Impact of Surface-Active Guanidinium-, Tetramethylguanidinium-, and Cholinium-Based Ionic Liquids on Vibrio Fischeri Cells and Dipalmitoylphosphatidylcholine Liposomes

Abstract

We investigated the toxicological effect of seven novel cholinium, guanidinium, and tetramethylguanidinium carboxylate ionic liquids (ILs) from an ecotoxicological point of view. The emphasis was on the potential structure-toxicity dependency of these surface-active ILs in aqueous environment. The median effective concentrations (EC50) were defined for each IL using Vibrio (Aliivibrio) fischeri marine bacteria. Dipalmitoylphosphatidylcholine (DPPC) liposomes were used as biomimetic lipid membranes to study the interactions between the surface-active ILs and the liposomes. The interactions were investigated by following the change in the DPPC phase transition behaviour using differential scanning calorimetry (DSC). Critical micelle concentrations for the ILs were determined to clarify the analysis of the toxicity and the interaction results. Increasing anion alkyl chain length increased the toxicity, whereas branching of the chain decreased the toxicity of the ILs. The toxicity of the ILs in this study was mainly determined by the surface-active anions, while cations induced a minor impact on the toxicity. In the DSC experiments the same trend was observed for all the studied anions, whereas the cations seemed to induce more variable impact on the phase transition behaviour. Toxicity measurements combined with liposome interaction studies can provide a valuable tool for assessing the mechanism of toxicity.

Determination of the Main Phase Transition Temperature of Phospholipids by Nanoplasmonic Sensing

“…Therefore, DPPC in the fluid phase seemed to be more sensitive and less resistant to [P 14444 ][OAc] than DPPC in the gel phase. This is well in accordance with previous studies demonstrating that gel phase liposomes are less prone to interactions with external additives 63 – 65 .…”

Correlating Lipid Membrane Permeabilities of Imidazolium Ionic Liquids with Their Cytotoxicities on Yeast, Bacterial, and Mammalian Cells

“…The leakage assay clearly demonstrates that the longest-chain (and most hydrophobic) IL, [OMIM]Cl, permeabilizes model LUVs while the less hydrophobic, shorter-chain ILs do not. These results are similar to those reported in the literature using different ILs in which the cationic component was either choline, guanidine, or tetramethyl guanidine, and the anionic component contained variable alkyl chain lengths [28,53]. Recently, work from Wiedmer and coworkers also showed a strong correlation between hydrophobic content of a variety of ILs, interaction with model lipid vesicles, and cytotoxicity in mammalian and bacterial cells [54].…”

Correlation between Ionic Liquid Cytotoxicity and Liposome–Ionic Liquid Interactions

“…An increase in the concentration decreased the T m gradually and another endothermic peak appeared in the thermogram, proving an existence of two species in the system. Based on our earlier results, we assume that the main endotherm corresponds to the pure lipid bilayer without a remarkable amount of surfactants included, and the second endotherm at a lower temperature corresponds to newly formed mixed lipid–surfactant vesicles or a heterogeneous lipid–surfactant area in the otherwise pure liposome. In our previous study, we have shown that the lamellar distances of 1‐palmitoyl‐2‐oleyl‐phosphatidylcholine (POPC) multilamellar vesicles (MLVs) decrease and the lamellar disorder increases when [P 14 444 ][OAc] was added to the dispersion.…”