Metal-polydopamine coordinated coatings on titanium surface: enhancing corrosion resistance and biological property

Abstract

Previous studies on polydopamine (PDA)-modified titanium implants have primarily focused on single-metal-ion systems (e.g., Ag⁺, Cu²⁺, or Zn²⁺), while overlooking the interplay between corrosion resistance, antioxidant retention, and antimicrobial efficacy under clinically relevant oxidative conditions. Here, we present a comparative analysis of Ag-, Cu-, and Zn-integrated PDA coatings fabricated via a two-step coordination strategy, addressing these limitations through systematic multi-parameter evaluation. Unlike prior studies, this study reveals distinct metal-PDA interaction mechanisms: XPS/EDS analyses confirm Zn²⁺ and Cu²⁺ form coordination complexes with PDA's catechol groups, whereas Ag⁺ undergoes reduction to metallic nanoparticles (Ag⁰), leading to divergent ion-release profiles (Zn²⁺ > Cu²⁺ > Ag⁺) and biofunctional outcomes. Electrochemical testing under H₂O₂-simulated oxidative stress demonstrates Zn-PDA coatings exhibit superior corrosion resistance (polarization resistance: 4330 vs. 3900 and 2850 kΩ cm² for Cu-PDA and Ag-PDA, respectively), while Ag-PDA achieves the highest antibacterial efficacy (>95% reduction against S. aureus and E. coli). Notably, Zn/Cu-PDA coatings retain >80% of PDA's intrinsic antioxidant capacity, in contrast to Ag-PDA, which exhibits significant antioxidant depletion due to redox interference. In vivo rat models further differentiate our approach: all coatings show comparable soft-tissue integration and systemic biosafety, contrasting with earlier reports of Ag-induced cytotoxicity. By elucidating metal-specific performance trade-offs and establishing a design framework to balance corrosion resistance, ROS scavenging, and antimicrobial activity, this work advances clinically adaptable strategies for enhancing peri-implant tissue stability.