Spontaneous and Biomimetic Apatite Formation on Pure Magnesium

Abstract

In order to decrease its degradation rate, pure magnesium was subjected to the following treatments: (1) heat treatment at 345oC for 15 min and (2) heat treatment at 380°C for 30 min followed by hot rolling at 350°C. The treated samples and non-treated controls were immersed in simulated body fluid (SBF) at 37oC for different periods of time. In all cases, the magnesium released into the SBF, the weight loss of the specimens and the pH of SBF increased with time of immersion. The hot-rolled samples showed a lower degradation rate and lower pH values. A lower increase of magnesium concentration in the SBF corresponding to the hot-rolled samples was also observed. The main and unexpected positive finding of this work was that in all cases, a layer of Ca, P-rich was formed on the substrates after only 3 days of immersion in SBF. This indicates that metallic magnesium is a potential bioactive material. In the aim to promote the formation of a thicker bioactive layer than the one observed on the samples immersed in single SBF, hot-rolled magnesium was biomimetically-treated using wollastonite ceramics, SBF and a more concentrated solution (1.5 SBF). A homogeneous and dense bone-like apatite layer was observed on the biomimetically-treated samples.