Influence of Copper on the Microstructural, Mechanical, and Biological Properties of Commercially Pure Zn-Based Alloys for a Potential Biodegradable Implant

Abstract

Three Zn-based alloys (Zn1Cu, Zn2Cu, and Zn3Cu) were developed by the addition of Cu (1, 2, and 3 wt %) into commercially pure Zn. This report systematically investigates the potential for these newly developed Zn-based alloys as biodegradable materials. Microstructural studies reveal the presence of spherical-shaped nanosized precipitates of ε-CuZn 4 in the Zn1Cu alloy, whereas Zn2Cu and Zn3Cu alloys exhibit the presence of both micron-and nanosized precipitates of ε-CuZn 4 . The mechanical properties such as hardness, tensile and compressive strengths improve significantly with an increase in the amount of Cu in the alloy. The Zn3Cu alloy exhibits the highest yield strength (225 ± 9 MPa) and ultimate tensile strength (330 ± 12 MPa) among all of the alloys, which are ∼2.7 and 2 times higher than those of pure Zn. In vitro degradation behavior is evaluated by the potentiodynamic polarization study and immersion testing in Hank's solution for 20 and 75 days. The corrosion rate after both polarization and immersion testing follows the order of pure Zn < Zn1Cu < Zn3Cu < Zn2Cu. An electrochemical impedance spectroscopy (EIS) study also concludes that Zn2Cu shows the lowest corrosion resistance. The % cell viability values of 3T3 fibroblasts cells after 5 days of culture in a 50% diluted extract of pure Zn, Zn2Cu, and Zn3Cu alloys are 76 ± 0.024, 86.18 ± 0.033, and 92.9 ± 0.026%, respectively, establishing the improved cytocompatibility of the alloys as compared to pure Zn. Furthermore, an antibacterial study also reveals that the Zn3Cu alloy exhibits 80, 67, and 100% increases in the zone of inhibition (ZOI) for Escherichia coli, Bacillus subtilis, and Pseudomonas aeruginosa bacteria, respectively, as compared to that of pure Zn.

Development of Zn-2Cu-xMn/Mg Alloys for Orthopedic Applications: Mechanical Performance to In Vitro Degradation under Different Physiological Environments

“…Table 2 lists the chemical composition of the various physiological fluids described by Liu et al 48 The experimental details were explained in our previous research article. 26 The tests were executed at a scan rate of 1 mV/s over a potential value of −2.5−0.0 V vs open-circuit potential (E OCP ). The corrosion rate and the potentiodynamic polarization parameters of the alloys were assessed according to ASTM-G102-89.…”

“…In our previous research article, it is reported that commercially pure Zn alloying with 2 and 3 wt % of Cu exhibits excellent UTS of 313 and 330 MPa, along with an elongation of 60 and 35%, respectively. 26 The acceptable cell viability of the 3T3 fibroblast cell, good antibacterial behavior, and a suitable degradation rate of ∼0.2 mm/year make the Zn-2Cu alloy a potential candidate for further biomedical research. Tang et al also investigated the effect of Cu (1, 2, 3, and 4 wt %) on the Zn alloys and infer that Zn-4Cu possessed superior mechanical properties, cytocompatibility, and antibacterial effect.…”

Cytotoxicity of Biodegradable Zinc and Its Alloys: A Systematic Review

“…In most studies, a reduction in cell viability of more than 30% was considered a cytotoxic effect, but the threshold for cytotoxicity was at 75% in multiple studies [68,92]. In addition, many of the included studies claimed to have graded the toxicity from quantitative results in extract tests according to ISO standards [32,34,35,45,[52][53][54]86,99].…”

“…These factors include the increase in local pH, change in surface morphology, shedding of the corrosion layer, and surface composition. In addition, cell adhesion and proliferation largely depend on extracellular matrix deposition, which is controlled by the protein adsorption capacity of a matrix surface [86].…”

“…Materials and ProcessingAs shown in Table1, 51 articles involved pure Zn, and 77 investigated Zn-based alloys. The latter mainly consisted of binary and ternary alloys such as Zn-Mg[15,[25][26][27][28]35,43,53,57,70,82], Zn-Cu[23,24,29,37,44,56,60,71,75,80,81,86], Zn-Ag[36,42,66,69], Zn-Mn[41,51,90], and Zn-Li alloys…”