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The efforts to develop structural materials for biodegradable metal implants have lately shifted their focus from Magnesium and Iron base alloys towards Zinc. This was mainly due to the accelerated corrosion rate of Mg that is accompanied by hydrogen gas evolution, formation of voluminous iron oxide products with reduced degradation rate in the case of Iron implants and the crucial role of Zn in many physiological processes. However the mechanical properties and degradation capabilities of pure zinc in physiological environment are limited and do not comply with the requirements of biodegradable implants. The present study aims at evaluating the effect of 4%Fe on the in-vitro and in-vivo behavior of pure Zinc. This was carried out in order to address the inherent disadvantages of pure zinc in terms of mechanical properties and biodegradability. The results obtained clearly indicate that the biocompatibility and mechanical properties of the new material system was in accord with the prospective requirements of biodegradable implants. However the corrosion degradation of the new alloy in in-vivo conditions was quite similar to that of pure zinc in spite of the significant micro-galvanic effect created by Delta phase Zn 11 Fe.

The disadvantage of current biodegradable metals such as Mg and Fe is the release of hydrogen gas in vivo that can cause gas embolism and the production of voluminous iron oxide that can cause inflammation, respectively. Such considerations have turned focus towards Zn as an alternative. This is based on the fact that Zn plays a crucial role in many physiological processes, as well as potentially being biocompatible and capable of with biodegradation. As such, the purpose of the present study was to evaluate the in vivo performance of pure Zinc and Zn-2%Fe implants. The use of iron as an alloying element was aimed at accelerating the corrosion rate of pure zinc by a micro-galvanic effect so as to maintain the post-implantation biodegradation characteristics of the implant. In vivo assessment was carried out using cylindrical disks implanted in the back midline of 16 male Wistar rats for up to 24 weeks. Post-implantation evaluation included monitoring the well-being of rats, weekly examination of hematological parameters: serum Zn levels, red and white blood cell counts and hemoglobin levels, X-ray radiography, histological analysis and corrosion rate assessment. The results obtained in terms of well-being, hematological tests and histological analysis of the rats indicate that the in vivo behavior of pure Zn and Zn-2%Fe implants was adequate and in line with the results obtained by the control group containing inert Ti-6Al-4V alloy implants. The corrosion rate of Zn-2%Fe alloy in in vivo conditions was relatively increased compared to pure Zn due to micro-galvanic corrosion.