Redox-responsive ferrocene-containing poly(ionic liquid)s for antibacterial applications

Ferrocene (Fc)-containing imidazolium type ionic liquids (ILs) and corresponding poly(ionic liquid) (PIL) membranes with tunable antibacterial activity based on electrochemical redox reaction and host-guest chemistry were developed. The effect of Fc moiety on the antimicrobial activities against both Staphylococcus aureus (S. aureus) and Escherichia coli (E. coli) was studied by minimum inhibitory concentration (MIC). The presence of Fc groups highly enhanced the antibacterial efficiency of Fccontaining ILs because of the generation of reactive oxygen species (ROS). The electrochemical oxidation of Fc to Fc + and the formation of inclusion complexes between Fc and β-CD via host-guest interactions decreased the antibacterial activities of ILs and PIL membranes. The antibacterial activities may be recovered in some extent upon the electrochemical reduction of Fc + to Fc or the exclusion of the Fc out of the cavity of β-CD. Furthermore, all the Fc-containing PIL membranes showed relatively low hemolysis activities and none cytotoxicity toward human cells, indicating clinical feasibility in topical applications.