The effects of surface and biomolecules on magnesium degradation and mesenchymal stem cell adhesion

A novel class of biodegradable metals, magnesium (Mg) and Mg-based alloys, has recently attracted much attention because of unique biodegradation and mechanical properties for medical applications. Ideally, Mg-based devices should degrade no faster than the degradation products can be eliminated efficiently from the body. Additionally, for orthopedic and maxillofacial applications, the implant integration with the surrounding bone is critical for its clinical success. Therefore, it is necessary to thoroughly characterize Mg surface and degradation and investigate how these characteristics influence its interactions with essential cells, for example, bone marrow derived mesenchymal stem cells. The objectives of this study were to investigate (1) the effects of two surface conditions (the presence vs. absence of surface oxides) on Mg degradation and mesenchymal stem cell adhesion, and (2) the effects of two essential aqueous environments (the presence vs. absence of physiological ions and proteins) on Mg degradation. In an effort towards standardizing testing methods for Mg alloys, consistent and well-controlled experimental methods were designed to characterize the surface and degradation of Mg and its interactions with cells. The results demonstrated that original surface (oxidized vs. polished) conditions had a less pronounced effect on regulating initial cell adhesion, but did affect surface morphology and composition of the Mg samples after 24 h of cell culture. The presence versus absence of biological ions and proteins had a significant effect on Mg degradation mode and rate. In conclusion, the material surface and anatomical sites of implantation dependent on the intended applications must be carefully considered while assessing Mg alloys in vitro or in vivo for medical applications. Standardized testing procedures and methods are critically needed for developing more effective medical-grade Mg alloys.