Testing the antimicrobial properties of an upcoming “environmental-friendly” family of ionic liquids

The antimicrobial activity of a family of ionic liquids (discrete and polymerized) based on the [2- (methacryloyloxy)ethyl]dimethylheptyl ammonium cation and a series of anions, bis(trifluoromethylsulfonyl)-imide, nonafluoro-1-butanesulfonate, dodecylbenzenesulfonate, heptadecafluorooctanesulfonate, 4,4,5,5,6,6,7,7,8,8,9, 9,10,10,11,11,11-heptadecafluoro-undecanoate and decanesulfonate, was explored for potential application in the field of conservation of Cultural Heritage. The bio-activity was tested on four microbial strains isolated from deteriorated monuments: one GramNegative bacterial strain Stenotrophomonas maltophilia BC656, one Gram Positive bacterial species Micrococcus luteus BC657, one black yeast Aureobasidium pullulans MC852 and one dematiaceous hyphomycetes Cladosporium sp. MC853. Diffusion Agar tests showthat the bio-activity for this series of ILs ismainly determined by the anion lipophilicity, although the role of cations may be also envisaged. The dodecylbenzenesulfonate based IL shows the most significant antimicrobial activitywith an efficiency against the Gram Positive strain Micrococcus luteus higher than that of Preventol® 80 and Rocima™ 103 used as standards. The corresponding dodecylbenzenesulfonate polyionic liquid do not display both antibacterial and antifungal activity. This behavior is explained in terms of strongest electrostatic interactions operating between the polycation network and anion counterpart, making the active species less bio-available.