Electrochemical nanostructuring of surfaces of bulk metallic glasses on Ti-Cu basis for improvement of their biocompatibility

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Owing to their high mechanical biofunctionality bulk metallic glasses (BMG) on Ti-Cu base are considered as prospective new materials for bone implants in the fields of dentistry and trauma surgery. However, in comparison to materials in current clinical use their biocompatibility is still insufficient. A critical aspect is their high Cu content, which can cause local corrosion phenomena and in consequence, the release of toxic species and mechanical material failure. Moreover, for those BMGs there are so far no reliable concepts for the generation of bioactive surface states which are mandatory for permanent implants. In the applied project a method for an electrochemical nanostructuring of surfaces of multicomponent Ti-Cu-based BMGs will be developed with the objective of effectively improving the biocompatibility and corrosion stability. The method is targeted on significantly reducing the concentration of alloying elements which are necessary for obtaining high glass-forming ability but which are critical with respect to biocompatibility, from near-surface regions. At the same time nanoporous, predominantly oxidic surface structures will be generated in order to improve the corrosion resistance and to stimulate the activity of bone cells. The mechanical performance of the BMGs must not be significantly affected. In the project two promising bulk glass-forming Ti-Cu alloys are subject of investigation for which the casting processes are already established at the IFW Dresden. For the nanostructuring, anodic treatments of glassy samples in halogenide-free acid solutions are primarily employed. The effects of treatment parameters on the developing surface states are fundamentally investigated and the underlying surface reaction mechanisms are described. A key aspect is the analysis of the impact of those surface states on the corrosion behaviour of the BMGs in synthetic physiological solutions. In particular the pitting corrosion susceptibility is to be reduced by the generation of tailored oxidic states. By means of cell biological studies the effect of selected surface states on the behaviour of human mesenchymal stroma cells (hBMSC) and of periodontal ligament fibroblasts will be fundamentally evaluated. Exemplarily, for one selected BMG the impact of surface nanostructuring on the mechanical properties under compression and tensile load will be assessed. In result of these studies, fundamental relations between structural and chemical particularities of the Ti-Cu-based BMGs, derivable routes for electrochemical surface nanostructuring and resulting corrosive, mechanical and cell biological properties will be described.