The advent of three-dimensional (3D) printed porous Mg alloys is considered a significant milestone in the development of metal-based degradable implants. However, the poor corrosion resistance of additively manufactured Mg alloys, along with the occurrences of inflammation and bacterial infections following implantation, pose critical challenges. In this study, two drug-loaded coatings were prepared within a porous Mg alloy using in situ incorporation and post-deposition of layered double hydroxides (LDHs) to enhance corrosion resistance, antibacterial properties, and biological compatibility combined with plasma electrolytic oxidation (PEO). The results revealed that in situ incorporation of LDH capsules effectively reduced the porosity of the PEO layer and improved the long-term corrosion resistance of the coating. The post-deposited LDH layer effectively sealed the PEO layer, demonstrating highly stable corrosion resistance during 7 d electrochemical impedance spectroscopy (EIS) test, with the impedance modulus at 10^–2 Hz stabilizing at 5 × 10⁵ Ω·cm². After soaking, the surface morphology of the in situ drug-loaded PEO coating exhibited more cracks and defects, whereas the PEO-LDH coating maintained a relatively dense morphology. Among the tested samples, the PEO-LDH coating showed the best performance in terms of corrosion resistance, cell proliferation and differentiation capabilities, and antibacterial efficacy (>99%). Its strong compatibility with the porous structure of 3D-printed Mg alloy highlights the potential of this coating system for biomedical applications. The design strategy proposed in this study offers valuable insights for future development of drug-loaded coatings for 3D-printed porous materials.

A gradient coating containing collagen and inorganic strontium/calcium phosphate (Sr/CaP) was fabricated on plasma-electrolytically oxidised magnesium via one-step cathodic electrodeposition. First, Sr-doped dicalcium phosphate dihydrate and hydroxyapatite (DCPD and HA) was deposited, followed by a collagen/CaP layer. The morphological evolution, sequential degradation behaviour, and in vitro bio-properties of the coatings were investigated. The incorporation of collagen remarkably refined the morphology of the CaP, and a more aggregated nano-spherical morphology was observed with increasing collagen concentration. Sr could partially replace Ca in the CaP crystals. Collagen combined with CaP formed a relatively stable skeletal frame, which provided sufficient barrier properties and more sites for the re-precipitation of bone tissue, as well as a more promising proliferation and differentiation ability of osteoblasts. A gradient coating that matches the requirements of bone growth at various periods is suggested for implantation.