2019 · Jung — In Vivo Simulation of Magnesium Degradability Using a New Fluid Dynamic Bench Testing Approach
Super-Abstract
A new dynamic test bench was constructed to measure hydrogen gas (H₂) release during the degradation of magnesium-based implants — using H₂ evolution as a proxy for degradation rate under physiological conditions. Plasma-electrolytically oxidized (PEO) magnesium alloys showed significantly reduced and more uniform degradation compared to untreated WE43 alloy. This is an in-vitro biomaterials engineering study; the H₂ measured here is a degradation by-product, not a therapeutic intervention. (International Journal of Molecular Sciences, 2019.)
Commentary
This paper addresses a practical engineering challenge in orthopaedic biomaterials: biodegradable magnesium implants degrade in vivo and release hydrogen gas as a by-product — which can cause adverse tissue effects if release is too rapid. Jung et al. build a dynamic bioreactor bench that quantifies H₂ evolution under flow and temperature conditions mimicking the body. The core finding is that PEO surface treatment dramatically stabilises degradation rate and reduces H₂ gas production. The study uses H₂ measurement as a diagnostic tool for implant safety rather than exploring any therapeutic property of molecular hydrogen. It is relevant to the H₂ database as a safety-context reference (i.e., what H₂ concentrations arise near degrading Mg implants), but is not evidence for H₂ as a health intervention.
Key quotes
- „a dynamic test bench with several single bioreactor cells was constructed to measure the volume of hydrogen gas which evolves during magnesium degradation to indicate the degradation rate in vivo“ — H₂ evolution used as a real-time marker of degradation, not as therapy
- „The non-ceramized specimens showed the highest degradation rates and vast standard deviations. In contrast, the two PEO samples demonstrated reduced degradation rates with diminished standard deviation.“ — PEO surface treatment improves predictability and slows Mg breakdown
- „PEO treatment of magnesium is a promising method to adjust magnesium degradation“ — conclusion: PEO as implant surface engineering strategy
Our assessment
This is an in-vitro biomaterials engineering study — it does not investigate molecular hydrogen as a therapeutic agent. H₂ gas here is an unwanted degradation by-product that must be minimised for implant safety. The study is methodologically solid, introducing a validated bench model that correlates well with in-vivo data. Its relevance to H₂ medicine is indirect: it helps understand how much H₂ can be released from Mg-based medical devices. No health claims for H₂ can be derived from this paper.
Study design
- Type: in-vitro / bench-top engineering study · Model: dynamic bioreactor cells with physiological flow (37 °C, body-fluid-like medium) · H₂ intervention: none — H₂ measured as degradation by-product
- Materials tested: Mg alloy WE43 (untreated), WE43-PEO variant 1, WE43-PEO variant 2
- Result: PEO-treated samples showed reduced and more uniform H₂ evolution and degradation rates; untreated WE43 showed highest and most variable degradation; PDP and SEM confirmed corrosion resistance improvements; PEO samples exhibited satisfactory cytocompatibility
Abstract
The degradation rate of magnesium (Mg) alloys is a key parameter to develop Mg-based biomaterials and ensure in vivo-mechanical stability as well as to minimize hydrogen gas production, which otherwise can lead to adverse effects in clinical applications. However, in vitro and in vivo results of the same material often differ largely. In the present study, a dynamic test bench with several single bioreactor cells was constructed to measure the volume of hydrogen gas which evolves during magnesium degradation to indicate the degradation rate in vivo. Degradation medium comparable with human blood plasma was used to simulate body fluids. The media was pumped through the different bioreactor cells under a constant flow rate and 37 °C to simulate physiological conditions. A total of three different Mg groups were successively tested: Mg WE43, and two different WE43 plasma electrolytically oxidized (PEO) variants. The results were compared with other methods to detect magnesium degradation (pH, potentiodynamic polarization (PDP), cytocompatibility, SEM (scanning electron microscopy)). The non-ceramized specimens showed the highest degradation rates and vast standard deviations. In contrast, the two PEO samples demonstrated reduced degradation rates with diminished standard deviation. The pH values showed above-average constant levels between 7.4-7.7, likely due to the constant exchange of the fluids. SEM revealed severe cracks on the surface of WE43 after degradation, whereas the ceramized surfaces showed significantly decreased signs of corrosion. PDP results confirmed the improved corrosion resistance of both PEO samples. While WE43 showed slight toxicity in vitro, satisfactory cytocompatibility was achieved for the PEO test samples. In summary, the dynamic test bench constructed in this study enables reliable and simple measurement of Mg degradation to simulate the in vivo environment. Furthermore, PEO treatment of magnesium is a promising method to adjust magnesium degradation.
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