Design and development of novel antibacterial Ti-Ni-Cu shape memory alloys for biomedical application

Abstract

In the case of medical implants, foreign materials are preferential sites for bacterial adhesion and microbial contamination, which can lead to the development of prosthetic infections. Commercially biomedical TiNi shape memory alloys are the most commonly used materials for permanent implants in contact with bone and dental, and the prevention of infections of TiNi biomedical shape memory alloys in clinical cases is therefore a crucial challenge for orthopaedic and dental surgeons. In the present study, copper has been chosen as the alloying element for design and development novel ternary biomedical Ti‒Ni‒Cu shape memory alloys with antibacterial properties. The effects of copper alloying element on the microstructure, mechanical properties, corrosion behaviors, cytocompatibility and antibacterial properties of biomedical Ti‒Ni‒Cu shape memory alloys have been systematically investigated. The results demonstrated that Ti‒Ni‒Cu alloys have good mechanical properties, and remain the excellent shape memory effects after adding copper alloying element. The corrosion behaviors of Ti‒Ni‒Cu alloys are better than the commercial biomedical Ti‒50.8Ni alloys. The Ti‒Ni‒Cu alloys exhibit excellent antibacterial properties while maintaining the good cytocompatibility, which would further guarantee the potential application of Ti‒Ni‒Cu alloys as future biomedical implants and devices without inducing bacterial infections.

Figure 1

Optical micrographs ((a) Ti‒50.8Ni, (b) Ti‒49.8Ni‒1Cu, (c) Ti‒46.8Ni‒4Cu, (d) Ti‒43.8Ni‒7Cu and (e) Ti‒40.8Ni‒10Cu) and XRD patterns (f) of Ti‒50.8Ni and Ti‒Ni‒Cu alloys.

Figure 2

DSC curves of Ti‒50.8Ni and Ti‒Ni‒Cu alloys: (a) Ti‒50.8Ni, (b) Ti‒49.8Ni‒1Cu, (c) Ti‒46.8Ni‒4Cu, (d) Ti‒43.8Ni‒7Cu and (e) Ti‒40.8Ni‒10Cu.

Figure 3

Stress-strain curves in the loading and unloading cyclic tensile tests ((a) Ti‒50.8Ni, (b) Ti‒49.8Ni‒1Cu, (c) Ti‒46.8Ni‒4Cu, (d) Ti‒43.8Ni‒7Cu and (e) Ti‒40.8Ni‒10Cu) and representative tensile stress-strain curves of Ti‒50.8Ni and Ti‒Ni‒Cu alloys at room temperature.

Figure 4

OCP curves (a,b) and potentiodynamic polarization curves (c,d) of pure Ti, pure Ni, pure Cu, Ti‒50.8Ni, and Ti‒Ni‒Cu alloys tested in AS (a,c) and ASFL (b,d) solutions.

Figure 5

Cell viability of (a) L929 and (b) MG63 cells cultured in extracts of pure Ti, pure Ni, pure Cu, Ti‒50.8Ni, and Ti‒Ni‒Cu alloys for 1, 2 and 4 days.

Figure 6

Representative photos of S. aureus (A) and E. coli (B) after 24 h incubation: (a) blank control, (b) pure Ti, (c) pure Ni, (d) pure Cu, (e) Ti‒50.8Ni, (f) Ti‒49.8Ni‒1Cu, (g) Ti‒46.8Ni‒4Cu, (h) Ti‒43.8Ni‒7Cu and (i) Ti‒40.8Ni‒10Cu.

Figure 7

SEM images of adherent S. aureus (A) E. coli (B) after 24 h incubation with (a) pure Ti, (b) pure Ni, (c) pure Cu, (d) Ti‒50.8Ni, (e) Ti‒49.8Ni‒1Cu, (f) Ti‒46.8Ni‒4Cu, (g) Ti‒43.8Ni‒7Cu and (h) Ti‒40.8Ni‒10Cu.

Figure 8

Statistical results of planktoni and adherent S. aureus (A) and E. coli (B) after (a) 4 h and (b) 24 h incubation. (* indicates the statistically significant difference (p < 0.05) when compared to pure Ti.) and (C) schematic diagram for antibacterial mechanism of TiNiCu alloys.