ANTIBACTERIAL ACTIVITY OF POLYMER COMPOUNDS BASED ON IMIDAZOLIUM IONIC LIQUID

Microbial contamination represents a severe problem in many sectors, including medical, industrial, food and domestic fields. Moreover, the increasingly widespread of antibiotic resistance is becoming a great concern for public health, in particular for hospitals. In order to avoid the excessive use of antibiotics, researches on alternative biocides are increasing. Among alternatives, ionic liquids (ILs), low temperature molten salts, and in particular imidazolium ILs have been studied for a wide range of biological applications to produce surfactants, oxygen transport membranes, scaffold for biomimetic applications, plasticizers, antimicrobial and anti-inflammatory agents [1]. The aim of this study was the realization of antimicrobial compounds based on Polyvinyl Chloride (PVC), Styrene-Butylene-Ethylene-Styrene (SEBS) and Low-Density Polyethylene (LDPE), loaded with different concentrations (1, 5 and 10%) of the ionic liquid (IL) 1-hexadecyl-3-methyl imidazolium 1,3-dimethyl 5-sulfoisophthalate (Hdmim DMSIP). The antibacterial activity of compounds was evaluated against two human pathogenic bacteria, Staphylococcus epidermidis and Escherichia coli. The IL was synthetized according to Colonna et al. [2], with slight modifications, and characterized by 1HNMR, MALDI TOF, TGA and DSC. The antimicrobial compounds were obtained by mixing polymer matrices with the IL in a Brabender mixer, adopting suitable operative conditions for each polymer. Film compounds were obtained by compression molding at 150 °C for PVC/IL, whereas those of LDPE/IL and SEBS/IL were realized at 180 °C. The antibacterial activity of film samples were determined by disk diffusion test. Results showed an excellent antimicrobial activity of neat IL vs S. epidermidis, with MIC value of 10 µg/ml, whereas its activity vs E. coli indicated a lower sensitivity of this strain (MIC of 100 µg/ml). The introduction, at different concentrations, of this IL into polymer matrices, highlighted different behaviors depending on structure and physical-chemical properties of the tested polymers, which may facilitate its release and diffusion in TSA. Both PVC/IL and SEBS/IL compounds showed a good antimicrobial activity against S. epidermidis growth at all concentration of IL loaded, whereas the LDPE/IL compound exhibited antibacterial activity against S. epidermidis only at the highest concentrations (5-10%). In all experiments, the antimicrobial activity of the compounds against E. coli growth was lower than that displayed against S. epidermidis, confirming a higher sensitivity of Gram-positive bacteria towards imidazolium based ionic liquids with long alkyl chain.