title: Self-assembly and antimicrobial activity of long-chain amide-functionalized ionic liquids in aqueous solution.
abstract: Surface active amide-functionalized ionic liquids (ILs) consisting of a long alkyl chain (C6C14) connected to a polar head group (methylimidazolium or pyridinium cation) via an amide functional group were synthesized and their thermal stability, micellar properties and antimicrobial activity in aqueous solution investigated. The incorporation of an amide group increased the thermal stability of the functionalized ionic liquids compared to simple alkyl chain substituted ionic liquids. The surface activity and aggregation behaviour in aqueous solution of amide-functionalized ionic liquids were examined by tensiometry, conductivity and spectrofluorimetry. Amide-functionalized ILs displayed surface activity and their critical micelle concentration (cmc) in aqueous media decreased with the elongation of the alkyl side chain as occurs for typical surfactants. Compared to non-functionalized ILs bearing the same alkyl chain, ionic liquids with an amide moiety possess higher surface activity (pC20) and lower cmc values. The introduction of an amide group in the hydrophobic chain close to the polar head enhances adsorption at the air/water interface and micellization which could be attributed to the H-bonding in the headgroup region. The antimicrobial activity was evaluated against a panel of representative Gram-negative and Gram-positive bacteria and fungi. Amide-functionalized ILs with more than eight carbon atoms in the side chain showed broad antimicrobial activity. Antibacterial activities were found to increase with the alkyl chain length being the C12 homologous the most effective antimicrobial agents. The introduction of an amide group enhanced significantly the antifungal activity as compared to non-functionalized ILs.
authors.affiliation: Department of Chemical and Surfactant Technology, Institute of Advanced Chemistry of Catalonia IQAC-CSIC, Jordi Girona 18-26, 08034 Barcelona, Spain. Electronic address: teresa.garcia@iqac.csic.es.
authors.forename: M Teresa
authors.initials: MT
authors.lastname: Garcia
authors.affiliation: Department of Chemical and Surfactant Technology, Institute of Advanced Chemistry of Catalonia IQAC-CSIC, Jordi Girona 18-26, 08034 Barcelona, Spain.
authors.forename: Isabel
authors.initials: I
authors.lastname: Ribosa
authors.affiliation: Department of Chemical and Surfactant Technology, Institute of Advanced Chemistry of Catalonia IQAC-CSIC, Jordi Girona 18-26, 08034 Barcelona, Spain.
authors.forename: Lourdes
authors.initials: L
authors.lastname: Perez
authors.affiliation: Facultat de Farmacia, Universitat de Barcelona, Joan XXIII, 08028 Barcelona, Spain.
authors.forename: Angeles
authors.initials: A
authors.lastname: Manresa
authors.affiliation: Department of Chemical and Surfactant Technology, Institute of Advanced Chemistry of Catalonia IQAC-CSIC, Jordi Girona 18-26, 08034 Barcelona, Spain.
authors.forename: Francesc
authors.initials: F
authors.lastname: Comelles
mesh_terms: D000890:Anti-Infective Agents / Q000737:chemistry* / Q000494:pharmacology*; D005658:Fungi / Q000187:drug effects; D006090:Gram-Negative Bacteria / Q000187:drug effects; D006094:Gram-Positive Bacteria / Q000187:drug effects; D052578:Ionic Liquids / Q000737:chemistry*; D014867:Water / Q000737:chemistry*
chemical_list: D000890:Anti-Infective Agents; D052578:Ionic Liquids; D014867:Water
keywords: Aggregation behaviour; Antimicrobial activity; Functionalized ionic liquids; Surface activity