An ideal bioresorbable foam for bone replacement should have porous structure similar to the architecture of natural bones, suitable mechanical properties, and resorb in the body entirely after a proper healing time. Magnesium satisfies these conditions in combining both biocompatible and bioresorbable properties simultaneously while accelerating bone regeneration . Its natural degradation property can avoid the need for a second surgical procedure to remove the implant. However, since magnesium resorbs too fast it is crucial to retard the surface corrosion mostly in the early stage of bone growth to avoid hydrogen release and enhance tissue integration .
In the present work, AZ31 foams with 65% porosity and 420 µm pore size, prepared by infiltration casting, were modified by Directed Plasma Nanosynthesis (DPNS) at different low energy irradiation values. This surface modification varied the amount of Al content on the near surface and created dynamic interactions between the foam surface and the environment when exposed to simulated body fluid. Moreover, a specific combination of DPNS parameters, 400 eV ion energy and 1E18 fluence, led to the growth of a bioactive and corrosion protective hydroxyapatite interface while maintaining bulk architected foam metal properties.
The corrosion process and bioactivity of the obtained surfaces were tested in vitro. Then, the micro and nanostructural properties, the developed phases, and their morphology were evaluated by SEM/EDS, XPS, and XRD. The in vitro biocompatibility tests were performed using bone marrow-derived mesenchymal stem cells. Cell viability was evaluated by Alamar blue after 1, 4, and 7 days. Cell morphology was evaluated by SEM and immunostaining using DAPI and Texas-Red-X Phalloidin. As a result, the interaction between the irradiation parameters and the immersion medium tune the surface properties and therefore, the corrosion resistance and bioactive properties. Hence, DPNS can be used to tailor desired conversion surfaces and cellular responses.