Biocompatibility of Mg biodegradable alloys and their importance in the medical applications and material science

Istrate Bogdan1, Munteanu Corneliu1,2 *

1 ”Gheorghe Asachi” Technical University of Iasi, Faculty of Mechanical Engineering, 63 D Mangeron Blvd, Iasi 700050, Romania.

2 Technical Science Academy Romania, 26 Dacia Blvd, Bucharest 030167, Romania

Previous studies on Mg-based biodegradable alloys of various ternary Mg-Ca-X systems, correlating biodegradation rate with osseointegration, found an increase in biodegradation time with the introduction of Mg-substituted elements. In this way, it was possible to correlate the biodegradation rate at different substitution values in order to reach an optimum for medical uses. Biodegradable magnesium alloys are suitable for ankle, foot, hand, and wrist implants, according to orthopedic implant research. Magnesium absorbs zinc (Zn), a crucial alloying component and its solid solution reinforcing and age-strengthening capabilities improves alloy`s mechanical properties. Also, Zn controls gene expression, anti-atherosclerosis, nucleic acid and protein creation, and nervous system function. Zirconium (Zr) is a magnesium grain refiner. In alloys with Zn, RE, Y, and Th, elements cannot be mixed with Al or Mn since these elements produce stable compounds with Zr. Magnesium is often combined with RE elements (Y) in order to improve its creep resistance and high-temperature strength. The excellent solubility enables Yttrium (Y) to dissolve, form solid solutions, and precipitate at grain boundaries. Mn refines microstructures and promotes germination during initial solidification and improves mechanical properties. Gadolinium (Gd) helps improve alloy strength but reduces ductility. 

This presentation will reveal results in terms of biocompatibility (in vitro/in vivo tests)of several Mg-Ca-X (where X= Zn, Zr, Y, Mn, and Gd) alloys. In vitro and in vivo biocompatibility tests show that, at optimal concentrations, the alloys are non-cytotoxic and promote bone integration and remodeling, with moderate inflammatory responses and progressive resorption. Mg-Ca-Mn and Zn-based alloys exhibit the highest biocompatibility.Hydrogen gas release was observed after implantation, which did not significantly affect tissue function, and the material resorption was almost complete after 8 weeks for the biodegradable alloys. Histological and imaging analyses confirm tissue integration, disappearance of inflammatory reactions, and efficient resorption of the biodegradable alloy over time.