Toxicity assessment and selective leaching characteristics of Cu-Al-Ni shape memory alloys in biomaterials applications

Cu-Al-Ni shape memory alloys (SMAs) possess two-way shape memory effects, superelasticity, and damping capacity. Nonetheless, Cu-Al-Ni SMAs remain promising candidates for use in biomedical applications, as they are more economical and machinable than other SMAs. Ensuring the biocompatibility of Cu-Al-Ni SMAs is crucial to their development for biomedical applications. Therefore, this study aimed to assess the toxicity of Cu-Al-Ni SMAs using a Probit dose–response model and augmented simplex design.

In this study, the effects of Cu²⁺, Al³⁺ and Ni²⁺ metal ions on bacteria (Escherichia coli DH5α) using Probit dose–response analysis and augmented simplex design to assess the actual toxicity of the Cu-Al-Ni SMAs.

Extraction and repetition of Escherichia coli DH5α solutions with high Cu²⁺ ion concentrations and 30-hour incubation demonstrated that Escherichia coli DH5α was able to alter its growth mechanisms in response to toxins. Metal ions leached from Cu-Al-Ni SMAs appeared in a multitude of compositions with varying degrees of toxicity, and those appearing close to a saddle region identified in the contour plot of the augmented simplex model were identified as candidates for elevated toxicity levels. When the Cu-13.5Al-4Ni SMA plate was immersed in Ringer’s solution, the selective leaching rate of Ni²⁺ ions far exceeded that of Cu²⁺ and Al³⁺. The number of Cu²⁺, Al³⁺ and Ni²⁺ ions leached from Cu-Al-Ni SMAs increased with immersion time; however, at higher ratios, toxicity interactions among the metal ions had the effect of gradually reducing overall toxicity levels with regard to Escherichia coli DH5α.

The quantities of Cu²⁺, Al³⁺ and Ni²⁺ ions leached from the Cu-13.5Al-4Ni SMA plate increased with immersion time, the toxicity interactions associated with these compositions reduced the actual toxicity to Escherichia coli DH5α.