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Analyzing gas cavity formation at implant sites

H2 measurements in mice

Magnesium materials show promise for the development of biodegradable implants. The material is light in weight, generally non-toxic and its physical and mechanical properties resemble bone. However, the material suffers from the formation of gas cavities at implantation sites.

This phenomenon has been known for decades, but the exact gas composition has been unknown. Magnesium implants corrode rapidly in aqueous environments by oxidation of Mg to Mg2+ as water is reduced to H2 and OH-. Kuhlmann et al (2012) used the Unisense H2 microsensor to determine H2 concentration in the gas cavities and to monitor how quickly H2 exchanged with the environment.

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In situ H2 measurements

Magnesium alloy implants were placed in subcutaneous pockets in mice. During measurements the anesthetized mouse was positioned on a swiveling table. The Unisense H2 microsensor was connected to the Microsensor Multimeter and positioned in a micromanipulator to measure H2 concentration on the skin on top of the gas cavities. H2 concentration was measured 0, 2, 5 and 10 days post-surgery.

Based on microsensor results Kuhlmann et al showed that H2 could be detected on the skin on top of the gas cavities as well as in the cavities. However, the H2 concentration was very low, which led the research team to the conclusion that H2 produced during implant corrosion was quickly exchanged with the environment. Due to the fast response and high sensitivity of the Unisense H2 microsensor, it was possible to detect variations in H2 concentration in and at the gas cavities.

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Fast escape of hydrogen from gas cavities around corroding magnesium implants
Kuhlmann, Julia et al. (2013), Acta Biomaterialia, vol. 9, 8714-8721
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