pH-responsive d-leucine functional multilayer films with antibacterial and anti-adhesion synergistic properties

Bacterial infections, as one of the main reasons for failure of metallic implants, can increase morbidity and mortality. In this study, polydopamine/graphene oxide- d -leucine (PDA/GO-Leu) films that possess pH-responsive antibacterial and anti-adhesion properties were synthesized by the soaking method. Due to the unique features of ampholyte, d -leucine has the same type of charge as the immobilized GO surface when the pH value of the environment is identical to that of the humoral environment. It contributes to the d -leucine release from the GO surface and exerts antibacterial and anti-adhesion effects of such films. The synergistic actions between d -leucine and GO of such films were analyzed by the table colony counting method and dead/live fluorescence. The results indicated that the released d -leucine is the key point within this multilayer system. The PDA/GO-Leu films exhibited both outstanding antibacterial and anti-adhesion properties for E. coli and S. aureus, respectively when pH of the culture medium was 7.4. Meanwhile, the cytotoxicity of the PDA/GO-Leu films was evaluated by CCK-8 and dead/live fluorescence, and the results demonstrated that such films have good biocompatibility.