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

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

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

Titanium alloys: in vitro biological analyzes on biofilm formation, biocompatibility, cell differentiation to induce bone formation, and immunological response

Biological effects of titanium (Ti) alloys were analyzed on biofilms of Candida albicans, Enterococcus faecalis, Pseudomonas aeruginosa, Staphylococcus aureus, Streptococcus mutans, and Streptococcus sanguinis, as well as on osteoblast-like cells (MG63) and murine macrophages (RAW 264.7). Standard samples composed of aluminum and vanadium (Ti-6Al-4V), and sample containing niobium (Ti-35Nb) and zirconium (Ti-13Nb-13Zr) were analyzed. Monomicrobial biofilms were formed on the Ti alloys. MG63 cells were grown with the alloys and the biocompatibility (MTT), total protein (TP) level, alkaline phosphatase (ALP) activity, and mineralization nodules (MN) formation were verified. Levels of interleukins (IL-1β and IL-17), tumor necrosis factor alpha (TNF-α), and oxide nitric (NO) were checked, from RAW 264.7 cells supernatants. Data were statically analyzed by one-way analysis of variance (ANOVA) and Tukey's test, or T-test (P ≤ 0.05). Concerning the biofilm formation, Ti-13Nb-13Zr alloy showed the best inhibitory effect on E. faecalis, P. aeruginosa, and S. aureus. And, it also acted similarly to the Ti-6Al-4V alloy on C. albicans and Streptococcus spp. Both alloys were biocompatible and similar to the Ti-6Al-4V alloy. Additionally, Ti-13Nb-13Zr alloy was more effective for cell differentiation, as observed in the assays of ALP and MN. Regarding the stimulation for release of IL-1β and TNF-α, Ti-35Nb and Ti-13Nb-13Zr alloys inhibited similarly the synthesis of these molecules. However, both alloys stimulated the production of IL-17. Additionally, all Ti alloys showed the same effect for NO generation. Thus, Ti-13Nb-13Zr alloy was the most effective for inhibition of biofilm formation, cell differentiation, and stimulation for release of immune mediators.

Graphene nanoplatelets-sericin surface-modified Gum alloy for improved biological response

In this study a “Gum Metal” titanium-based alloy, Ti-31.7Nb-6.21Zr-1.4Fe-0.16O, was synthesized by melting and characterized in order to evaluate its potential for biomedical applications. The results showed that the newly developed alloy presents a very high strength, high plasticity and a low Young's modulus relative to titanium alloys currently used in medicine. For further bone implant applications, the newly synthesized alloy was surface modified with graphene nanoplatelets (GNP), sericin (SS) and graphene nanoplatelets/sericine (GNP–SS) composite films via Matrix Assisted Pulsed Laser Evaporation (MAPLE) technique. The characterization of each specimen was monitored by scanning electron microscopy (SEM), atomic force microscopy (AFM), contact angle (CA) measurements, and Fourier Transform Infrared Spectroscopy (FTIR). The materials' surface analyses suggested the successful coating of GNP, SS and GNP–SS onto the alloy surface. Additionally, the activities of pre-osteoblasts such as cell adhesion, cytoskeleton organization, cell proliferation and differentiation potentials exhibited on these substrates were investigated. Results showed that the GNP–SS-coated substrate significantly enhanced the growth and osteogenic differentiation of MC3T3-E1 cells when compared to bare and GNP-coated alloy. Collectively, the results show that GNP–SS surface-modified Gum alloy can modulate the bioactivity of the pre-osteoblasts holding promise for improved biological response in vivo.

GNP–SS functionalized Gum alloy exhibits superior bioactivity in inducing in vitro osteogenesis.