Ionic liquids are often praised for their green credentials, yet they can be highly toxic. Now, researchers from the University of Manchester, UK, have shown that the liquids' interactions with living cells can be studied using Fourier transform infrared (FT-IR) spectroscopy. Their aim is to help scientists understand ionic liquid toxicity mechanisms in order to design safer variants in the future.

Ionic liquids accumulate in the membranes of bacterial cells

Gill Stephens and colleagues used FT-IR spectroscopy to show that the more toxic of the ionic liquids that they studied accumulated in bacterial cells faster than the less toxic ones, suggesting that there may be a link. They also found that the compounds accumulated in the cell membranes, not the cytoplasm inside. Previous research has suggested that ionic liquid toxicity is due to the fact that they disrupt membranes, says Stephens, and these results provide direct support for that idea.

'I would be reluctant to say that this will be the only toxicity mechanism for ionic liquids though,' says Stephens. For example, ionic liquids can bond to enzymes and disrupt their structures, she explains. Research into this effect is ongoing in her laboratory.

Konrad Kulacki, at the University of Notre Dame, US, who studies the effects of ionic liquids on aquatic ecosystems, says that Stephens' work may help in assessing ionic liquids' environmental impact. 'It is important to study the mechanisms of ionic liquid toxicity, so we can use this information to design safer compounds,' he adds.

Reinforcing this point Stephens says that 'there are so many possible ionic liquid structures that finding ones with impeccable environmental credentials is like looking for a needle in a haystack.' Understanding exactly how the compounds affect living cells will therefore help to narrow the search, she says.

Danièle Gibney