Cytotoxicity of Zr-based bulk metallic glasses

Recently we developed a family of Ni-free Zr-based bulk metallic glasses in the Zr–Cu–Fe–Al system. X-ray diffraction and differential thermal analysis measurements demonstrate its good glass-forming ability, and amorphous rods of up to 13 mm in diameter can be produced for the alloy Zr₅₈Cu₂₂Fe₈Al₁₂. This new glassy system is potentially very interesting for biomedical applications. Thus we have investigated the effect of surface modification (treatment with nitric acid and oxygen plasma) on the alloy's cytotoxicity and compared it with the results for a Ni-bearing Zr-based bulk metallic glass. The surfaces were analyzed by X-ray photoelectron spectroscopy, and cytotoxicity was tested by measuring the viability and metabolic activity of mouse fibroblasts. Our results show that the surfaces of the as-cast glasses consist almost exclusively of zirconium oxide, which yields good biocompatibility. With nitric acid treatment this oxide layer can be stabilized further, to the extent that the cytotoxicity becomes as good as that of the non-toxic negative control (polystyrene).