Imidazolium ionic liquids as antimicrobial additives of biomedical PVC

In the last years ionic liquids (ILs) have attracted research interest for their thermal stability, non-inflammability, negligible vapour pressure, solvation ability, biocompatibility, low toxicity, etc . ILs based on imidazolium salts have been used in a wide range of biological and material science applicationsas scaffold for biomimetic applications, oxygen transport membranes, surfactants, plasticizers, antimicrobial and anti-inflamatory agents. It was reported that imidazolium ILs showed strong antimicrobial activity, comparable to that of commercial antimicrobial compounds such as Triclosan and that ILs biocidal activity is mainly due to the alkyl chain length in the cation. The aim of this study was the development of antimicrobial PVC compounds loaded with 1-10% (w/w) of 1,3-dimethyl5-sulfoisophthalate 1-hexadecyl-3-methyl imidazolium salt (PC4). PC4 was synthesised according to Colonna et al.4 and characterized by NMR and TGA. PVC-PC4 compounds were obtained by mixing, at 150 °C for 3 minutes, PVC pellets and PC4 powder (1-10% w/w ) in a Brabender mixer. Films of compounds were realized by compression moulding. Thermal and mechanical properties (elastic modulus E, tensile stress TS and elongation at break EB) of compounds were measured. Results demonstrated that the presence of PC4 in PVC formulation did not affect thermal and mechanical properties of compounds. The antimicrobial activity of PVC-PC4 compound films was determined by disk diffusion method. The inhibition zone (mm) surrounding the films, on TSA plates seeded with inocula of Escherichia coliand Staphylococcus epidermidisat an initial concentration of 103CFU/mL, was measured after 24 h of incubation at 37°C. Plates seeded with S.epidermidis showed an inhibition zone (6 mm) around PVC film containing 10% (w/w) of PC4, whereas no inhibition zonewas observed against E. coli growth, confirming a higher antimicrobial action against gram positive bacteria. In all cases there was no growth of these strains on the PVC-PC4 compound films.