Abstract
The growing interest in Zn based alloys as structural materials for biodegradable implants is mainly attributed to the excellent biocompatibility of Zn and its important role in many physiological reactions. In addition, Zn based implants do not tend to produce hydrogen gas in in vivo conditions and hence do not promote the danger of gas embolism. However, Zn based implants can provoke encapsulation processes that, practically, may isolate the implant from its surrounding media, which limits its capability of performing as an acceptable biodegradable material. To overcome this problem, previous research carried out by the authors has paved the way for the development of Zn-Fe based alloys that have a relatively increased corrosion rate compared to pure Zn. The present study aims to evaluate the effect of 0.3–1.6% Ca on the in vitro behavior of Zn-Fe alloys and thus to further address the encapsulation problem. The in vitro assessment included immersion tests and electrochemical analysis in terms of open circuit potential, potentiodynamic polarization, and impedance spectroscopy in phosphate buffered saline (PBS) solution at 37 °C. The mechanical properties of the examined alloys were evaluated by tension and hardness tests while cytotoxicity properties were examined using indirect cell metabolic activity analysis. The obtained results indicated that Ca additions increased the corrosion rate of Zn-Fe alloys and in parallel increased their strength and hardness. This was mainly attributed to the formation of a Ca-rich phase in the form CaZn13. Cytotoxicity assessment showed that the cells’ metabolic activity on the tested alloys was adequate at over 90%, which was comparable to the cells’ metabolic activity on an inert reference alloy Ti-6Al-4V.
Highlights
Traditional structural materials for metallic implants in orthopedic applications such as bone plates and screws as well as stents for cardiovascular use are produced from stainless steels, Ti based alloys, Cobalt–chromium alloys, and others [1]
The present study aims to evaluate the effect of 0.3–1.6% Ca on in vitro behavior of Zn-Fe alloys in order to further address the encapsulation problem while maintaining adequate mechanical properties
This was followed by a visual examination of the cells was documented by a CoolLED
Summary
Traditional structural materials for metallic implants in orthopedic applications such as bone plates and screws as well as stents for cardiovascular use are produced from stainless steels, Ti based alloys, Cobalt–chromium alloys, and others [1]. These implants have excellent corrosion resistance in in vivo conditions along with superior mechanical properties [2]. Studies related to Mg based alloys [8,9,10,11,12,13,14,15,16,17,18,19] revealed several major problems, including accelerated corrosion rates, premature degradation of mechanical integrity, and the release of hydrogen gas. The accumulation of hydrogen in in vivo conditions can produce gas bubbles that, in extreme
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