Microstructural, Electrochemical and In Vitro Analysis of Mg-0.5Ca-xGd Biodegradable Alloys

The subject of Mg-based biodegradable materials, used for medical applications, has been extensively studied throughout the years. It is a known fact that alloying Mg with biocompatible and non-toxic elements improves the biodegradability of the alloys that are being used in the field of surgical applications. The aim of this research is to investigate the aspects concerning the microstructure, electrochemical response (corrosion resistance) and in vitro cytocompatibility of a new experimental Mg-based biodegradable alloy—Mg–0.5%Ca with controlled addition of Gd as follows: 0.5, 1.0, 1.5, 2.0 and 3.0 wt.%—in order to establish improved biocompatibility with the human hard and soft tissues at a stable biodegradable rate. For this purpose, scanning electron microscopy (SEM), energy-dispersive spectroscopy (EDS), light microscopy (LM) and X-ray diffraction (XRD) were used for determining the microstructure and chemical composition of the studied alloy and the linear polarization resistance (LPR) method was used to calculate the corrosion rate for the biodegradability rate assessment. The cellular response was evaluated using the 3-(4,5-dimethyltiazol-2-yl)-2,5-diphenyl tetrazolium bromide (MTT) test followed by fluorescence microscopy observation. The research led to the discovery of a dendritic α-Mg solid solution, as well as a lamellar Mg2Ca and a Mg5Gd intermetallic compound. The in vivo tests revealed 73–80% viability of the cells registered at 3 days and between 77 and 100% for 5 days, a fact that leads us to believe that the experimental studied alloys do not have a cytotoxic character and are suitable for medical applications.