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The high rate of rejection and failure of orthopedic implants is primarily attributed to incomplete osseointegration and stress at the implant-to-bone interface due to significant differences in the mechanical properties of the implant and the surrounding bone. Various surface treatments have been developed to enhance the osteoconductive properties of implants. The aim of this work was the in vitro characterization of titanium alloy modified with a nanocrystalline hydroxyapatite surface layer in relative comparison to unmodified controls. This investigation focused on the behavior of the surface treatment in relation to the physiological environment. Moreover, the osteogenic response of human osteoblasts and adipose stem cells was assessed. Qualitative characterization of cellular interaction was performed via confocal laser scanning microscopy focusing on the cell nuclei and cytoskeletons. Filipodia were assessed using scanning electron microscopy. The results highlight that the HA treatment promotes protein adhesion as well as gene expression of osteoblasts and stem cells, which is relevant for the inorganic and organic components of the extracellular matrix and bone. In particular, cells grown onto HA-modified titanium alloy are able to promote ECM production, leading to a high expression of collagen I and non-collagenous proteins, which are crucial for regulating mineral matrix formation. Moreover, they present an impressive amount of filipodia having long extensions all over the test surface. These findings suggest that the HA surface treatment under investigation effectively enhances the osteoconductive properties of Ti6Al4V ELI. [ABSTRACT FROM AUTHOR]

The high rate of rejection and failure of orthopedic implants is primarily attributed to incomplete osseointegration and stress at the implant-to-bone interface due to significant differences in the mechanical properties of the implant and the surrounding bone. Various surface treatments have been developed to enhance the osteoconductive properties of implants. The aim of this work was the in vitro characterization of titanium alloy modified with a nanocrystalline hydroxyapatite surface layer in relative comparison to unmodified controls. This investigation focused on the behavior of the surface treatment in relation to the physiological environment. Moreover, the osteogenic response of human osteoblasts and adipose stem cells was assessed. Qualitative characterization of cellular interaction was performed via confocal laser scanning microscopy focusing on the cell nuclei and cytoskeletons. Filipodia were assessed using scanning electron microscopy. The results highlight that the HA treatment promotes protein adhesion as well as gene expression of osteoblasts and stem cells, which is relevant for the inorganic and organic components of the extracellular matrix and bone. In particular, cells grown onto HA-modified titanium alloy are able to promote ECM production, leading to a high expression of collagen I and non-collagenous proteins, which are crucial for regulating mineral matrix formation. Moreover, they present an impressive amount of filipodia having long extensions all over the test surface. These findings suggest that the HA surface treatment under investigation effectively enhances the osteoconductive properties of Ti6Al4V ELI.

Introduction: The use of Ti6Al4V for orthopedic implants though widely accepted, is 10X stiffer than bone, that leads to stress shielding and aseptic loosening. Further, oral delivery demands significantly large dosage of drugs. To address these twin challenges, we have fabricated open cell porous scaffolds capable of sustained dual drug delivery. Drug delivery from open cell porous Ti6Al4V implants is a promising approach for in situ delivery in orthopedic and dental implant applications. Methodology: In this study, selective laser melting technology was used to fabricate open cell porous Ti6Al4V ELI scaffolds of 50 % volume fractions with Neovius architecture (NOCL). Electrochemical anodization was used to create micro and nano scale surface features for efficient drug loading. The two payloads: an osteogenic agent (Baicalein) and an anti-cancerous drug (Paclitaxel) were then loaded to different levels for differential release. An osteogenic agent was loaded in the nano reservoirs while paclitaxel was mixed with poloxamer and coated over the scaffold. Results: The mechanical stiffness of the designed NOCL lattices is approximately 1.29 ± 0.05 GPa, which is comparable to the human bone. This helps to reduce stress shielding effect. The scaffolds loaded with baicalein and paclitaxel yielded a sustained drug release profiles, releasing 57 % and 79 % of the pharmaceuticals over a 7-day period, respectively. Additionally, the baicalein-loaded nano reservoirs promote osteoblast differentiation in mesenchymal stem cells. As a result, bio-inspired 3D-printed open cell porous titanium scaffolds loaded with dual drugs offer a workable solution to the problems associated with orthopedic implants.

The long‐term success of intraosseous transcutaneous amputation prostheses (ITAPs) mainly relies on dermal attachment of skin cells to the implant. Otherwise, bacteria can easily penetrate through the interface between the implant and the skin. Therefore, infection at this implant/skin interface remains a significant complication in orthopedic surgeries in which these prostheses are required. Two main strategies were investigated to prevent these potential infection problems which consist in either establishing a strong sealing at the skin/implant interface or on eradicating infections by killing bacteria. In this work, two adhesion peptides, either KRGDS or KYIGSR and one antimicrobial peptide, Magainin 2 (Mag 2), were covalently grafted via phosphonate anchor arms to the surface of the Ti6Al4V ELI (extra low interstitials) material, commonly used to manufacture ITAPs. X‐ray photoelectron spectroscopy, contact angle, and confocal microscopy analyses enabled to validate the covalent and stable grafting of these three peptides. Dermal fibroblasts cultures on bare Ti6Al4V ELI surfaces and functionalized ones displayed a good cell adhesion and proliferation on all samples. However, cell spreading and viability appeared to be improved on grafted surfaces, especially for those conjugated with KRGDS and Mag 2. Moreover, the dermal sheet attachment, was significantly higher on surfaces functionalized with Mag 2 as compared to the other surfaces. Therefore, the surface functionalization with the antimicrobial peptide Mag 2 seems to be the best approach for the targeted application, as it could play a dual role, inducing a strong skin adhesion while limiting infections on Ti6Al4V ELI materials. [ABSTRACT FROM AUTHOR]

Ti6Al4V ELI is a titanium alloy that is quite widely used in medical applications for prosthesis implants. Ti6Al4V ELI has high corrosion resistance and good biocompatibility, but is less bioactive for new bone growth sites. Improving the bioactive properties of titanium alloys can be undertaken by coating them with hydroxyapatite. In this study, the type of hydroxyapatite used is a natural hydroxyapatite which is processed from local Indonesian ingredients, namely white barramundi fish scales (Lates calcarifer). White barramundi scales are a type of waste that contains high calcium, so they have the potential to be a source of hydroxyapatite. The purpose is to determine the characteristics of the natural hydroxyapatite layer on the mechanical properties and surface properties of the Ti6Al4V ELI titanium alloy. The hydroxyapatite coating was conducted by the dip coating method with a coating time of 10, 14, 24, and 30 seconds. The characterisation was carried out using a Stereo Microscope and SEM. The results showed that the hydroxyapatite layer met the thickness parameters in biomedical applications in 14 minutes with a layer thickness of 199 μm. This result is better than previous studies using the electrophoretic deposition method at a voltage of 7 V for 10 seconds where the layer thickness was 72 μm. This indicates that such a simple method of dip coating with an optimum parameter is applicable for coating titanium alloys with a natural hydroxyapatite.

In powder bed fusion laser beam (PBF-LB), powder reusability remains key to keeping cost-effectivity as well as sustainability. In this study, highly sensitive Ti6Al4V ELI powder typically used for medical and aerospace applications is studied. Powder properties of new and reused powders after 10 build cycles subjected to variations such as morphology, particle size distribution (PSD), chemical composition and flowability were analysed. The flow rate using Carney flowmeter increased from 6.8 s to 12 s. Oxygen content slightly increased from 0.11% to 0.12%. The dimensional deviations are measured in six builds of eight samples spread through the build plate. The density of the cubes does not show relevant differences in density (from 99.6% to 99.9%), only the last batch exhibits slightly lower density than the previous builds. Studied properties for the powder and builds are maintained throughout the experiment, demonstrating repeatability of industrial production of metal parts. [ABSTRACT FROM AUTHOR]

The inflammation around poorly osseointegrated bioimplant is one of the root causes of its failure. Therefore, the biomedical industry constantly strives for new ways to develop bioactive surfaces in permanent implants to enhance the service life. In this regard, implant surface modification at micro/nanoscales is carried out to enrich substrate with higher engineering attributes and biocompatibility. Considering the complexities of post-processing of implants, this study evaluates the potentiality of an integrated process of implant machining and surface modification, namely, powder-mixed electric discharge machining (PMEDM). Ti6Al4V ELI implant material, as substrate, is machined under two distinct (Si, SiC) mixed additive conditions using a full factorial design of experiments. The surface quality, surface morphology, recast layer depth, surface chemistry, and work hardening have been holistically investigated. The bioactivity analysis of machined surfaces shows more porosity in the case of Si powder particles (200 to 400 nm) compared to SiC (100 to 250 nm). Furthermore, the study optimized the process parameters for minimum roughness and recast layer depth considering 5 g/L powder concentration, 5A pulse current, 50 µs pulse on time for Si, and 100 µs pulse on time for SiC. A comprehensive review of surface features based on process physical science is established, and nanoscale surface topography influencing protein absorption is analyzed. [ABSTRACT FROM AUTHOR]

This article investigates the effect of cutting parameters on the surface roughness and flank wear during machining of titanium alloy Ti-6Al-4V ELI( Extra Low Interstitial) in minimum quantity lubrication environment by using PVD TiAlN insert. Full factorial design of experiment was used for the machining 2 factors 3 levels and 2 factors 2 levels. Turning parameters studied were cutting speed (50, 65, 80 m/min), feed (0.08, 0.15, 0.2 mm/rev) and depth of cut 0.5 mm constant. The results show that 44.61 % contribution of feed and 43.57 % contribution of cutting speed on surface roughness also 53.16 % contribution of cutting tool and 26.47 % contribution of cutting speed on tool flank wear. Grey relational analysis and TOPSIS method suggest the optimum combinations of machining parameters as cutting speed: 50 m/min, feed: 0.8 mm/rev., cutting tool: PVD TiAlN, cutting fluid: Palm oi

Owing to the possibility of direct processing of CAD models into three-dimensional objects, additive manufacturing (AM) is widely used in the production of individualized bone scaffolds that can lead to perfect restoration of anatomical structures of missing bone tissues. In this work, one of the AM technologies was applied, referred to as Electron Beam Melting (EBM), using Ti6Al4V ELI alloy to produce open-cell structures. Scaffold architecture influences its mechanical properties and is important from the point of view of biological considerations. To optimize mechanical properties, designed geometries were subjected to Finite Element Method analysis and experimental static compression tests. Also, geometric CT analysis of manufactured scaffolds was carried out (geometry deviations up to ± 300 µm). Obtained results have shown that AM can be used to produce Ti6Al4V ELI alloy scaffolds displaying mechanical parameters similar to those of bone tissue (E = 0.45–2.88 MPa). The EBM process affects the microstructure and macrostructural properties of manufactured parts, e.g., through internal porosities present in the material by to unmelted powder particles (internal porosity in range of 1.25–2.25%). To assess the quality and suitability of additively manufactured implants, a multidimensional verification of the impact of the manufacturing process on the properties of the final product was performed. [ABSTRACT FROM AUTHOR]

[Display omitted] • Designed and fabricated Neovius metal lattices that closely emulate the mechanical properties of bone. • A dual drug delivery system was strategized to enhance osteogenic and anti-cancerous activity. • Baicalein (drug 2), an osteogenic agent was intricately loaded into nanostructures on the surface of Neovius lattices. • Paclitaxel (drug 1), an anti-cancerous drug was embedded in the polymer coating that enveloped the entire surface. • Osteogenic and anti-cancerous activities of the fabricated Neovius lattices were validated via in vitro studies. The use of Ti6Al4V for orthopedic implants though widely accepted, is 10X stiffer than bone, that leads to stress shielding and aseptic loosening. Further, oral delivery demands significantly large dosage of drugs. To address these twin challenges, we have fabricated open cell porous scaffolds capable of sustained dual drug delivery. Drug delivery from open cell porous Ti6Al4V implants is a promising approach for in situ delivery in orthopedic and dental implant applications. In this study, selective laser melting technology was used to fabricate open cell porous Ti6Al4V ELI scaffolds of 50 % volume fractions with Neovius architecture (NOCL). Electrochemical anodization was used to create micro and nano scale surface features for efficient drug loading. The two payloads: an osteogenic agent (Baicalein) and an anti-cancerous drug (Paclitaxel) were then loaded to different levels for differential release. An osteogenic agent was loaded in the nano reservoirs while paclitaxel was mixed with poloxamer and coated over the scaffold. The mechanical stiffness of the designed NOCL lattices is approximately 1.29 ± 0.05 GPa, which is comparable to the human bone. This helps to reduce stress shielding effect. The scaffolds loaded with baicalein and paclitaxel yielded a sustained drug release profiles, releasing 57 % and 79 % of the pharmaceuticals over a 7-day period, respectively. Additionally, the baicalein-loaded nano reservoirs promote osteoblast differentiation in mesenchymal stem cells. As a result, bio-inspired 3D-printed open cell porous titanium scaffolds loaded with dual drugs offer a workable solution to the problems associated with orthopedic implants. [ABSTRACT FROM AUTHOR]

The interplay between a prosthetic and tissue represents an important factor for the fixation of orthopedic implants. Laser texturing tests and electropolishing were performed on two materials used in the fabrication of medical devices, i.e., CoCr and Ti6Al4V-ELI alloys. The material surface was textured with a diode-pumped solid state (DPSS) laser and its effect on the surface quality and material modification, under different combinations of laser power and marking speed, were investigated. Our results indicate that an increment of energy per unit length causes an incremental trend in surface roughness parameters. Additionally, phase transformation on the surface of both alloys was achieved. Chemical analysis by energy dispersive X-ray spectrometer (EDX) shows the formation of (Co(Cr,Mo)) phase and the M23C6 precipitate on the CoCr surface; while quantitative analysis of the X-ray diffractometer (XRD) results demonstrates the oxidation of the Ti alloy with the formation of Ti2O and Ti6O from the reduction of the α-Ti phase. The behaviors were both related with an increase of the energy per unit length. Control of the final surface roughness was achieved by an electropolishing post-treatment, minimizing the as-treated values. After polishing, a reduction of surface roughness parameters was obtained in a range between 3% and 44%, while no changes in chemical composition or present phases were observed.

The oxidation behavior of Ti6Al4V ELI alloy subjected to surface severe plastic deformation (SSPDed) is compared to its solution annealed (SAed) counterpart in Ar + 20 % O 2 atmosphere at 500 °C. Moreover, the corrosion performance of oxidized SAed and SSPDed samples is examined in the Ringer solution. The significantly increased presence of high-diffusivity paths, specifically dislocations and grain boundaries (GBs), on the surface of SSPDed sample facilitates the diffusion of oxygen anions and scale-forming elements toward the oxidation front. The SSPDed sample shows a superior oxidation performance due to the rapid formation of a three-layered oxide scale (consisting of an outer Al-rich, an intermediate Ti-rich, and an inner Al-rich oxide layer) on its surface. In contrast to the SAed sample, the SSPDed displays inner and outer Al-rich oxide layers that are more uniform and virtually continuous. The study proposes a physical model that attributes the improved high temperature oxidation and enhanced corrosion resistance of oxidized SSPDed samples to the latter Al-rich inner oxide layer. • Effect of SSPD on the thermal oxidation (TO) behavior of Ti6Al4V ELI alloy is investigated. • Ultrafine grains of ∼62 nm are developed in the topmost surface layer after SSPD. • SSPD modifies the diffusion regime of ionic species during thermal oxidation. • Continuous Al-rich inner layer in the TO-treated SSPDed Ti6Al4V ELI enhances its corrosion and oxidation resistance. • Schematic models are presented to describe the oxidation mechanism. [ABSTRACT FROM AUTHOR]

This paper investigates the effect of cutting parameters on the surface roughness and cutting force of titanium alloy Ti-6Al-4V ELI when turning using PVD TiAlN coated tool in dry environment. Taguchi L9 orthogonal array design of experiment was used for the turning experiment 2 factors and 3 levels. Turning parameters studied were cutting speed (50, 65, 80 m/min), feed rate (0.08, 0.15, 0.2 mm/rev) and depth of cut 0.5 mm constant. Linear and second order model of the surface roughness and cutting force has been developed in terms of cutting speed and feed. The results show that the feed rate was the most impact factor controlling the cutting force and surface roughness produced. MINITAB 17software was used to develop a linear and second order model of surface roughness and cutting force. Optimum condition was at 66.97 m/min of cutting speed, 0.08 mm/rev of feed rate. Surface roughness 0.57μm and cutting force 54.02 N were obtained at the optimum condition. A good agreement between the experimental and predicted surface roughness and cutting force were observed.

Electron beam melting (EBM) is an additive manufacturing technique, which allows forming customized implants that perfectly fit the loss of the anatomical structure of bone. Implantation efficiency depends not only on the implant’s functional or mechanical properties but also on its surface properties, which are of great importance with regard to such biological processes as bone regeneration or microbial contamination. This work presents the impact of surface modifications (mechanical polishing, sandblasting, and acid-polishing) of EBM-produced Ti6Al4V ELI implants on essential biological parameters. These include wettability, cytotoxicity toward fibroblast and osteoblast cell line, and ability to form biofilm by Staphylococcus aureus, Pseudomonas aeruginosa, and Candida albicans. Obtained results indicated that all prepared surfaces exhibited hydrophilic character and the highest changes of wettability were obtained by chemical modification. All implants displayed no cytotoxicity against osteoblast and fibroblast cell lines regardless of the modification type. In turn, the quantitative microbiological tests and visualization of microbial biofilm by means of electron microscopy showed that type of implant’s modification correlated with the species-specific ability of microbes to form biofilm on it. Thus, the results of the presented study confirm the relationship between such technological aspects as surface modification and biological properties. The provided data are useful with regard to applications of the EBM technology and present a significant step towards personalized, customized implantology practice.

The surface of orthopaedic bone implants is in most cases formed by porous plasma spray. The introduction of 3D printing into the production of implants has made it possible to replace plasma spray with a trabecular bone-like structure that can be fabricated by 3D printing. The principle is to create a suitable surface porosity for anchoring the implant in the bone and adapting the modulus of elasticity to the bone properties. The elastic behaviour of both the structures can be compared by means of a compression test, but it is not possible to compare the modulus of elasticity at the local sites. The aim of the work was to verify the possibility to use the nanoindentation method for the local testing of the modulus of elasticity. The selected method made it possible to map the so-called reduced modulus of elasticity at the precisely defined places. Specifically, the 3D printed trabecular structure of Ti6Al4V ELI was compared with titanium plasma spraying. The printed structure with a bulk porosity of 77% showed the local modulus of elasticity in the range of 57–97 GPa depending on the test site. In contrast, for the plasma spray with a volume porosity of 28%, the modulus of elasticity was around the average value of 54 GPa. At the same time, the microstructure and chemical composition were analysed at the critical points of the structure crossover or the transition from the bulk material to the trabecular structure. No change in the microstructure or chemical composition was observed. Both structures bring the modulus of elasticity closer to the bone modulus of elasticity, but 3D printing offers more possibilities to modify the elastic behaviour and the shape and pore size as well.

In this work, Ti6Al4V ELI samples were fabricated with previously optimized parameters by selective laser melting (SLM) and then heat-treated under vacuum (HT) or hot isostatic pressed (HIP). Optical microscopy (OM) and scanning electron microscopy (SEM) were used to characterize the microstructure. As-built microstructure was found to be dominated by columnar grains and acicular α′ martensite. Thermo-mechanical treatments allowed to modify the microstructure in the size and shape of the grains, as well in the volume fraction and chemical composition of the phases. Apart from the phase transformation, HIP treatment also allowed to significantly reduce the interior defects, such as pores and internal cracks. Tensile and fatigue properties of the Ti6Al4V ELI samples corresponding to the different microstructures were subsequently investigated. As-built samples exhibited a high tensile strength but a poor ductility with an elongation generally smaller than 6% and low fatigue resistance. HT samples displayed a reduced tensile strength but improved elongation behavior and relatively enhanced fatigue resistance versus as-built samples. The HIP treatment also resulted in a reduction in strength but improved furthermore the ductility and the fatigue behavior due to the elimination of internal defects. [ABSTRACT FROM AUTHOR]

En este trabajo se estudió el comportamiento tribológico, la rigidez y dureza, de la superficie de la aleación Ti6Al4V ELI después de llevar a cabo un tratamiento de nitruración por descarga intensa de plasma a temperaturas de 450, 480 y 520 °C. El par tribológico empleado fue metal- metal (pin de Ti6Al4V ELI - disco de Ti6Al4V ELI con tratamiento) para el respectivo cálculo del coeficiente de fricción. Los ensayos de nanoindentación se realizaron con una punta de ultra alta dureza de módulo de rigidez conocido, que permitió obtener la dureza promedio y el módulo de Young en GPa, de acuerdo con las normas ISO 14577 y ASTM G99-95 respectivamente. Para la caracterización del sustrato, se empleó microscopia electrónica de barrido, microscopia de fuerza atómica y difracción de rayos X, obteniendo así características importantes del comportamiento elástico-plástico, antes y después de aplicarse la nitruración a la aleación por descarga intensa de plasma.

The heat treatment effects on the corrosion behavior of Ti6Al4V ELI fabricated by laser powder bed fusion (LPBF) are revisited, and comprehensive microstructural characterization and statistical electrochemical tests are carried out on the pore-free microelectrodes. Compared with the heat-treated (HT, 950 ℃ for 2 h) LPBF Ti6Al4V counterparts, the as-built LPBF Ti6Al4V ELI exhibits a worse corrosion resistance in fluoride-containing chloride solution. For the LPBF Ti6Al4V ELI, the micro-galvanic potentials between the widmanstätten α and β phases (about 35 mV) encourage the formation of a thicker passive film with more titanium oxides and less cation vacancy than that in the as-built counterparts. Consequently, the as-built LPBF Ti6Al4V shows a rapid metallic dissolution rate and a high sensitivity to localized corrosion in the fluoride-contained environment with a less-protective oxide film. The underlying mechanisms for the heat treatment effects on the degradation behavior of pore-free LPBF Ti6Al4V ELI in fluoride-containing chloride solution are proposed. • Pore-free micro-electrodes and statistical experimental tests are employed. • Thicker passive film with less defect is formed on the 950HT-LPBF TC4 ELI. • As-received LPBF TC4 ELI shows about 1.36 times higher metallic ions loss rate. [ABSTRACT FROM AUTHOR]

In this paper, the effects of cell geometry and relative density on the high-cycle fatigue behavior of Titanium scaffolds produced by selective laser melting and electron beam melting techniques were numerically investigated by finite element analysis. The regular titanium lattice samples with three different unit cell geometries, namely, diamond, rhombic dodecahedron and truncated cuboctahedron, and the relative density range of 0.1–0.3 were analyzed under uniaxial cyclic compressive loading. A failure event based algorithm was employed to simulate fatigue failure in the cellular material. Stress-life approach was used to model fatigue failure of both bulk (struts) and cellular material. The predicted fatigue life and the damage pattern of all three structures were found to be in good agreement with the experimental fatigue investigations published in the literature. The results also showed that the relationship between fatigue strength and cycles to failure obeyed the power law. The coefficient of power function was shown to depend on relative density, geometry and fatigue properties of the bulk material while the exponent was only dependent on the fatigue behavior of the bulk material. The results also indicated the failure surface at an angle of 45° to the loading direction. [ABSTRACT FROM AUTHOR]

One alternative for processing cost reduction with simultaneous improvement of the mechanical properties of the Medical Ti6Al4V alloy is to get its semi-solid feedstock with a non-dendritic microstructure for further processing. The purpose of the present work is to evaluate the possibility of obtaining a semi-solid Ti6Al4V alloy by heating it up from the room temperature to the range temperature between the lines solidus and liquidus, using induction heating. The Ti6Al4V billets underwent heat treatment and quenching for semi-solid formation using a designed device and specific time pulsed profile. The billet temperature reached 1630 oC, and after the cooling rate of 54 oC/s, some samples formed a globular phase characteristic of the semi-solid alloy. This study shows that it is possible to get a semi-solid microstructure of this alloy starting from its solid state. [ABSTRACT FROM AUTHOR]

Meta-materials are structures when their small-scale properties are considered, but behave as materials when their homogenized macroscopic properties are studied. There is an intimate relationship between the design of the small-scale structure and the homogenized properties of such materials. In this article, we studied that relationship for meta-biomaterials that are aimed for biomedical applications, otherwise known as meta-biomaterials. Selective laser melted porous titanium (Ti6Al4V ELI) structures were manufactured based on three different types of repeating unit cells, namely cube, diamond, and truncated cuboctahedron, and with different porosities. The morphological features, static mechanical properties, and fatigue behavior of the porous biomaterials were studied with a focus on their fatigue behavior. It was observed that, in addition to static mechanical properties, the fatigue properties of the porous biomaterials are highly dependent on the type of unit cell as well as on porosity. None of the porous structures based on the cube unit cell failed after 10 6 loading cycles even when the applied stress reached 80% of their yield strengths. For both other unit cells, higher porosities resulted in shorter fatigue lives for the same level of applied stress. When normalized with respect to their yield stresses, the S-N data points of structures with different porosities very well ( R 2 >0.8) conformed to one single power law specific to the type of the unit cell. For the same level of normalized applied stress, the truncated cuboctahedron unit cell resulted in a longer fatigue life as compared to the diamond unit cell. In a similar comparison, the fatigue lives of the porous structures based on both truncated cuboctahedron and diamond unit cells were longer than that of the porous structures based on the rhombic dodecahedron unit cell (determined in a previous study). The data presented in this study could serve as a basis for design of porous biomaterials as well as for corroboration of relevant analytical and computational models. [ABSTRACT FROM AUTHOR]

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Site-specific drug delivery has the potential to reduce drug dosage by 3- to 5-folds. Given the propensity of drugs used in the treatment of tuberculosis and cancers, the increased drug dosages via oral ingestion for several months to a few years of medication is often detrimental to the health of patients. In this study, the sustained delivery of drugs with multiscale structured novel Neovius lattices was achieved. 3D Neovius open cell lattices (NOCL) with porosities of 40%, 45%, and 50% were fabricated layer-by-layer on the laser bed fusion process. Micron-sized Ti 6 Al 4 V ELI powder was used for 3D printing. The Young's modulus achieved from the novel Neovius lattices were in the range of 1.2-1.6 GPa, which is comparable to human cortical bone and helps to improve implant failure due to the stress shielding effect. To provide sustained drug delivery, nanotubes (NTs) were fabricated on NOCLs via high-voltage anodization. The osteogenic agent icariin was loaded onto the NOCL-NT samples and their release profiles were studied for 7 d. A significantly steady and slow release rate of 0.05% per hour of the drug was achieved using NOCL-NT. In addition, the initial burst release of NOCL-NT was 4 fold lower than that of the open-cell lattices without NTs. Cellular studies using MG63 human osteoblast-like cells were performed to determine their biocompatibility and osteogenesis which were analyzed using Calcein AM staining and Alamar Blue after 1, 5, and 7 d. 3D printed NOCL samples with NTs and with Icariin loaded NTs demonstrated a significant increase in cell proliferation as compared to as printed NOCL samples., (© 2022 IOP Publishing Ltd.)

The interplay between a prosthetic and tissue represents an important factor for the fixation of orthopedic implants. Laser texturing tests and electropolishing were performed on two materials used in the fabrication of medical devices, i.e., CoCr and Ti6Al4V-ELI alloys. The material surface was textured with a diode-pumped solid state (DPSS) laser and its effect on the surface quality and material modification, under different combinations of laser power and marking speed, were investigated. Our results indicate that an increment of energy per unit length causes an incremental trend in surface roughness parameters. Additionally, phase transformation on the surface of both alloys was achieved. Chemical analysis by energy dispersive X-ray spectrometer (EDX) shows the formation of (Co(Cr,Mo)) phase and the M23C6 precipitate on the CoCr surface; while quantitative analysis of the X-ray diffractometer (XRD) results demonstrates the oxidation of the Ti alloy with the formation of Ti2O and Ti6O from the reduction of the α-Ti phase. The behaviors were both related with an increase of the energy per unit length. Control of the final surface roughness was achieved by an electropolishing post-treatment, minimizing the as-treated values. After polishing, a reduction of surface roughness parameters was obtained in a range between 3% and 44%, while no changes in chemical composition or present phases were observed. [ABSTRACT FROM AUTHOR]

Electron beam melting (EBM) is an additive manufacturing technique, which allows forming customized implants that perfectly fit the loss of the anatomical structure of bone. Implantation efficiency depends not only on the implant's functional or mechanical properties but also on its surface properties, which are of great importance with regard to such biological processes as bone regeneration or microbial contamination. This work presents the impact of surface modifications (mechanical polishing, sandblasting, and acid-polishing) of EBM-produced Ti6Al4V ELI implants on essential biological parameters. These include wettability, cytotoxicity toward fibroblast and osteoblast cell line, and ability to form biofilm by Staphylococcus aureus, Pseudomonas aeruginosa, and Candida albicans. Obtained results indicated that all prepared surfaces exhibited hydrophilic character and the highest changes of wettability were obtained by chemical modification. All implants displayed no cytotoxicity against osteoblast and fibroblast cell lines regardless of the modification type. In turn, the quantitative microbiological tests and visualization of microbial biofilm by means of electron microscopy showed that type of implant's modification correlated with the species-specific ability of microbes to form biofilm on it. Thus, the results of the presented study confirm the relationship between such technological aspects as surface modification and biological properties. The provided data are useful with regard to applications of the EBM technology and present a significant step towards personalized, customized implantology practice. [ABSTRACT FROM AUTHOR]

• The surface roughness, morphologies, and osseointegration are correlated and discussed. • Irregular and micro-rough surface structures drive the osseointegration on Ti6Al4V ELI. • The additively manufactured screws present the higher bone-to-implant contact and an excellent biomechanical performance. In the present study, the osseointegration of additively manufactured screws with a micro-rough surface structure and conventionally machined Ti6Al4V ELI screws with a smooth surface structure is compared. Screws were implanted in rabbit femurs or tibiae for two weeks. The additively manufactured screws exhibited a micro-rough surface with attached semi-molten powder with a size of 50–100 μm and blunt threads, whereas the conventionally machined screws showed a smooth surface and sharp threads. The bonding strength of the additively manufactured screws was significantly higher than that of the conventionally machined screws. The additively manufactured screws showed higher bone-to-implant contact than the conventionally machined screws. Considerable amount of bone tissue on the surface of the additively manufactured screws remained after the push-out tests, and the rabbit tibiae with the additively manufactured screws were significantly damaged, indicating a higher osseointegration rate. Active osteogenesis was observed around the semi-molten powder of the additively manufactured screws, and new bone was well developed along the micro-rough surface. Overall, this study shows that the micro-rough surface improved the bone ingrowth and suggests that additively manufactured screws may be an alternative to conventionally machined screws. [ABSTRACT FROM AUTHOR]

This paper systematically investigates the biomedical performance of selective laser melted (SLM) porous Ti6Al4V ELI scaffolds for bone implantation through in vitro and in vivo experiments. Scaffolds with pore sizes of 500 μm, 600 μm and 700 μm and porosities of 60% and 70% were manufactured in order to explore the optimum pore size and porosity. Rat bone marrow mesenchymal stem cells (rBMMSCs) were used in the in vitro experiments. Cell Counting Kit-8, live/dead staining and scanning electron microscope were used to assess the cytotoxicity of the porous scaffolds. DNA content quantification was performed to investigate cell proliferation on the porous scaffolds. The osteogenic differentiation of cells was measured by alkaline phosphatase (ALP) activity and osteogenic gene expressions, including bone morphogenetic protein-2 (BMP-2), collagen type 1α1 (COL-1), osteocalcin (OCN), osteopontin (OPN) and runt-related transcription factor-2 (RUNX-2). The Sprague-Dawley (SD) rat models with distal femoral condyles defect were used in the in vivo experiments. Micro-CT analysis and histological analysis were performed after implantation surgery to reveal the bone ingrowth into the porous scaffolds. All in vitro data were analyzed by one-way ANOVA followed by Tukey post hoc tests, in vivo data were analyzed using Kruskall-Wallis ANOVA and Conover-Inman post-hoc test. Based on the in vitro and in vivo experiments, it is found that the porous scaffolds manufactured by SLM did not induce a cytotoxic effect. Among all the porous scaffolds, the scaffold with a pore size of 500 μm and porosity of 60% showed the best cell proliferation and osteogenic differentiation (in vitro experiments) and bone ingrowth (in vivo experiments). • Systematically investigations of SLM Ti6Al4V ELI scaffolds for bone implantation through in vitro and in vivo experiments were conducted. • Based on the in vitro and in vivo experiments, it is found that the SLM scaffolds did not induce a cytotoxic effect. • The SLM scaffold with a pore size of 500μm and porosity of 60% showed the best cell proliferation and osteogenic differentiation and bone ingrowth. [ABSTRACT FROM AUTHOR]