A study on the interfacial chemistry of magnesium hydroxide surfaces in aqueous phosphate solutions: influence of Ca2+, Cl- and protein.

In recent years, magnesium based materials have been proposed as a potential biodegradable metallic implant material for orthopedic applications. Magnesium alloys are an excellent material for this purpose because they have mechanical properties that are similar to bone, have been shown to dissolve in biological fluids and are non-toxic. However, there is still relatively little information on the surface chemistry of these materials in physiological solutions. The interaction of phosphates with magnesium alloys is of particular interest because the deposition of calcium phosphate at implant surfaces is critical to the healing process in orthopedic applications. In the present work, the chemistry at the magnesium hydroxide/solution interface for model solutions containing physiologically relevant ions and protein was investigated using in situ ATR-FTIR. These studies are complemented by ex situ analysis of magnesium alloy coupons exposed to similar solutions. Our results demonstrate that precipitation of phosphate minerals at the solid/liquid interface dominates the observed changes in surface chemistry. The mineralization process was further observed to be strongly affected by the presence of chloride salts and protein in solution.