Design and development of metallic biomaterials with biological and mechanical biocompatibility

Selective laser melting of low-alloyed titanium based alloy with a large solidification range

In this work, thermodynamic calculations for α + β Type Ti-Fe-Cu-Sn alloy were carried out by the Thermo-Calc software. Powders from this alloy were obtained by plasma sputtering and used for subsequent 3D printing of experimental samples. The effect of various selective laser melting (SLM) parameters on porosity and hot cracking susceptibility as well as the electrochemical characteristics of the alloy have been studied. The optimal technological regime for the manufacture of samples by the SLM method was determined. It has been established that to obtain relatively dense samples without cracks, regimes with volumetric energy density Ev = 250-300 J/mm3 are required. It has been established that a change in the electrochemical behavior of the Ti94Fe1Cu1Sn4 alloy is related to the formation of a nonequilibrium Ti2Cu phase. Based on the findings we recomended directions for further research.

Investigation on the Microstructure and Mechanical Properties of the Ti-Ta Alloy with Unmelted Ta Particles by Laser Powder Bed Fusion

Titanium-tantalum (Ti-Ta) alloy has excellent biomechanical properties with high strength and low Young's modulus, showing great application potential in the biomedical industry. In this study, Ti-Ta alloy samples were prepared by laser powder bed fusion (LPBF) technology with mixed pure 75 wt.% Ti and 25 wt.% Ta powders as the feedstock. The maximum relative density of Ti-Ta samples prepared by LPBF reached 99.9%. It is well-accepted that four nonequilibrium phases, namely, α', α″ and metastable β phase exist in Ti-Ta alloys. The structure of α', α″ and β are hexagonal close-packed (HCP), base-centered orthorhombic (BCO) and body-centered cubic (BCC), respectively. X-ray Diffraction (XRD) analysis showed that the α' phase transformed to the α″ phase with the increase of energy density. The lamellar α'/α″ phases and the α″ twins were generated in the prior β phase. The microstructure and mechanical properties of the Ti-Ta alloy were optimized with different LPBF processing parameters. The samples prepared by LPBF energy density of 381 J/mm³ had a favorable ultimate strength (UTS) of 1076 ± 2 MPa and yield strength of 795 ± 16 MPa. The samples prepared by LPBF energy density of 76 had excellent ductility, with an elongation of 31% at fracture.

Recent Advances in Decellularized Matrix-Derived Materials for Bioink and 3D Bioprinting

As an emerging 3D printing technology, 3D bioprinting has shown great potential in tissue engineering and regenerative medicine. Decellularized extracellular matrices (dECM) have recently made significant research strides and have been used to create unique tissue-specific bioink that can mimic biomimetic microenvironments. Combining dECMs with 3D bioprinting may provide a new strategy to prepare biomimetic hydrogels for bioinks and hold the potential to construct tissue analogs in vitro, similar to native tissues. Currently, the dECM has been proven to be one of the fastest growing bioactive printing materials and plays an essential role in cell-based 3D bioprinting. This review introduces the methods of preparing and identifying dECMs and the characteristic requirements of bioink for use in 3D bioprinting. The most recent advances in dECM-derived bioactive printing materials are then thoroughly reviewed by examining their application in the bioprinting of different tissues, such as bone, cartilage, muscle, the heart, the nervous system, and other tissues. Finally, the potential of bioactive printing materials generated from dECM is discussed.

Electrochemical and biological characterization of Ti-Nb-Zr-Si alloy for orthopedic applications

The performance of current biomedical titanium alloys is limited by inflammatory and severe inflammatory conditions after implantation. In this study, a novel Ti-Nb-Zr-Si (TNZS) alloy was developed and compared with commercially pure titanium, and Ti-6Al-4V alloy. Electrochemical parameters of specimens were monitored during 1 h and 12 h immersion in phosphate buffered saline (PBS) as a normal, PBS/hydrogen peroxide (H₂O₂) as an inflammatory, and PBS/H₂O₂/albumin/lactate as a severe inflammatory media. The results showed an effect of the H₂O₂ in inflammatory condition and the synergistic behavior of H₂O₂, albumin, and lactate in severe inflammatory condition towards decreasing the corrosion resistance of titanium biomaterials. Electrochemical tests revealed a superior corrosion resistance of the TNZS in all conditions due to the presence of silicide phases. The developed TNZS was tested for subsequent cell culture investigation to understand its biocompatibility nature. It exhibited favorable cell-materials interactions in vitro compared with Ti-6Al-4V. The results suggest that TNZS alloy might be a competitive biomaterial for orthopedic applications.

Phase Transformations Caused by Heat Treatment and High-Pressure Torsion in TiZrHfMoCrCo Alloy

In this work the high-entropy alloy studied contained six components, Ti/Zr/Hf/Mo/Cr/Co, and three phases, namely one phase with body-centered cubic lattice (BCC) and two Laves phases C14 and C15. A series of annealings in the temperature range from 600 to 1000 °C demonstrated not only a change in the microstructure of the TiZrHfMoCrCo alloy, but also the modification of phase composition. After annealing at 1000 °C the BCC phase almost fully disappeared. The annealing at 600 and 800 °C leads to the formation of new Laves phases. After high-pressure torsion (HPT) of the as-cast TiZrHfMoCrCo alloy, the grains become very small, the BCC phase prevails, and C14 Laves phase completely disappears. This state is similar to the state after annealing at high effective temperature T_eff. The additional annealing at 1000 °C after HPT returns the phase composition back to the state similar to that of the as-cast alloy after annealing at 1000 °C. At 1000 °C the BCC phase completely wets the C15/C15 grain boundaries (GBs). At 600 and 800 °C the GB wetting is incomplete. The big spread of nanohardness and Young's modulus for the BCC phase and (C15 + C14) Laves phases is observed.

Ti64/20Ag Porous Composites Fabricated by Powder Metallurgy for Biomedical Applications

We present a novel Ti64/20Ag highly porous composite fabricated by powder metallurgy for biomedical applications and provide an insight into its microstructure and mechanical proprieties. In this work, the Ti64/20Ag highly porous composites were successfully fabricated by the space holder technique and consolidated by liquid phase sintering, at lower temperatures than the ones used for Ti64 materials. The sintering densification was evaluated by dilatometry tests and the microstructural characterization and porosity features were determined by scanning electron microscopy and computed microtomography. Permeability was estimated by numerical simulations on the 3D real microstructure. Mechanical properties were evaluated by simple compression tests. Densification was achieved by interparticle pore filling with liquid Ag that does not drain to the large pores, with additional densification due to the macroscopical deformation of large pores. Pore characteristics are closely linked to the pore formers and the permeability was highly increased by increasing the pore volume fraction, mainly because the connectivity was improved. As expected, with the increase in porosity, the mechanical properties decreased. These results permitted us to gain a greater understanding of the microstructure and to confirm that we developed a promising Ti64/20Ag composite, showing E of 7.4 GPa, σ_y of 123 MPa and permeability of 3.93 × 10^-11 m². Enhanced adaptability and antibacterial proprieties due to Ag were obtained for bone implant applications.

Improved Tribocorrosion Behavior Obtained by In-Situ Precipitation of Ti2C in Ti-Nb Alloy

Novel in-situ Ti-based matrix composites (TMCs) were developed through the reactive hot pressing of Ti + NbC powder blends. Due to the chemical reaction that occurred in the solid-state during processing, the produced samples were composed of an Nb-rich β-Ti phase that formed a metallic matrix along with Ti2C as a reinforcing phase. By employing different proportions of Ti:NbC, the phase composition of the alloys was designed to contain different ratios of α-Ti and β-Ti. The present work investigated the corrosion and tribocorrosion behavior of the composites, compared to unreinforced Ti, in a phosphate-buffered solution (PBS) at body temperature. Corrosion tests included potentiodynamic polarization and electrochemical impedance spectroscopy (EIS). Tribocorrosion tests were carried out using a ball-on-plate tribometer with sliding performed at open circuit potential (OCP) and under anodic potentiostatic conditions. Results showed that the stabilization of the β phase in the matrix led to a decrease in the hardness. However, the formation of the in-situ reinforcing phase significantly improved the tribocorrosion behavior of the composites due to a load-carrying effect, lowering the corrosion tendency and kinetics under sliding. Furthermore, localized corrosion was not observed at the interface between the reinforcing phase and the matrix.

Improved activity of MC3T3-E1 cells by the exciting piezoelectric BaTiO3/TC4 using low-intensity pulsed ultrasound

Developing bioactive materials for bone implants to enhance bone healing and bone growth has for years been the focus of clinical research. Barium titanate (BT) is an electroactive material that can generate electrical signals in response to applied mechanical forces. In this study, a BT piezoelectric ceramic coating was synthesized on the surface of a TC4 titanium alloy, forming a BT/TC4 material, and low-intensity pulsed ultrasound (LIPUS) was then applied as a mechanical stimulus. The combined effects on the biological responses of MC3T3-E1 cells were investigated. Results of scanning electron microscopy, energy-dispersive X-ray spectroscopy, and X-ray diffraction showed that an uniform nanospheres -shaped BT coating was formed on TC4 substrate. Piezoelectric behaviors were observed using piezoelectric force microscopy with the piezoelectric coefficient d33 of 0.42 pC/N. Electrochemical measures indicated that LIPUS-stimulated BT/TC4 materials could produce a microcurrent of approximately 10 μA/cm2. In vitro, the greatest osteogenesis (cell adhesion, proliferation, and osteogenic differentiation) was found in MC3T3-E1 cells when BT/TC4 was stimulated using LIPUS. Furthermore, the intracellular calcium ion concentration increased in these cells, possibly because opening of the L-type calcium ion channels was promoted and expression of the CaV1.2 protein was increased. Therefore, the piezoelectric BT/TC4 material with LIPUS loading synergistically promoted osteogenesis, rending it a potential treatment for early stage formation of reliable bone-implant contact.

Osteosphere Model to Evaluate Cell-Surface Interactions of Implantable Biomaterials

Successful biomaterials for bone tissue therapy must present different biocompatible properties, such as the ability to stimulate the migration and proliferation of osteogenic cells on the implantable surface, to increase attachment and avoid the risks of implant movement after surgery. The present work investigates the applicability of a three-dimensional (3D) model of bone cells (osteospheres) in the evaluation of osteoconductive properties of different implant surfaces. Three different titanium surface treatments were tested: machined (MA), sandblasting and acid etching (BE), and Hydroxyapatite coating by plasma spray (PSHA). The surfaces were characterized by Scanning Electron Microscopy (SEM) and atomic force microscopy (AFM), confirming that they present very distinct roughness. After seeding the osteospheres, cell–surface interactions were studied in relation to cell proliferation, migration, and spreading. The results show that BE surfaces present higher densities of cells, leaving the aggregates towards than titanium surfaces, providing more evidence of migration. The PSHA surface presented the lowest performance in all analyses. The results indicate that the 3D model allows the focal analysis of an in vitro cell/surfaces interaction of cells and surfaces. Moreover, by demonstrating the agreement with the clinical data observed in the literature, they suggest a potential use as a predictive preclinical tool for investigating osteoconductive properties of novel biomaterials for bone therapy.

The effect of composite PHB coating on the biological properties of a magnesium based alloy

Magnesium alloys have been widely investigated as biodegradable cardiovascular temporal implants due to their better mechanical properties and biocompatibility, but the rapid degradation limited its application. In this study, the anodic oxidation-Cu structure was used to improve the adhesive strength and stability between poly-β-hydroxybutyrate (PHB) and magnesium alloys, and the effects of anodic oxidation magnesium alloys with copper film and PHB film (MACP) on human umbilical vein endothelial cells (HUVECs), blood compatibility and antibacterial properties were investigated in this research. As the result, the MACP structure had a stable structure and better corrosion resistance, and significant antibacterial properties. The coating would not affect the original excellent biocompatibility of the magnesium alloy. It was indicated that MACP was a potential surface modification strategy for vascular stents candidate material.

Corrosion and wear behaviour of highly porous Ti-TiB-TiNx in situ composites in simulated physiological solution

Highly porous Ti matrix composites can be a solution for some of the major clinical concerns for the load bearing implants such as low tribocorrosion resistance, stress shielding, and lack of biological anchorage. In order to respond to these needs, highly porous Ti-TiB-TiN_x in-situ composites were synthesized by pressureless sintering using BN as reactant and urea as space holder. Corrosion behaviour was investigated at body temperature, in phosphate buffer saline solution (PBS), by measuring open circuit potential (OCP) and cyclic polarization. Wear behaviour was studied in PBS by reciprocating against a 10 mm diameter alumina ball under 3 N of normal load and 1 Hz of frequency. Results showed that the formation of the in-situ reinforcing phases led to an increase on the hardness and on the wear resistance, as well, neither macro porosity nor the reinforcing phases led to localized corrosion.

Effects of ZIF-8 MOFs on structure and function of blood components

ZIF-8 MOFs, with their large specific surface area and void volume, unique biodegradability and pH sensitivity, and significant loading capacity, have been widely used as carrier materials for bioactive molecules such as drugs, vaccines and genes.

Liquid Phase Separation in Ag-Co-Cr-Fe-Mn-Ni, Co Cr-Cu-Fe-Mn-Ni and Co-Cr-Cu-Fe-Mn-Ni-B High Entropy Alloys for Biomedical Application

The liquid phase separation (LPS) behavior in Co-Cr-based high-entropy alloys (HEAs) is an important target for the development of Co-Cr-based HEAs for metallic biomaterials (BioHEAs). The solidification microstructure in Ag-Co-Cr-Fe-Mn-Ni-Ag, Co-Cr-Cu-Fe-Mn-Ni-Cu, and Co-Cr-Cu-Fe-Mn-Ni-B HEAs, which were designed as the combination of the equiatomic CoCrFeMnNi with Ag, Cu, and the interstitial element of B, was investigated as the fundamental research of LPS in Co-Cr-based HEAs. Ingots of equiatomic AgCoCrFeMnNi, equiatomic CoCrCuFeMnNi, non-equiatomic CoCrCuxFeMnNi (x = 2, 3), and CoCrCuxFeMnNiB0.2 (x = 1, 2, 3) with a small amount of B were fabricated using the arc-melting process. A macroscopic phase-separated structure was observed in the ingots of the equiatomic AgCoCrFeMnNi and CoCrCuxFeMnNiB0.2 (x = 2, 3) HEAs. The addition of a small amount of B enhanced the LPS tendency in the Co-Cr-Fe-Mn-Ni-Cu HEAs. The LPS behavior was discussed through the heat of mixing and computer coupling of phase diagrams and thermochemistry (CALPHAD).

Novel α + β Type Ti-Fe-Cu Alloys Containing Sn with Pertinent Mechanical Properties

Rising demand for bone implants has led to the focus on future alternatives of alloys with better biocompatibility and mechanical strength. Thus, this research is dedicated to the synthesis and investigation of new compositions for low-alloyed Ti-based compounds, which conjoin relatively acceptable mechanical properties and low elastic moduli. In this regard, the structural and mechanical properties of α + β Ti-Fe-Cu-Sn alloys are described in the present paper. The alloys were fabricated by arc-melting and tilt-casting techniques which followed subsequent thermo-mechanical treatment aided by dual-axial forging and rolling procedures. The effect of the concentrations of the alloying elements, and other parameters, such as regimes of rolling and dual-axial forging operation, on the microstructure and mechanical properties were thoroughly investigated. The Ti94Fe1Cu1Sn4 alloy with the most promising mechanical properties was subjected to thermo-mechanical treatment. After a single rolling procedure at 750 °C, the alloy exhibited tensile strength and tensile plasticity of 1300 MPa and 6%, respectively, with an elastic modulus of 70 GPa. Such good tensile mechanical properties are explained by the optimal volume fraction balance between α and β phases and the texture alignment obtained, providing superior alternatives in comparison to pure α- titanium alloys.

The Effects of Various Metallic Surfaces on Cellular and Bacterial Adhesion

The effects of Ti, Nb, Ta, Zr, and Ag on cellular and bacterial adhesion were investigated in this study. Moreover, the relationships between surface compositions, metal ion release behaviors, and biological responses were examined. As a result, MC3T3-E1 cells and S. aureus were able to better attach to Ti and Zr rather than the Nb and Ta specimens. For the Ag specimen, the amount of Ag ions released into Hanks’ solution was the largest among all the specimens. Cellular and bacterial adhesion onto the Ag specimen was inhibited compared with the other specimens, because of Ag ion release. Alternatively, Nb and Ta specimens exhibited specific biological responses. Cellular adhesion on Nb and Ta specimens was similar to that on Ti, while bacterial adhesion on Nb and Ta specimens was inhibited compared with that on Ti. This study proved that Nb and Ta inhibited bacterial adhesion and exhibited no harmful effects on cellular adhesion. In addition, these results indicate that the passive layer on Nb and Ta plays a key role in the inhibition of bacterial adhesion.

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

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

The Electrochemical and Mechanical Behavior of Bulk and Porous Superelastic Ti‒Zr-Based Alloys for Biomedical Applications

Titanium alloys are well recognized as appropriate materials for biomedical implants. These devices are designed to operate in quite aggressive human body media, so it is important to study the corrosion and electrochemical behavior of the novel materials alongside the underlying chemical and structural features. In the present study, the prospective Ti‒Zr-based superelastic alloys (Ti-18Zr-14Nb, Ti-18Zr-15Nb, Ti-18Zr-13Nb-1Ta, atom %) were analyzed in terms of their phase composition, functional mechanical properties, the composition and structure of surface oxide films, and the corresponding corrosion and electrochemical behavior in Hanks’ simulated biological solution. The electrochemical parameters of the Ti-18Zr-14Nb material in bulk and foam states were also compared. The results show a significant difference in the functional performance of the studied materials, with different composition and structure states. In particular, the positive effect of the thermomechanical treatment regime, leading to the formation of a favorable microstructure on the corrosion resistance, has been revealed. In general, the Ti-18Zr-15Nb alloy exhibits the optimum combination of functional characteristics in Hanks’ solution, while the Ti-18Zr-13Nb-1Ta alloy shows the highest resistance to the corrosion environment. The Ti-18Zr-14Nb-based foam material exhibits slightly lower passivation kinetics as compared to its bulk equivalent.

Titanium-Tissue Interface Reaction and Its Control With Surface Treatment

Titanium (Ti) and its alloys are widely used for medical and dental implant devices-artificial joints, bone fixators, spinal fixators, dental implant, etc. -because they show excellent corrosion resistance and good hard-tissue compatibility (bone formation and bone bonding ability). Osseointegration is the first requirement of the interface structure between titanium and bone tissue. This concept of osseointegration was immediately spread to dental-materials researchers worldwide to show the advantages of titanium as an implant material compared with other metals. Since the concept of osseointegration was developed, the cause of osseointegration has been actively investigated. The surface chemical state, adsorption characteristics of protein, and bone tissue formation process have also been evaluated. To accelerate osseointegration, roughened and porous surfaces are effective. HA and TiO2 coatings prepared by plasma spray and an electrochemical technique, as well as alkalinization of the surface, are also effective to improve hard-tissue compatibility. Various immobilization techniques for biofunctional molecules have been developed for bone formation and prevention of platelet and bacteria adhesion. These techniques make it possible to apply Ti to a scaffold of tissue engineering. The elucidation of the mechanism of the excellent biocompatibility of Ti can provide a shorter way to develop optimal surfaces. This review should enhance the understanding of the properties and biocompatibility of Ti and highlight the significance of surface treatment.