Formation and potential application of micelles composed of biocompatible N-lauroyl-amino acid ionic liquids surfactant

Surface-active ionic liquid (SAIL) surfactants have attracted attention as promising alternatives to conventional surfactants because of their tailor-made and tunable properties. SAILs also address the limitations associated with conventional surfactants including toxicity and formation of unstable micelles. Here, we investigated the aggregation behavior of three biocompatible choline N-lauroyl-amino add (NIAA)-based ILs with different amino acid side chains in aqueous solutions. The micellar behaviors of NLAA-ILs were investigated using surface tensiometry, conductometry, dynamic light scattering (DLS) and transmission electron microscopy (TEM). The critical micellar concentration (CMC) of the NLAA-ILs was found to be 2 to 4-fold lower compared with the conventional surfactant sodium dodecyl sulfate (SDS). The thermodynamic behavior confirmed that the micelle formation of NLAA-ILs was stable, spontaneous and entropy driven at room temperature. DLS and TEM studies revealed that the size and shape of the micelles depended on the presence of an N-hydrogen group in the head group of the anion. Choline N-lauroyl glycinate ([Cho][NLG]) and dicholine N-lauroyl aspartate ([Cho](2)[NLA]) were predominantly produced as unilamellar vesicles in water whereas choline N-lauroyl sarcosinate ([Cho][NLS]) formed small spherical micelles. Importantly, SAIL [Cho][NLG] showed lower toxicity toward mammalian cells compared with the analogous Rs or the conventional surfactant SDS and similar toxicity to the conventional surfactant Tween 80. SAIL [Cho][NLG] was more efficient at forming hydrophobic ion pairs with the macromoleadar drug heparin compared with SAIL [Cho][NLS]. These results clearly suggest that the biocompatible NLAA-ILs represent promising potential substitutes for conventional surfactants in various biomedical applications. (C) 2020 Elsevier B.V. All rights reserved.