Biodegradation Study of Magnesium-based Implant Materials under Physiological Conditions
Biodegradable magnesium and its alloys are new-generation materials for orthopaedic implants. In vitro setups utilising physiological conditions are promising for material/degradation analysis prior to animal experiments. The work of this study is divided into two parts. In part 1, the influence of important blood plasma salts on pure magnesium degradation and its product composition was elucidated first in Hank’s Balanced Salt solution without calcium or magnesium (HBSS) and then in complex cell culture media; Dulbecco’s Modified Eagle’s Medium (DMEM) and Roswell Park Memorial Institute medium (RPMI-1640). In part 2, the direct influence of osteoblast cells on the degradation of pure magnesium and two alloys, Mg-2Ag and Mg-10Gd was studied. The degradation layer was analysed with Electron-Induced X-ray Emission (EIXE) spectroscopy and Fourier Transform Infrared Reflection micro-spectroscopy (FTIR). The degradation interface (directly beneath the cells) was analysed with a new approach that uses a scanning electron microscope equipped with energy-dispersive X-ray and a focused ion beam. The results highlight the importance of bicarbonate as a blood-buffering salt on the formation of magnesium carbonate as main degradation product. Deposition of calcium phosphate precipitations reduced the degradation. Results also indicate the role of osteoblasts in altering the chemical composition by forcing apatite precipitations.
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