Lydie VIAU1, Hamdi BEN HALIMA1, Thibaut ZWINGELSTEIN2, Vincent HUMBLOT2, Boris LAKARD1
1Insitut UTINAM, Besanšon, France
2Institut Femto-ST, Besanšon, France
Since the discovery of their electrical properties in the 1970s, research interest in conductive polymers (CPs) has steadily increased. While most research on CPs focuses on microelectronic and optoelectronic applications, increasingly, researchers are applying the knowledge gained in these areas toward biomedical applications. The majority of these studies have used biocompatible polypyrrole (PPy) suitable for implantation into the body. At the same time, ionic liquids (ILs) especially those based on imidazolium cations showed promising application as novel antimicrobial agents. In particular, poly(ionic liquids) (PILs) have recently shown excellent antibacterial properties and their polymeric character has been used to manufacture antibacterial membranes. PILs that possess an intrinsically conducting polymers (ICP) backbone like polypyrrole have been synthesized with the objective to combine ionic and electronic conducting properties in the same polymers. However, to our knowledge polypyrrole-based PILs have never been explored as antibacterial materials.
In this study, we thus firstly prepared imidazolium-based ILs bearing a pyrrole function with different alkyl chain lengths and anions. The antibacterial activities of these monomers were investigated by means of their MIC/MBC (MIC = Minimal Inhibitory Concentration; MBC =Minimal Bactericidal Concentration) determination against Gram-negative E. coli and Gram-positive S. aureus. Our polypyrrole-PILs were then obtained by electropolymerization of the most promising monomers on FTO substrate. The resulting materials were thoroughly characterized by Scanning Electron Microscopy (SEM), X-ray photoelectron spectroscopy (XPS), Fourier-transform infrared spectroscopy (FTIR), profilometry, Glow Discharge Optical Emission Spectroscopy (GDOES) and Water Contact Angle (WCA) measurement. The antibacterial activities of the polypyrrole-PIL membranes were determined both by disk diffusion method and by the colony forming units (CFU) counting method over time. Our results evidenced excellent antibacterial activity for our polypyrrole-based PILs and this activity depends strongly on the alkyl chain length while metal-based anions are the most efficient ones.