Effects of 1-hexadecyl-3-methylimidazolium ionic liquids on the physicochemical characteristics and cytotoxicity of phosphatidylcholine vesicles

Abstract

This report is the first to study behaviors of nano-scale colloids prepared by long alkyl-chain imidazolium-based ionic liquids (LILs), namely, 1-hexadecyl-3-methylimidazolium hexafluorophosphate (C16MIMPF6) and 1-hexadecyl-3-methylimidazolium bromide (C16MIMBr), as well as phosphatidylcholines (PCs), including hydrogenated soybean phosphatidylcholine (HSPC) and egg phosphatidylcholine (EPC). The effects of LILs on the physicochemical characteristics of PC vesicles are investigated using morphological observations and measurements of particle size, zeta potential, and fluorescence polarization. The experimental data reveal that the incorporation of LILs into PC vesicles shows significant changes in the size, turbidity, zeta potential, storage stability, and membrane fluidity of colloids, which may be correlated with the counter-ions of the LILs, the degree of saturation of the PCs, and the vesicular composition. In addition, the cell viability of HaCaT, A431, and SCC25 cells decreases in a dose-dependent manner and is associated with the composition of the PC vesicles that are incorporated with LIL. The apoptotic characteristic of cells is more significant for the PC vesicles that incorporate a higher molar ratio of LILs at dispersion concentrations of 0.1 and 1mM. This work suggests that cytotoxicity is dependent on the counter-ions of LILs, the composition and concentration of dispersions, and the physicochemical properties of mixed LIL/PC colloids.