Rare-earth-doped MgZnCa metallic glass with tailored corrosion behavior and improved in vivo biocompatibility

The study incorporates the rare earth elements yttrium (Y) and gadolinium (Gd) into a (Mg-Zn-Ca) metallic glass (MG) system. In vitro experiments are performed to examine the corrosion behavior and mechanisms in simulated bodily fluid (SBF) settings utilizing phosphate buffered saline (PBS) and simulated inflammatory conditions employing H₂O₂-PBS solution. Simultaneously, utilizing additive manufacturing technology, polyetheretherketone (PEEK) scaffolds are fabricated, and rare earth Y/Gd-doped MgZnCa amorphous coatings are applied to the scaffolds via magnetron sputtering, with the objective of enhancing the biological activity of bone repair at the atomic level. The Mg-Zn-Ca-Gd system has an elevated self-corrosion potential (E_corr) and diminished corrosion current density (I_corr) in both solutions, accompanied by a reduced corrosion rate, as evidenced by electrochemical and SEM experimental characterisation. In PBS solution, the Mg-Zn-Ca-Y alloy system experiences surface degradation due to chloride ion infiltration into the passivation layer; in the H₂O₂-PBS solution, the corrosion products on the surface of Mg-Zn-Ca-Gd are more compact, whereas numerous corrosion pits and cracks manifest on the surface of Mg-Zn-Ca-Y. Cellular and in vivo tests on mice have demonstrated that Y-doped MgZnCa amorphous coatings have superior bone regeneration benefits. The Y element accelerates the nucleation of mineralized cores, hence enhancing the degree of bone mineralization. The greater hydrated ionic radius of the Gd element diminishes transmembrane transport efficiency. Moreover, Mg-Zn-Ca-Gd has superior corrosion resistance, resulting in diminished release of Gd³⁺ during physiological activities, and hence impeding the regulation of bone and cartilage function by Ca²⁺. This study clarifies the method by which rare earth elements are incorporated to improve the corrosion resistance of magnesium-based metallic glasses, offering a viable composite material option for the application of metallic glasses in orthopedic implants and other domains.