A high throughput screen to test the biocompatibility of water-miscible ionic liquids

The Agar Diffusion test has been used for many years for testing antibiotic susceptibility in clinical laboratories. We wish to report that this simple, rapid test can also be applied to screen ionic liquids for toxicity to microorganisms. We screened 14 water miscible ionic liquids for toxicity for Clostridium butyricum using the test, and compared the results with EC(50) values calculated from measurements of growth rates in the presence of the ionic liquids. The Agar Diffusion test could be used reliably to identify ionic liquids which were toxic to C. butyricum, with EC(50) values below 0.034 M, and relatively non-toxic structures, with EC(50) values above 0.063 M. Therefore, the Agar Diffusion test can be used with confidence to distinguish between toxic and biocompatible ionic liquids.