Localized Corrosion Mechanisms on Micro-and Nano devices in Biomedical Field

Thus far, both Ti6Al4V and CoCrMo alloys are the most common implant materials in the biomedical field, mainly used in orthopaedic, dental, cardiovascular, and fixing fracture components. The significant capability of these implant materials is due to high corrosion resistance or resistance to metal ion release and specific mechanical properties. However, during implantation in human body media as a complex corrosive environment with various types of ions (phosphate, calcium, chloride, fluoride, etc.), proteins (albumin, fibronectin, globulin, ferritin, etc.), and cells, all these species significantly can influence on implants corrosion behaviour during the lifetime performance. The same story can be described for micro and nanomaterials as innovative and intelligent materials to be used in biological fields for targeted drug delivery, nanosurgery, cancer therapy, and isolation of biological targets. In this research, we employed NiCo and NiCo/Au metallic micropillars and cobalt ferrite (CoFe2O4 (CFO)) and cobalt ferrite@bismuth ferrite (CoFe2O4@BiFeO3 (CFO@BFO)) ceramic nanoparticles. These micro and nano magnetic materials present good chemical stability (especially ceramic nanoparticles), low production cost and can be driven using external magnetic field to the target. However, these tiny smart devices can gradually miss the swimming efficiency, speed, and controllability due to their degradation accelerated by the protein nano-biofilm formation. Protein molecules adsorbed on the surface of biomaterials can control the dynamic physicochemical interactions, on the surfaces of biological components. Depending on the different parts of human body where the biomaterials can be used, different protein species exist with particular biological behaviour which affect the metal ion release such as serumiv albumin, commonly found in blood plasma, or ferritin and apoferritin (ferritin without iron core), presented in spleen, liver, and inflammatory macrophages. To investigate the protein adsorption, morphology, and its influence on degradation mechanisms in the surgical implants or large-scale materials (CoCrMo and Ti6Al4V alloys), bovine serum albumin (BSA) protein with various concentrations was added in phosphatebuffered saline (PBS) solution. In addition, in micro-scale materials or NiCo and NiCo/Au micropillars, BSA protein was selected to monitor the metal ion releasing process in PBS media and its effect on the degradation mechanism for a long-term period. In the nano-scale materials or CFO and CFO@BFO nanoparticles, which due to their chemical nature are stable in PBS environment containing albumin protein, apoferritin was used to monitor the protein molecule role on both metal ion releasing and up-taking processes of nanoparticles in PBS media during immersion for a long-term period. A multi-technique characterization based on electrochemical measurements, microscopy, and spectroscopy analyses was used to visualize the electrochemical interactions at electrolyte/protein/solid interfaces, the protein adsorption morphology and its impact on chemical stability of passive film (CoCrMo, Ti6Al4V, NiCo micropillar) and oxide surface (ceramic nanoparticles). We believe that the combination of findings in our research can provide new insight into the protein adsorption and its effect on the metal ion releasing process of all metallic and ceramic biomaterials during the performance in the human body as a complex biological environment.