Ionic liquids affect the adsorption of liposomes onto cationic polyelectrolyte coated silica evidenced by quartz crystal microbalance

Abstract

The worldwide use of ionic liquids (ILs) is steadily increasing, and even though they are often referred to as "green solvents" they have been reported to be toxic, especially toward aquatic organisms. In this work, we thoroughly study two phosphonium ILs; octyltributylphosphonium chloride ([P8444]Cl) and tributyl(tetradecyl)phosphonium chloride ([P14444]Cl). Firstly, the critical micelle concentrations (CMCs) of the ILs were determined with fluorescence spectroscopy and the optical pendant drop method in order to gain an understanding of the aggregation behavior of the ILs. Secondly, a biomimicking system of negatively charged unilamellar liposomes was used in order to study the effect of the ILs on biomembranes. Changes in the mechanical properties of adsorbed liposomes were determined by quartz crystal microbalance (QCM) measurements with silica coated quartz crystal sensors featuring a polycation layer. The results confirmed that both ILs were able to incorporate and alter the biomembrane structure. The membrane disrupting effect was emphasized with an increasing concentration and alkyl chain length of the ILs. In the extreme case, the phospholipid membrane integrity was completely compromised.

Edible film incorporated with chitosan and Artemisia annua oil nanoliposomes for inactivation of Escherichia coli O157:H7 on cherry tomato

“…QCM‐D was performed with QSX 301 Gold sensors on a Q‐Sense E4 instrument and an Ismatec IPC‐N Pump (set to 50 μL min −1 ) (Q‐Sense E4, Biolin Scientific Co., Ltd, Vasteras, Sweden). 0.5 mL of sample was introduced after the system was rinsed with 0.03 m PBS buffer for 40 min (Duša et al ., ).…”

Correlation between Ionic Liquid Cytotoxicity and Liposome–Ionic Liquid Interactions

“…Critical micelle concentration determinations : The critical micelle concentration (CMC) determinations of [Ch][Hex] and [N 4441 ][OAc] in water were performed using a contact angle meter (CAM 200 Optical Contact Angle Meter, Biolin Scientific, KSV Instruments, Finland) measuring the surface tension of a drop upon an increasing concentration of the IL (optical pendant drop method). The method is described in more detailed in our previous articles …”

Effects of phosphonium-based ionic liquids on phospholipid membranes studied by small-angle X-ray scattering

“…Zeta potential measurements were conducted at 20 °C, and a dielectric constant of 80.4 (for water) and a viscosity value of 1.0031 cP (for water) were used in the calculations. The applied electric field strength was 150 V·cm (Dusa et al, 2015) and that of [P14444][OAc] is 0.89 mM in water and 0.32 mM in sodium phosphate buffer (pH 7.4; ionic strength 10 mM) (Ruokonen et al, 2016 [OAc] resulted in a decrease of the intensity, as seen when comparing the intensities of the first and second diffraction peak to the reference. Despite this, the size of the scattering 205 region (the correlation length in the direction of membrane normal), as determined from the FWHM of these peaks, changed only little in all the samples.…”

“…The toxicity results from human corneal epithelial cells and E. coli cells correlated with changes in the liposome surface charge and shape, indicating that the cytotoxicity is in part due to interactions between the ILs and the phospholipid bilayer. The concentration at which ILs start to form micelles (critical micelle concentration, CMC) correlates well with the concentration at which the ILs start to disrupt unilamellar vesicles (LUV) (Dusa et al, 2015;Ruokonen et al, 2016). Clearly, the effects 70 of ILs on lipid bilayers are more destructive at concentrations where IL micelles form.…”