Fabrication of a ZnO/Polydopamine/ε-Polylysine Coating with Good Corrosion Resistance and a Joint Antibacterial Pathway on the Surface of Medical Stainless Steel

Medical stainless steel (SS) is a widely used alloy in orthopedic and dental implant applications. However, SS can cause local corrosion in the body, which may affect cell proliferation and differentiation, and is prone to related bacterial infection. Therefore, surface modification is required to improve the corrosion resistance and antibacterial performance of SS to extend its service life. To achieve this goal, a new type of composite coating was established on the surface of SS. First, zinc oxide (ZnO) nanoparticles were deposited on the surface of SS by electrochemical deposition. Then, polydopamine (PDA) was formed through the self-polymerization of dopamine. Finally, the Michael addition reaction between ε-polylysine (ε-PL) and PDA was used to chemically graft a cationic antimicrobial peptide (AMP), namely, ε-PL, constructing a corrosion-resistant and antibacterial ZnO/PDA/ε-PL coating on the surface of the SS (SZP/ε-PL). The results indicated that the obtained composite coating could significantly improve the corrosion resistance of SS because of the introduction of ZnO. After being irradiated with near-infrared (NIR) light (wavelength: 1064 nm, power: 1 W/cm²) for 8 min, the temperature of SZP/ε-PL increased from 22.4 to 57.8 °C. Moreover, there was no significant temperature decay after four cycles, which indicated the good photothermal performance and stability of SZP/ε-PL owing to the function of PDA. Combining photothermal sterilization and AMP contact sterilization, the antibacterial rates of SZP/ε-PL against <i>Escherichia coli</i> and <i>Staphylococcus aureus</i> both reached nearly 100%. In addition, SZP/ε-PL has excellent blood compatibility. With the above advantages, SZP/ε-PL was expected to become a safe and efficient implant material.