Osteogenic and antibacterial coating containing strontium and calcium on zinc implants via redox-assisted...

Biodegradable zinc (Zn)-based implants are emerging as one of the leading candidate materials for orthopedic applications owing to their favorable degradation behavior and mechanical properties; however, their clinical translation is delayed by insufficient surface bioactivity. In this study, a multifunctional composite coating incorporating strontium (Sr) and calcium (Ca) was fabricated on Zn implants via a redox-assisted co-deposition strategy. This method harnesses the strong oxidizing power of permanganate to controllably dissolve the Zn substrate, facilitating the gradient incorporation of Ca²⁺ and Sr²⁺ through hydroxyl-mediated cross-linking and resulting in a composite structure with a concentration gradient. The process is completed within 30 min under mild temperature and atmospheric pressure without the need for specialized equipment. The coating operates through a dual mechanism: it regulates the degradation behavior of the Zn substrate and modulates Zn²⁺ release kinetics to mitigate cytotoxicity from excessive local ion concentrations, while simultaneously leveraging the synergistic effects of Ca²⁺ and Sr²⁺ to enhance hemocompatibility and long-term cytocompatibility. Moreover, the coating promotes osteogenic activity by activating osteogenesis-related signaling pathways and stimulating cell adhesion, spreading, migration, and differentiation, alongside conferring antibacterial properties, thus achieving a balanced osteogenic-antimicrobial functionality. This surface modification strategy offers a novel and scalable approach for engineering biodegradable Zn-based implants, demonstrating strong potential for clinical translation in orthopedics.