In vitro study on Zr-based bulk metallic glasses as potential biomaterials

With pure Ti and pure Zr as controls, the corrosion resistance, ion release behavior, and in vitro biocompatibility of Be-containing Zr₄₁Ti₁₄Cu₁₂Ni₁₀Be₂₃ bulk metallic glass (BMG) (LM1), Zr₄₄Ti₁₁Cu₁₀Ni₁₀Be₂₅ BMG (LM1b), and Be-free Zr₅₇Nb₅Cu₁₅.₄Ni₁₂.₆Al₁₀ BMG (LM106) were investigated in terms of electrochemical measurements in simulated body fluid (SBF) with pH value 7.4 and artificial saliva (AS) with pH value 6.3, and 3-[4,4-dimethylthiazol-2-yl]-2,5-diphenyltetrazolium bromide (MTT) assay using L929 and NIH3T3 cells, aiming to assess the feasibility of Zr-based BMGs as potential biomaterial. It was found that LM1b showed superior corrosion resistance to LM106 and LM1 in both SBF and AS, and comparable with pure Ti and pure Zr. After 7200 s immersion, a two-layer structure oxide film was formed on LM1, LM1b, and pure Zr surfaces, while one-layer structure oxide film was formed on LM106 and pure Ti surfaces. The pitting corrosion potentials of LM1b were much higher than that of LM1, LM106, and pure Zr, resulting in very few ions releasing into the electrolytes. No Be ion could be detected but a little amount of Cu ion was detected for LM106, LM1, and LM1b after immersion in Dulbecco's modified Eagle's medium for 72 h at 37 °C. The indirect cytotoxicity results show that LM106, LM1, and LM1b extracts had no cytotoxicity to L929 and NIH3T3 cells. The direct cytotoxicity results show that cells could adhere well on the Zr-based BMG surface as in pure Ti and Zr. Lower cell proliferation rate of LM106 and LM1 is observed when compared with LM1b, which was found to be caused by Cu ion releasing rather than by Be ion.