Anti-corrosion and cytotoxicity properties of inorganic surface treatments on Mg1Ca biodegradable alloy

In this work biodegradable Mg1Ca alloy underwent surface modification using hydroxyapatite (HAp), aluminium oxide (Al2O3), and treatments with phosphoric (H3PO4), hydrofluoric (HF), and acetic (CH3COOH) acids. The resulting surface-treated Mg substrates were assessed in terms of phase content and chemical composition through X-ray diffraction (XRD) and glow discharge optical emission spectrometry (GDOES). Additionally, atomic force microscopy (AFM) and scanning electron microscopy (SEM) were employed to examine the surface's topography and structure, while the corrosion behavior and cytotoxicity were surveyed using electrochemical impedance spectroscopy (EIS), alongside WST-1 reduction and lactate dehydrogenase (LDH) release assays on L929 mouse fibroblasts. The findings indicated that the surfaces of all samples were uniformly structured, while chemical analysis of the treated surfaces suggested the presence of mostly thin films. Furthermore, EIS results highlighted that the HAp-treated Mg1Ca alloy exhibited superior corrosion resistance, and the cytotoxicity assessment of Mg1Ca-HAp and Mg1Ca-H3PO4 alloys showed minimal cytotoxic effects on mouse fibroblasts, compared to other treated surfaces, suggesting enhanced biocompatibility of those two surface treatments. Overall, this constitutes the first comparative study of different surface treatments developed on biodegradable Mg1Ca alloy, aiming to identify optimal modification strategies for biomedical applications.

Highlights: -Different surface treatments were applied to biodegradable Mg1Ca. -Most treatments resulted in thin, amorphous films, which altered chemical composition and, in some cases, topography. -The best corrosion protection was achieved with hydroxyapatite conversion film. -Phosphoric acid and hydroxyapatite-based treatments showed the lowest cytotoxicity among the studied treatments.