Effects of proteins on magnesium degradation - static vs. dynamic conditions

The interaction between organic molecules and biomaterial surfaces determines the fate of biomaterials during their service life, which is also the research hotspots in the field of biomaterials. To understand the mechanism of protein interaction with magnesium (Mg) degradation, alloying elements, immersion time, protein concentration and surface conditions have been previously considered for the effect of proteins on Mg degradation. However, fluid flow, as one of the critical factors, drew little attention in this case. In the present study, the effect of bovine serum albumin (BSA) and fetal bovine serum (FBS) on Mg degradation was compared under static and dynamic conditions. The results revealed that both BSA and FBS slightly decreased the degradation rate of Mg in Hanks’ balanced salt solution (HBSS) under static immersion due to the protein adsorption and the formation of a Ca/P-rich top layer on Mg surface, whereas under dynamic flow condition the degradation of Mg was significantly accelerated in the presence of BSA or FBS. The reasons seemed to stem from the weakened protein adsorption on Mg surface in this case and the dynamically enhanced interaction between proteins and ions/products in solutions, which largely weaken the combination of the top Ca/P-rich layer with the inner corrosion product layer. These results highlight the importance of testing conditions for Mg characterization in vitro and the synergistic effect between different parameters on Mg degradation.