Investigating the Self-Assembly of Steroidal Bio-surfactants in Deep Eutectic Solvents

Abstract

Deep Eutectic Solvents (DESs) have gained considerable attention as sustainable alternatives to conventional organic solvents. Since their introduction, research on the design, synthesis, physicochemical characterization, and wide-ranging applications of novel DESs has expanded exponentially [1]. Since the first evidence of self-aggregation of a surfactant in a DES in 2014 [2], investigation on the physicochemical properties of amphiphiles and their self-assembling behaviour in DESs has experienced a major upsurge. Despite escalating interest in this area, there remains a lot to explore about the ability of DESs to support diverse organized media, especially that of surfactants of biological origin. The interaction and self-association of steroidal bio-surfactants, also known as bile salts, in DESs remains a totally unexplored area and presents a novel opportunity to unravel the physicochemical behavior of these unconventional bio-surfactants in the neoteric greener solvents. The present work aims at investigating the self-assembling behaviour of bile salts in the choline chloride based DESs. Fluorescent bile acid derivatives have been used as system probes to get insight into the molecular level interactions. The results demonstrate that the rational engineering of DES composition offers a powerful approach to directing supramolecular architecture and self­assembly behavior of these amphiphiles (Fig.1 ).