In Vivo Simulation of Magnesium Degradability Using a New Fluid Dynamic Bench Testing Approach

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.

Biocompatibility and Immune Response of a Newly Developed Volume-Stable Magnesium-Based Barrier Membrane in Combination with a PVD Coating for Guided Bone Regeneration (GBR)

“…In vitro, both membrane entities showed poor cytocompatibility with signs of massive gas bubble formation. In comparison, MG-Co showed inferior values than MG. Gas bubbles can be interpreted as a sign of degradation, which has been shown in previous publications [ 30 , 31 ]. However, the passivation seems to be an even triggering factor for degradation and the PVD coating was visible as black discoloration in the live–dead staining.…”

“…In the cytotoxicity tests, values < 130% of the medium control in the cytotoxicity assay (LDH) and values > 70% of the medium control in the proliferation and cell differentiation assays (XTT, BrdU) are within the nontoxic range according to ISO 10993-5:2009 ( Figure 1 ) [ 5 , 29 , 30 , 31 ]. Thereby, both treated and untreated magnesium membranes showed values outside these limits in all assays.…”

“…Cytocompatibility analysis was conducted in accordance with the ISO 10993-5/-12 as described in our previous publications [ 5 , 29 , 30 , 31 ]. Therefore, the process is briefly summarized:…”

Comparative Assessment of In Vitro and In Vivo Biodegradation of Mg-1Ca Magnesium Alloys for Orthopedic Applications

“…The pH in both corrosion environments reached high values, raising the hypothesis of in vivo cytotoxicity phenomena [ 36 ]. The hydrogen release rate is higher than the human body absorption rate, predisposing to the formation of gas bubbles.…”

Bioactive Glass Coated Zirconia for Dental Implants: a review

“…Their biological inertness and electrical passivation have made ceramics a promising material in the medical equipment and medicine. In comparison with metallic implants, zirconia-based ceramics show minimum ion release and are biologically inert [14][15][16][17][18][19][20][21][22][23][24][25][26][27][28][29][30][31][32]. Modern Ti implant technologies are being introduced due to possible combination of immunologic and aesthetic aspects of Ti and Ti alloys.…”