Characterization of the Ti-Sn-Nb alloy with Mg and its biotechnological potential in bone healing

Author(s)

Mariana Correa Rossi

• Document type: Doctoral Thesis
• Press: Botucatu. 2021-05-07.
• Institution: Universidade Estadual Paulista (Unesp). Faculdade de Medicina Veterinária e Zootecnia. Botucatu
• Defense date: 2021-03-01
• Advisor: Ana Liz Garcia Alves; Margarida Juri Saeki

Abstract

Most of the commercialized metallic materials have certain inconveniences, such as toxicity and discrepant elastic modulus compared to bone tissue. These characteristics promote a decrease in the longevity of them when implanted and can lead to respiratory and neurological disorders depending on the components present. In this way, materials that use elements such as Nb (stabilizer β) and Sn (neutral element), in titanium alloys are studied in order to achieve more appropriate characteristics, by increasing the β phase and decreasing the elastic modulus. The objective was to obtain the Ti-34Nb-6Sn alloy, by powder metallurgy, and its physical, chemical, mechanical and biological characterizations. In the process, a spacer, Mg, was added in order to impart porosity to the alloy. Sintering was carried out at 700ºC, 800ºC and 900ºC. The physical characterization was made by X-ray diffraction (XRD), scanning electron microscopy (SEM), semi-quantitative compositional analysis by X-ray dispersive energy (EDS) and analysis of wettability by dynamic contact angle measurements. The mechanical characteristics such as the elastic modulus, compressive strength and Vickers hardness were studied. The corrosion susceptibility was studied by the electrochemical method in HANK and Fusayama solution that simulates the body fluid and saliva. In biological assays, bone marrow-derived mesenchymal stem cells (BMMSCs) from horses were used. Cytotoxicity analyzes were performed with the specimens, as well as analyzes of the potential for cell migration and differentiation. In the presence of Nb and Sn, the material becomes richer in the β phase as the sintering temperature increases. With Mg, greater resistance to α → β allotropic transformation was observed, obtaining materials with lower β phase content than that without Mg. The porosity was higher for the materials with Mg, as well as the surface wettability. The elastic modulus and hardness were lower for the materials with Mg and the lower the sintering temperature and closer to bone tissue. The mechanical strength was higher for the alloy without Mg. The alloy sintered with Mg at 800ºC was more resistant to corrosion compared to the alloy without Mg. Both materials showed good biocompatibility when in contact with BMMSCs, with the ability to adhere to the surface and inside the pores. In addition, BMMSCs showed a marked osteogenic differentiation process when fed with the conditioned medium with the alloy, possibly due to the release of Mg in the culture medium. After 24 hours, through the cell migration test, cells that had contact with the alloy with Mg showed a significant directional migration process compared to the control group. (AU)

• FAPESP's process: 17/13876-2 - Characterization of Ti-Nb-Sn alloy with Mg and its Biotechnological Potential Bone Fracture Repair.
• Grantee: Mariana Correa Rossi
• Support Opportunities: Scholarships in Brazil - Doctorate