Recent progress in smart coatings for Mg implants: Functional strategies for corrosion protection
Helia Heydarinasab, H. Eivaz Mohammadloo
Abstract
Magnesium and its alloys have emerged as promising candidates for next-generation biomedical implants, offering low density, mechanical compatibility with bone, and biodegradability, making them suitable for temporary devices such as orthopedic fixation systems and cardiovascular stents. However, rapid and uncontrolled corrosion in physiological environments remains a major challenge, leading to risks such as structural failure, local alkalization, hydrogen gas evolution, and potential cytotoxicity from ion release. To address these limitations, advanced smart coatings have been developed to provide more than passive protection. These functional coatings enhance corrosion resistance and introduce adaptive behaviors, enabling implants to respond to damage or environmental changes through features like self-healing, superhydrophobicity, anti-fouling properties, and shape-memory effects. Multilayer composite coatings—combining advanced rare-earth-doped micro-arc oxidation (MAO) (e.g., cerium-doped MAO, graphene oxide-MAO, hydroxyapatite-MAO), task-specific ionic liquids (e.g., [OTP][NTf 2 ], [EMIm][NTf 2 ], [EBPz][NTf 2 ], amino-acid-functionalized ILs), eco-friendly fluorine-free superhydrophobic polymers (e.g., layer-by-layer nanostructures, polysiloxane coatings, MOF-derived surfaces), supramolecular self-healing polyurethanes (e.g., cyclodextrin–adamantane systems, disulfide exchange, Diels–Alder networks), and advanced corrosion inhibitors (e.g., 8-hydroxyquinoline (8-HQ), benzotriazole, cerium salts)—have demonstrated remarkable corrosion resistance and long-term stability, even after surface damage. This review explores advanced smart coatings for magnesium implants, emphasizing their functional mechanisms, material design, and biological performance, with a focus on multifunctional systems integrating structural strength and bioactivity. By highlighting transformative trends and key innovations in the field, this article aims to map the future landscape of bioresorbable, intelligent implant coatings—where surface engineering meets adaptive healing.