Hospital cleaners may one day use ionic liquids to clean wards. Brendan Gilmore and co-workers at the Queen's University, Belfast, UK, have shown that the compounds are effective antibacterial agents that can be used to break down microbial biofilms, a cause of hospital acquired infections such as MRSA.

Ionic liquids are low temperature molten salts formed from cations and anions. While ionic liquids must be tested for environmental toxicity before they can be used as safer alternatives to industrial solvents, Gilmore is using their toxicity for the benefit of human health. 'Altering the cation and anion pairing allows you to tune the toxicity,' says Gilmore.

Gilmore tested the effects of 1-alkyl-3-methylimidazolium chloride ionic liquids on the bacterial biofilms of several pathogens including methicillin-resistant Staphylococcus aureus and Escherichia coli. The team found that antibiofilm potency increased with the length of the alkyl chain. Biofilms are bacterial communities that enclose themselves in a protective polymer. They are more resistant to antibiotics or other sterilisation methods than their free-swimming counterparts. 'Resistance to antimicrobials is an increasing global threat to public health,' says Jan Michiels, an expert in biofilms at the Catholic University of Leuven, Belgium. Ionic liquids could be applied to a surface already hosting a biofilm to help sterilise it, but Gilmore says he hopes that ionic liquids will be used to coat surfaces to prevent biofilms forming. 

According to Gilmore, the advantages might not be limited to the health sector. Microbial biofilms can foul pipes in industrial machinery, and marine antifouling - a coating painted on to the hull of ships - could be another potential application.

Gilmore's team is currently working on novel ionic liquids with improved antimicrobial and antibiofilm activities.

Russell Johnson

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