Alkylimidazolium ionic liquids for biofilm control: Experimental studies on controlling multispecies biofilms in natural waters

Abstract

Biofilm associated problems and inherent resistance of biofilm-bacteria to antimicrobial agents drives the need for alternate agents with potent antibiofilm activities. Alkylimidazolium ionic liquids were reported as novel antimicrobial and antibiofilm agents for preventing single species biofilms. However, naturally occurring biofilms are multispecies in nature constituting diverse organisms and have high prevalence, significance in medical, industrial and ecological perspective. In this study, the effect of three alkylimidazolium ionic liquids ([CnMIM]+[X]−, n = 4, 12 and 16) were evaluated against formation of natural and multispecies biofilms in freshwater and seawater. In 96-well biofilm assays, [C4MIM][Cl] with –butyl alkyl group did not exert antibiofilm activity even at 500 µM. [C12MIM][I] with –dodecyl alkyl group showed antibiofilm activity at 32 and 250 µM, in natural freshwater and seawater, respectively. Among the tested ionic liquids, [C16MIM][Cl] with –hexadecyl group showed superior antibiofilm activity. Presence of [C16MIM][Cl] in freshwater and seawater, respectively, at 8 and 125 µM caused complete inhibition in biofilm formation. Among the tested compounds, only [C16MIM][Cl] showed biofilm dispersal activity on pre-formed biofilms. Biofilm dispersal was near complete at 125 and 250 µM for freshwater and seawater biofilms, respectively. Potent antimicrobial ionic liquid ([C16MIM][Cl]) was further evaluated for biofilm prevention under dynamic conditions in a laboratory scale recirculation system. Over a period of 12 d of operation, biofilm formation was retarded in the presence of 100 μM and 250 μM of [C16MIM][Cl], in freshwater and seawater, respectively. The results suggest that antimicrobial [C16MIM][Cl] may find potential application for preventing multispecies biofilms in cooling water systems.