Yen-Hao Chang

Titanium alloys are widely employed for the fabrication of biomedical devices. In this study, we designed and developed a Ti-5Al-2.5Cu alloy, which exhibited antibacterial properties. Microstructure and elemental analyses were performed using X-ray diffraction (XRD), scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDS), and transmission electron microscopy (TEM). We evaluated the alloy’s antibacterial properties using Escherichia coli in the plate-count method. The cytotoxicity was examined using the MG-63 cell response by 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyl tetrazolium bromide (MTT) and lactate dehydrogenase (LDH) assays. Microstructural analysis revealed that Ti-5Al-2.5Cu exhibited an equiaxed α’ martensite structure after short-term annealing. The heterogeneous and homogeneous α → α + Ti₂Cu phase transitions occurred at ~840 and 920 °C, respectively. The antibacterial property for Ti-5Al-2.5Cu was varied by volume fraction in the Ti₂Cu and Cu-rich phase, which was obtained using different heat treatments. The high volume fraction of the Ti₂Cu and Cu-rich phase was observed after long-term annealing at 720–840 °C and thus exhibited a higher antibacterial rate. The relationship between phase distribution and the antibacterial property could be satisfied by a positive linear regression equation. Cytotoxicity results showed that heat treatments at different temperatures for Ti-5Al-2.5Cu alloys had no effect on cell viability. The optimal heat treatment for Ti-5Al-2.5Cu alloy was annealing at 760 °C for 24 h. After, the alloy exhibited both promising antibacterial performance and good cytocompatibility.

Currently, the development of biomaterials has focused on having a low Young’s modulus, biocompatibility, corrosion resistance, and antibacterial properties. Ti–Nb alloys have higher research value due to their excellent corrosion resistance and low Young’s modulus. In recent years, the antibacterial properties of materials have been enhanced by the addition of Ag and Cu. Therefore, the corrosion resistance and antibacterial properties of the Ti–12Nb–1Ag alloy formulated in the current study were investigated and compared to those of commonly used Ti alloys, G2 pure Ti (ASTM B348 CP Grade 2), and Ti–6Al–4V, via electrochemical and E. coli antibacterial tests. Meanwhile, we also carried out a microstructural analysis to investigate the composition of the alloy. The results were as follows: (1) The electrochemical test demonstrated that Ti–12Nb–1Ag had a higher corrosion resistance than Ti–6Al–4V, which is similar to the properties of pure Ti. (2) The E. coli antibacterial test demonstrated that the sterilization rate of Ti–12Nb–1Ag was higher than that of the Ti–6Al–4V alloy and pure Ti. (3) The microstructural analysis revealed that Ti–12Nb–1Ag had an acicular martensite structure, with nano-Ag precipitates observed. Based on the results of the E. coli antibacterial test and the principles of sterilization of nano-precipitates and Ag, we inferred that the nano-Ag precipitates of Ti–12Nb–1Ag enhanced the antibacterial properties of the newly developed biomaterial, which is, namely, the Ti–12Nb–1Ag alloy.