodeling in 82 cases (92.1%).

CONCLUSIONS

Used in complex cases with proximal distorted femurs, the Wagner Cone stem demonstrated a low complication rate, a high-rate consistent adaptive bone remodeling, excellent clinical results, and midterm survival. It is a safe, reliable and advantageous option in complex primary THA. However, the contribution of the underlying cause of the secondary osteoarthritis on the long-term survival of the stem remains to be demonstrated.

LEVEL OF EVIDENCE

IV; retrospective study.

Influence of Tantalum Addition on the Corrosion Passivation of Titanium-Zirconium Alloy in Simulated Body Fluid

Ti-15%Zr alloy and Ti-15%Zr-2%Ta alloy were fabricated to be used in biomedical applications. The corrosion of these two alloys after being immersed in simulated body fluid for 1 h and 72 h was investigated. Different electrochemical methods, including polarization, impedance, and chronoamperometric current with time at 400 mV were employed. Also, the surface morphology and the compositions of its formed film were reported by the use of scanning electron microscope and energy dispersive X-ray. Based on the collected results, the presence of 2%Ta in the Ti-Zr alloy passivated its corrosion by minimizing its corrosion rate. The polarization curves revealed that adding Ta within the alloy increases the corrosion resistance as was confirmed by the impedance spectroscopy and current time data. The change of current versus time proved that the addition of Ta reduces the absolute current even at high anodic potential, 400 mV. The results of both electrochemical and spectroscopic methods indicated that pitting corrosion does not occur for both Ti-Zr and Ti-Zr-Ta alloys, even after their immersion in SBF solutions for 72 h.

Alloy Design and Fabrication of Duplex Titanium-Based Alloys by Spark Plasma Sintering for Biomedical Implant Applications

Very often, pure Ti and (α + β) Ti-6Al-4V alloys have been used commercially for implant applications, but ensuring their chemical, mechanical, and biological biocompatibility is always a serious concern for sustaining the long-term efficacy of implants. Therefore, there has always been a great quest to explore new biomedical alloying systems that can offer substantial beneficial effects in tailoring a balance between the mechanical properties and biocompatibility of implantable medical devices. With a view to the mechanical performance, this study focused on designing a Ti-15Zr-2Ta-xSn (where x = 4, 6, 8) alloying system with high strength and low Young's modulus prepared by a powder metallurgy method. The experimental results showed that mechanical alloying, followed by spark plasma sintering, produced a fully consolidated (α + β) Ti-Zr-Ta-Sn-based alloy with a fine grain size and a relative density greater than 99%. Nevertheless, the shape, size, and distribution of α-phase precipitations were found to be sensitive to Sn contents. The addition of Sn also increased the α/β transus temperature of the alloy. For example, as the Sn content was increased from 4 wt.% to 8 wt.%, the β grains transformed into diverse morphological characteristics, namely, a thin-grain-boundary α phase (α_GB), lamellar α colonies, and acicular α_s precipitates and very low residual porosity during subsequent cooling after the spark plasma sintering procedure, which is consistent with the relative density results. Among the prepared alloys, Ti-15Zr-2Ta-8Sn exhibited the highest hardness (s340 HV), compressive yield strength (~1056 MPa), and maximum compressive strength (~1470). The formation of intriguing precipitate-matrix interfaces (α/β) acting as dislocation barriers is proposed to be the main reason for the high strength of the Ti-15Zr-2Ta-8Sn alloy. Finally, based on mechanical and structural properties, it is envisaged that our developed alloys will be promising for indwelling implant applications.

Comparative Investigation of the Influence of Ultrafine-Grained State on Deformation and Temperature Behavior and Microstructure Formed during Quasi-Static Tension of Pure Titanium and Ti-45Nb Alloy by Means of Infrared Thermography

A comprehensive study was performed of the deformation and temperature behavior during quasi-static tension, as well as the peculiarities of accumulation and dissipation of energy during plastic deformation. Microstructural analysis at the pre-fracture stage of pure titanium and Ti-45Nb alloy in the coarse grain (CG) and ultrafine-grained (UFG) states was also conducted. It was shown that substructural and dispersion hardening leads to a change in the regularities of dissipation and accumulation energies during deformation of the samples of the pure titanium and Ti-45Nb alloy in the UFG state. Some features of structural transformations during deformation of the pure titanium and Ti-45Nb alloy samples in the CG and UFG states were studied. A band and cellular-network and fragmented dislocation structure was formed in the case of the CG state, while large anisotropic fragments were formed in the UFG state, thus specifying a local softening of the material before fracture.

Influence of Solid Loading on the Gel-Casting of Porous NiTi Alloys

Porous NiTi alloys are widely applied in the field of medical implant materials due to their excellent properties. In this paper, porous NiTi alloys were prepared by non-aqueous gel-casting. The influence of solid loading on the process characteristics of slurries and the microstructure and mechanical properties of sintered samples were investigated. The viscosity and the stability of slurry significantly increased with the growth of solid loading, and the slurry had better process characteristics in the solid loading range of 40-52 vol.%. Meanwhile, the porosity and average pore diameter of the sintered NiTi alloys decreased with a rise in the solid loading, while the compressive strength increased. Porous NiTi alloys with porosities of 43.3-48.6%, average pore sizes of 53-145 µm, and compressive strengths of 87-167 MPa were fabricated by gel-casting. These properties meet the requirements of cortical bone. The results suggest that the pore structure and mechanical properties of porous NiTi products produced by gel-casting can be adjusted by controlling the solid loading.

Effect of Cooling and Annealing Conditions on the Microstructure, Mechanical and Superelastic Behavior of a Rotary Forged Ti-18Zr-15Nb (at. %) Bar Stock for Spinal Implants

In this work, the microstructure, phase state, texture, superelastic and mechanical properties of a Ti-18Zr-15Nb (at. %) shape memory alloy subjected to a combined thermomechanical treatment, including hot rotary forging with either air cooling or water quenching and post-deformation annealing are studied. It was revealed that the main structural component of the deformed and annealed alloy is BCC β-phase. With an increase in the forging temperature from 600 to 700 °C, the average grain size increases from 5.4 to 17.8 µm for the air-cooled specimens and from 3.4 to 14.7 µm for the water-quenched specimens. Annealing at 525 °C after forging at 700 °C with water quenching leads to the formation of a mixed statically and dynamically polygonized substructure of β-phase. In this state, the alloy demonstrates the best combination of functional properties in this study: a Young's modulus of ~33 GPa, an ultimate tensile strength of ~600 MPa and a superelastic recovery strain of ~3.4%.

Laser-Deposited Beta Type Ti-42Nb Alloy with Anisotropic Mechanical Properties for Pioneering Biomedical Implants with a Very Low Elastic Modulus

Present commercial titanium alloy implants have an elastic modulus higher than 100 GPa, whereas that of the cortical bone is much smaller (17−28 GPa). This elastic modulus mismatch produces a stress shielding effect and the resorption of the bone surrounding the implant. In the present work, a <100> fiber texture is developed in β type Ti-42Nb (wt%) alloy ingots generated by laser-directed energy deposition (LDED) in order to achieve anisotropic mechanical properties. In addition, we demonstrate that laser-deposited β type Ti-42Nb alloy ingots with an intense <100> fiber texture exhibit a very low elastic modulus in the building direction (Ez < 50 GPa) and high yield (σ0.2z > 700 MPa) and tensile (UTSz > 700 MPa) strengths. Laser-deposited Ti-42Nb alloy enhances the osteoinductive effect, promoting the adhesion, proliferation, and spreading of human osteoblast-like cells. Hence, we propose that laser-deposited β type Ti-42Nb alloy is a potentially promising candidate for the manufacturing of pioneering biomedical implants with a very low elastic modulus that can suppress stress shielding.

Optimal microstructure and mechanical properties of open-cell porous titanium structures produced by selective laser melting

Three-dimensional printing technology enables the production of open cell porous structures. This has advantages but not only in terms of weight reduction. In implant structures, the process of osseointegration is improved, mechanical integration is better, the open cell porous structures resemble a trabecular structure that mimics bone tissue. In this work, we investigated titanium structures made porous by cutting spheres. Based on the patterns of different types of crystal models we created porosity with different strategies. We have shown that there are significant differences in mechanical properties between the porous structures formed with different strategies. We determined the structure that loses the least load-bearing capacity compared to the solid structure, with the same porosity levels and mechanical stresses. We characterized the possibility location and environment of becoming an open cell structure. We performed the calculations with mechanical simulations, which were validated experimentally. The quality of the three-dimensional printing of samples was checked by computed tomography reconstruction analysis.

Comparative Study of Biotin and Hydroxyapatite on Biological Properties of Composite Coating

The ultimate goal of using biomaterials is to improve human health by restoring the function of natural living tissues and organs in the body. The present work aims to modify the composite coating layer properties by using two different types of bioactive reinforcing materials (biotin and hydroxyapatite) particles in different percentages (5% and 10%). Coatings were applied onto commercially pure Ti, SS 316 L, and SS 304 substrates by the dip-coating method. Characterization of samples includes microstructure observation by field emission scanning electron microscopy (FE-SEM), contact angle measurement (wettability), and MTT. The results show the addition of metallic particles (bioparticles) (hydroxyapatite particles, biotin) at 5 Vol. % improved the whole properties of composite materials. Using different particles' scale size aids to enhance the combinations in the alginate matrix producing a dual effect on composite film properties. In addition, the inclusion of metallic particles has to increase the wettability by reducing the contact angle. At the same time, MTT graphs revealed that after 3 days of exposure in MG-63 cells, 316 L SS alloys' surface following pack adhesion became more active.

Progress in partially degradable titanium-magnesium composites used as biomedical implants

Titanium-magnesium composites have gained increasing attention as a partially degradable biomaterial recently. The titanium-magnesium composite combines the bioactivity of magnesium and the good mechanical properties of titanium. Here, we discuss the limitations of conventional mechanically alloyed titanium-magnesium alloys for bioimplants, in addition we summarize three suitable methods for the preparation of titanium-magnesium composites for bioimplants by melt: infiltration casting, powder metallurgy and hot rotary swaging, with a description of the advantages and disadvantages of all three methods. The titanium-magnesium composites were comprehensively evaluated in terms of mechanical properties and degradation behavior. The feasibility of titanium-magnesium composites as bio-implants was reviewed. In addition, the possible future development of titanium-magnesium composites was discussed. Thus, this review aims to build a conceptual and practical toolkit for the design of titanium-magnesium composites capable of local biodegradation.

Synthesis of Ti6Al4V/SrFHA Composites by Microwave-Assisted Liquid Phase Deposition and Calcination

The feasibility of synthesis of Ti6Al4V/SrFHA (Ca_9.37Sr_0.63(PO₄)₆F₂) composites via coating strontium and fluorine co-doped HA to Ti6Al4V substrate by microwave-assisted liquid phase deposition and calcination was evaluated, with a focus on the effect of the deposition temperature from 30 °C to 70 °C. The outcomes demonstrate that strontium and fluorine can be successfully doped into HA to form a SrFHA coating with modified micromorphology which is deposited on the alloy. When the deposition temperature was 50 °C, the coating with the largest uniform continuous SrFHA coverage was obtained. After calcination, the adhesion strength and Vickers microhardness of the Ti6Al4V/SrFHA composite increased from 0.68 MPa and 323 HV to 2.41 MPa and 329 HV, respectively, with a decrease in the water contact angle from 10.88° to 7.24°, exhibiting enhancement of both mechanical properties and wettability. Moreover, the composite obtained at the deposition temperature of 50 °C exhibited good bioactivity based on the simulate body fluid (SBF) test. On account of the above features primarily as a result of the combined effect of the co-doping of strontium and fluorine, high crystallinity of SrFHA, large surface roughness, and formation of the titanium oxide transition layer, the Ti6Al4V/SrFHA composite shows great potential in dental implantology.

Additively manufactured metallic biomaterials

Metal additive manufacturing (AM) has led to an evolution in the design and fabrication of hard tissue substitutes, enabling personalized implants to address each patient's specific needs. In addition, internal pore architectures integrated within additively manufactured scaffolds, have provided an opportunity to further develop and engineer functional implants for better tissue integration, and long-term durability. In this review, the latest advances in different aspects of the design and manufacturing of additively manufactured metallic biomaterials are highlighted. After introducing metal AM processes, biocompatible metals adapted for integration with AM machines are presented. Then, we elaborate on the tools and approaches undertaken for the design of porous scaffold with engineered internal architecture including, topology optimization techniques, as well as unit cell patterns based on lattice networks, and triply periodic minimal surface. Here, the new possibilities brought by the functionally gradient porous structures to meet the conflicting scaffold design requirements are thoroughly discussed. Subsequently, the design constraints and physical characteristics of the additively manufactured constructs are reviewed in terms of input parameters such as design features and AM processing parameters. We assess the proposed applications of additively manufactured implants for regeneration of different tissue types and the efforts made towards their clinical translation. Finally, we conclude the review with the emerging directions and perspectives for further development of AM in the medical industry.

Effect of Alloying Elements on the Compressive Mechanical Properties of Biomedical Titanium Alloys: A Systematic Review

Due to problems such as the stress-shielding effect, strength-ductility trade-off dilemma, and use of rare-earth, expensive elements with high melting points in Ti alloys, the need for the design of new Ti alloys for biomedical applications has emerged. This article reports the effect of various alloying elements on the compressive mechanical performance of Ti alloys for biomedical applications for the first time as a systematic review following the PRISMA (Preferred Reporting Items for Systematic Reviews and Meta-Analyses) guidelines on this subject. The search strategy in this systematic review used Scopus, Web of Science, and PubMed databases and searched the articles using (Beta-type OR β) AND Titanium AND (Mechanical property OR Microstructure) AND Alloying element keywords. Original articles from 2016 to 2022 published in English have been selected for this study as per the inclusion criteria. The results have shown that Nb can be used as the primary alloying element with Ti as it is a strong β-stabilizer element which also reduces the elastic modulus of Ti alloys. The β-eutectic elements (Fe, Cr, and Mn) have also emerged as cost-effective alloying elements that could improve the mechanical performance of Ti alloys. Ti-Nb-Zr-Ta alloyed with Si has shown potential to withstand the strength-ductility trade-off dilemma. The combination of a Ti-Nb binary alloy has emerged as an attractive material for designing low elastic modulus Ti alloys. The mechanical performance of the Ti-Nb alloy can be further improved using the β-eutectic (Fe, Cr, and Mn) and neutral (Zr, Sn) elements to be alloyed with a Ti-Nb binary alloy. The strength-ductility trade-off issue can be overcome using Si as an alloying element in Ti-Nb-Zr-Ta alloys.

In-Vitro Phenotypic Response of Human Osteoblasts to Different Degrees of Titanium Surface Roughness

Objectives: This study aimed to investigate human osteoblast (HOB) responses towards different degrees of titanium (Ti) implant surface roughness. Methods: Four degrees of Ti surface roughness were investigated on a micrometer roughness scale: smooth (S: 0.08−0.1 µm), minimally rough (MM: 0.3−0.5 µm), moderately rough (MR: 1.2−1.4 µm), and rough (R: 3.3−3.7 µm). HOB cells were cultured, expanded, and maintained according to the supplier’s protocol. Cell proliferation and cytotoxicity were assessed at day 1, 3, 5, and 10 using alamarBlue and lactate dehydrogenase colorimetric assays. Data were analyzed with one-way ANOVA, two-way ANOVA, and Tukey’s post hoc test (p = 0.05 for all tests). Results: There was no significant difference in the cell proliferation or cytotoxicity of the HOB cells in contact with the different degrees of Ti surface roughness. There was, however, a significant time effect on cell proliferation (p < 0.0001) with different exposure durations for each roughness degree. Furthermore, a positive correlation (non-significant) between proliferation and cytotoxicity was observed for all investigated degrees of surface roughness. Conclusion: All investigated roughness degrees showed comparable HOB proliferation, with the MR surface presenting the highest percentage, followed by the R, MM, ad S, surfaces, respectively. The S surface showed the highest cytotoxic effect on HOBs; however, it did not reach the cytotoxic level suggested by the ISO for any medical device to be considered cytotoxic.

In vivo study of dual functionalized mussel-derived bioactive peptides promoting 3D-printed porous Ti6Al4V scaffolds for repair of rabbit femoral defects

The 3D printed porous titanium alloy scaffolds are beneficial to enhance angiogenesis, osteoblast adhesion, and promote osseointegration. However, titanium alloys are biologically inert, which makes the bond between the implant and bone tissue weak and prone to loosening. Inspired by the natural biological marine mussels, we designed four-claw-shaped mussel-derived bioactive peptides for the decoration of porous titanium alloy scaffolds: adhesion peptide-DOPA, anchoring peptide-RGD and osteogenic-inducing peptide-BMP-2. And the bifunctionalization of 3D-printed porous titanium alloy scaffolds was evaluated in vivo in a rabbit model of bone defect with excellent promotion of osseointegration and mechanical stability. Our results show that the in vivo osseointegration ability of the modified 3D printed porous titanium alloy test piece is significantly improved, and the bifunctional polypeptide coating group E has the strongest osseointegration ability. In conclusion, our experimental design partially solves the problems of stress shielding effect and biological inertness, and provides a convenient and feasible method for the clinical application of titanium alloy implants in biomedical implant materials.

Effect of Molybdenum Content on Microstructure and Mechanical Properties of Ti-Mo-Fe Alloys by Powder Metallurgy

Titanium has many limitations in coverage and frequency of application due to its expensive alloying elements and complex manufacturing process. The biocompatible Ti-Mo-Fe ternary beta titanium alloys were designed by replacing high-cost beta-stabilizer elements (V, Nb, Zr, etc.) with low-cost Mo and Fe elements. In addition, it was attempted to obtain a low-cost, high-strength beta-titanium alloy with 800 MPa or more by applying the powder metallurgy process technology to the Ti-Mo-Fe alloy system. The added Mo element has the effect of reducing the elastic modulus of the titanium alloy without reducing its strength. In this study, Ti-Mo-Fe alloys designed with different Mo contents were fabricated using a powder metallurgy process and analyzed in connection with microstructural properties, phase changes, and mechanical properties. As Mo contents are increased, the α-lath thickness of Widmanstätten decreases and the size of prior β grain decreases. It was confirmed that the hardness and tensile strength were excellent and were compared with the ingot material of the same alloy system.