Magnetically-drivable, pH-responsive Fe3O4/ZIF-8 coating on implant for biofilm prevention and treatment

Antimicrobial coatings with the capabilities to prevent and treat biofilm infections on implant are promising surface treatment strategies, but it is difficult to eradicate an already-formed biofilm by the coating. Magnetically-drivable coatings can physically destruct the surface-attached biofilm to enhance antimicrobial killing. However, current magnetic coatings cannot inhibit the initial bacteria growth and the demand of coating stability restricts their magnetic controllability. Herein, a magnetically-drivable, pH-responsive coating is developed by simply mixing Fe₃O₄ and ZIF-8 nanoparticles on titanium surface. In physiological pH, Fe₃O₄ nanoparticles are stable and non-magnetically drivable on surface due to charge attractions and electrostatic interactions. While in acidic pH caused by bacterial growth, ZIF-8 degradation is significantly accelerated, releasing Zn^2 + and recovering the magnetic controllability of Fe₃O₄ nanoparticles. The released Zn²⁺ kills the initially-attached bacteria, inhibiting subsequent biofilm formation. Once a biofilm has formed, Fe₃O₄ nanoparticles can be magnetically pulled-off to destruct the biofilm structure and then enhance antibiotic killing. The Fe₃O₄/ZIF-8 coating shows excellent biocompatibility and osteogenesis to compare with bare Ti disc. Animal experiments further proved the in-vivo antimicrobial and osteogenic performances of the coating. Therefore, this work put forward a new surface strategy to solve biofilm-related infections on implants.