First investigation of liposomes behavior and phospholipids organization in choline chloride-based deep eutectic solvents by atomic force microscopy

Deep eutectic solvents (DES) have gained a lot of attention over the past years due to their numerous interesting properties. Despite being massively explored in various domains, there is still a need to understand the phospholipid self-assembly in these rising solvents. The present work aims to examine the phospholipids organization in four choline chloride-based DES (ChCl-DES) via atomic force microscopy (AFM). The effect of choline chloride:urea, choline chloride:glycerol, choline chloride:ethylene glycol, choline chloride:levulinic acid and the aqueous solutions of their individual components on E80 preformed liposomes was appraised for the first time. Lipid vesicles were formed 24 h after dissolving E80 phospholipids in the studied DES and their mean diameter was dependent on the partition coefficient logP of the hydrogen bond donor (HBD) component. When it comes to the effect on preformed liposomes, the size of the adsorbed liposomes was reduced after exposure to DES or to the aqueous solutions of their constituents. Similar results were observed when studying the dimensions of preformed liposomes in the aqueous solutions of DES components over time. However, when incubated in DES, liposomes were converted into supported lipid bilayers (SLB) before their reconstitution into vesicles. •Phospholipids form lipid vesicles in four choline chloride-based deep eutectic solvents (ChCl-DES).•ChCl-DES reduce the size of preformed lipid vesicles.•ChCl-DES effect on liposomes is time dependent.•Liposomes are converted to supported lipid bilayers before their reconstitution into vesicles in DES.