Toxicological evaluation on human colon carcinoma cell line (CaCo-2) of ionic liquids based on imidazolium, guanidinium, ammonium, phosphonium, pyridinium and pyrrolidinium cations

Toxicological evaluation of a new group of ionic liquids was performed on human colon cancerous cells—CaCo-2. They belong to different classes of cations: imidazolium (IM), dimethyl-guanidinium (dmg) and tetramethyl-guanidinium (tmg), methyl-pyrrolidinium (MPyr), 2-methyl-1-ethyl-pyridinium (2-MEPy), quaternary ammonium (benzyltriethyl-ammonium–BzTEA; phenyltrimethyl-ammonium–PhTMA; tri-n-octyl-methylammonium-Aliquat) and tri-n-hexyl-tetra-n-decylphosphonium (P6,6,6,14). The new results were compared with data obtained in previous reported studies performed in our lab, and we clearly saw that toxicity can vary significantly with the type of anion. Dicyanoamide-[DCA] and bis(trifluoromethanesulfonyl)amide-[NTf₂] were seen to visibly change the impact of some cations. Some were considerably less harmful for CaCo-2 monolayer when the anion was [DCA] or [NTf₂], while others induced an abnormal increase of cellular metabolism when [NTf₂] was present and therefore, they were considered toxic. However, some cations induced similar responses in the presence of a broad number of anions as (1-butyl-3-methylimidazolium)-[C₄MIM] (with the exception of [FeCl₄]), (1-(2-hydroxyethyl)-3-methylimidazolium)-[C₂OHMIM] and [C₄MPyr] and did not cause toxicity. Consequently, they are considered promising cations for building human friendlier solvents. But, a reasonable number of other combinations involving different classes of cations were also seen to not significantly affect viability of the CaCo-2 monolayer.