Antimicrobial and antioxidant supramolecular ionic liquid gels from biopolymer mixtures

In this work, we describe the preparation and characterization of supramolecular ionic liquid gels based on binary mixtures of biopolymers, comprising chitosan, chitin, cellulose and lignin. The gels were obtained in ionic liquids differing in the cation or the anion, with no need for a cross-linking agent or acid treatment. The materials obtained were characterized for the minimum gelation concentration, porosity, swelling and rheological properties, finding a prominent influence of the nature of the ionic liquid anion. Then, we investigated the ability of the gels to scavenge free radicals, finding that the gels exhibit a higher antioxidant ability than their individual components. Moreover, our gels showed a bactericidal activity toward Gram-positive and Gram-negative bacterial strains like Streptomyces coelicolor and Escherichia coli, respectively. The kinetics of bacterial cell viability showed that the gel based on a chitosan : chitin mixture in the IL [bmim][Cl] was the fastest acting against E. coli, with a practically total killing of bacterial cells within 30 min. Once again, a major influence of the ionic liquid anion was detected. Finally, we found an inverse relationship between the antioxidant and antimicrobial activities of our gels.

Automated summary

We prepared and characterized supramolecular ionic liquid gels based on biopolymer mixtures without the need for a cross-linking agent or acid treatment. The gels showed notable properties influenced by the ionic liquid anion. They exhibited higher antioxidant ability and bactericidal activity compared to their individual components. The gel based on a chitosan:chitin mixture in the IL [bmim][Cl] had the fastest killing effect against E. coli, with almost complete eradication of bacterial cells within 30 minutes. We also observed an inverse relationship between the antioxidant and antimicrobial activities of the gels.