Thermodynamics and structure of model bio-membrane of liver lipids in presence of imidazolium-based ionic liquids

Ionic liquids (ILs) are the attractions of researchers today due to their vast area of potential applications. For biomedical uses, it becomes essential to understand their interactions with cellular membrane. Here, the membrane is mimicked with lipid bilayer and monolayer composed of liver lipids extract. Three archetypal imidazolium based ILs, 1-decyl-3-methylimidazolium tetrafluomborate ([DMIM][BF4] or [C10MIM][BF4]), 1-octyl-3-methylimidazolium tetrafluoroborate, ([OMIM][BF4] or [C8MIM][BF4]) and 1-ethyl-3-methylimidazolium tetrafluoroborate ([EMIM][B3F4] or [C2MIM][BF4]) having different alkyl chain lengths are used in the present study. The isothermal titration calorimetry (ITC) measurements showed that [DMIM][BF4] interacts strongest with the liver lipid membrane compared to other two ILs which have relatively shorter alkyl chain length. The low values of stoichiometry ratio of ILs indicates that ILs penetrate within the core of the lipid bilayer. The interaction of ILs with the liver lipid membrane is found to be mainly driven by entropy which could be due to the change in the structure of the lipid membrane at local or global scales. Dynamic light scattering (DLS) measurements indicate that there are no changes in the size of vesicles due to addition of [DMIM][BF4] indicating stability of the vesicles. On the other hand, x-ray reflectivity (XRR) measurements showed a concentration dependent change in the monolayer structure. At low concentration of the IL, the monolayer thickness decreases, exhibiting an increase in the electron density of the layer. However, at higher concentrations, the monolayer thickness increases proving a concentration dependent effects of the IL on the arrangement of the molecules.

Automated summary

Ionic liquids (ILs) are currently attracting researchers due to their potential applications in various fields. In biomedical research, understanding the interactions between ILs and cellular membranes, mimicked with lipid bilayers and monolayers, is crucial. Among the three imidazolium-based ILs studied, [DMIM][BF4] showed the strongest interaction with liver lipid membranes. This interaction is mainly driven by entropy and results in ILs penetrating the core of lipid bilayers. Dynamic light scattering (DLS) measurements suggest that [DMIM][BF4] does not affect the stability of lipid vesicles, while X-ray reflectivity (XRR) measurements reveal a concentration-dependent change in monolayer structure.