Water Induced Alterations in Self‐Assembly of a Bio‐Surfactant in Deep Eutectic Solvent for Enhanced Enzyme Activity

Abstract

AbstractDeep eutectic solvents (DESs) meet important requirements for green solvent technology, including non‐toxicity, biodegradability, sustainability, and affordability. Despite possessing low cohesive energy density than water, DESs have been found to support the self‐assembly of amphiphiles. It is very much pertinent to examine the effect of water on self‐assembly of surfactants in DESs as the presence of water alters the inherent structure of DES, which is expected to affect the characteristic properties of self‐assembly. Following this, we have investigated the self‐assembly of amino‐acid based surfactant, Sodium N‐lauroyl sarcosinate (SLS), in DES‐water mixtures (10, 30 and 50 w/w% of water) and explored the catalytic activity of Cytochrome‐c (Cyt‐c) in the formed colloidal systems. Investigations using surface tension, fluorescence, dynamic light scattering (DLS), and isothermal titration calorimetry (ITC) have shown that DES‐water mixtures promote the aggregation of SLS, resulting in the lower critical aggregation concentration (cac ∼1.5–6‐fold) of the surfactant as compared to water. The nanoclustering of DES at low water content and it's complete de‐structuring at high water content affects the self‐assembly in a contrasting manner governed by different set of interactions. Further, Cyt‐c dispersed in DES‐water colloidal solutions demonstrated 5‐fold higher peroxidase activity than that observed in phosphate buffer.