Effects of different head groups and functionalised side chains on the cytotoxicity of ionic liquids

Abstract

To enlarge the restricted knowledge about the hazard potentials of ionic liquids to men and the environment we have concentrated on systematically analysing the effects of 7 head groups, 10 side chains (mainly containing functional groups) and 4 anions on cytotoxicity. For our investigations, we used the promyelotic leukemia rat cell line IPC-81 as test system, with the reduction of the WST-1 dye as an indicator of cell viability. Our results show that most of the tested 100 ionic liquids generally exhibit a low cytotoxicity compared to previously investigated ionic liquids in consequence of their polar ether, hydroxyl and nitrile functional groups within the side chains. Those functional groups hamper cellular uptake by membrane diffusion and reduce lipophilicity based interactions with the cell membrane.

In general, a low influence of the head group and a clear anion effect of the [(CF₃SO₂)₂N]⁻ anion could be observed. Furthermore, we could confirm the general dependency between ionic liquid cation lipophilicity and cytotoxicity using a HPLC derived lipophilicity parameter. For one head group and for one side chain, deviations were obtained concerning this general dependency. This can be interpreted as a first hint for a more specific mode of action for these structural elements.