 Johnson I*, Liu H. A Study on Factors Affecting the Degradation of Magnesium and A Magnesium-Yttrium Alloy for Biomedical Applications. PLOS ONE. 8(6): e65603, 2013. Abstract
- Controlling degradation of magnesium or its alloys in physiological
saline solutions is essential for their potential applications in
clinically viable implants. Rapid degradation of magnesium-based
materials reduces the mechanical properties of implants prematurely and
severely increases alkalinity of the local environment. Therefore, the
objective of this study is to investigate the effects of three
interactive factors on magnesium degradation, specifically, the addition
of yttrium to form a magnesium-yttrium alloy versus pure magnesium, the
metallic versus oxide surfaces, and the presence versus absence of
physiological salt ions in the immersion solution. In the immersion
solution of phosphate buffered saline (PBS), the magnesium-yttrium alloy
with metallic surface degraded the slowest, followed by pure magnesium
with metallic or oxide surfaces, and the magnesium-yttrium alloy with
oxide surface degraded the fastest. However, in deionized (DI) water,
the degradation rate showed a different trend. Specifically, pure
magnesium with metallic or oxide surfaces degraded the slowest, followed
by the magnesium-yttrium alloy with oxide surface, and the
magnesium-yttrium alloy with metallic surface degraded the fastest.
Interestingly, only magnesium-yttrium alloy with metallic surface
degraded slower in PBS than in DI water, while all the other samples
degraded faster in PBS than in DI water. Clearly, the results showed
that the alloy composition, presence or absence of surface oxide layer,
and presence or absence of physiological salt ions in the immersion
solution all influenced the degradation rate and mode. Moreover, these
three factors showed statistically significant interactions. This study
revealed the complex interrelationships among these factors and their
respective contributions to degradation for the first time. The results
of this study not only improved our understanding of magnesium
degradation in physiological environment, but also presented the key
factors to consider in order to satisfy the degradation requirements for
next-generation biodegradable implants and devices. |
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