The effect of osteoblasts on the surface oxidation processes of biodegradable Mg and Mg-Ag alloys studied by synchrotron IR microspectroscopy

High-resolution analytical methods, including synchrotron infrared microspectroscopy combined with wavelength-dispersive X-ray emission spectroscopy were applied to study the structure and chemical composition of the oxidized layer of pure and Ag-alloyed Mg exposed to cell culture media without and with osteoblasts. Comparative analysis has been done on pure Mg immersed in two different cell culture media: Dulbecco's Modified Eagle's Medium (DMEM) and Roswell Park Memorial Institute medium (RPMI), whereas Mg-xAg binary alloys (x = 2, 4, 6, 8 wt%) were studied after immersion in DMEM. It is shown that the physicochemical formation of degradation products as well as the activity of the biological component is influenced by the addition of silver. It could be demonstrated that the presence of Ag in the Mg alloy enhances the chemical reaction between Mg and C to form amorphous and/or crystalline MgCO3 on account of CaCO3. As a consequence, the further available P and Ca react easily to form Mg-poor amorphous calcium phosphate phases. Osteoblasts actively adjusted these phases towards hydroxyapatite-like phases.