“Surface modification of Mg-Zn-Ca-Mn biodegradable biomaterials by ionic nitriding”

Background Magnesium-based alloys have emerged as promising biodegradable materials for temporary biomedical implants due to their biocompatibility, low density, and elastic modulus similar to natural bone. However, their rapid degradation in physiological environments limits their clinical application, making surface modification strategies necessary to improve corrosion resistance and mechanical performance. Objective The aim of this study was to evaluate the effect of ionic nitriding on the microstructure, corrosion resistance, mechanical properties, and cytocompatibility of Mg–Zn–Ca–Mn biodegradable alloys. Methods Mg–Zn–Ca–Mn quaternary alloys were synthesized by powder metallurgy and subsequently surface modified by ionic nitriding. The microstructure and phase composition were characterized using scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDS), and X-ray diffraction (XRD). Corrosion behavior was evaluated through electrochemical tests in Hank's solution, while mechanical properties were assessed using Vickers microhardness measurements. Cytocompatibility was analyzed by indirect cytotoxicity tests using fibroblast and keratinocyte cells. Results The nitrided alloys exhibited improved corrosion resistance, evidenced by lower corrosion current densities and more noble corrosion potentials compared with pure magnesium. In addition, ionic nitriding increased the Vickers microhardness by approximately 42–48%. Cytotoxicity assays showed that the Mg64–Zn30–Ca5–Mn1 alloy and its nitrided counterpart-maintained cell viability above 70%, indicating acceptable cytocompatibility. Conclusion Ionic nitriding is an effective surface modification technique to enhance the corrosion resistance, mechanical properties, and biological performance of Mg–Zn–Ca–Mn biodegradable alloys, demonstrating their potential for use as temporary biomedical implant materials.