Inhibiting insulin aggregation by chaperone-like green cholinium-based DESs as additives

Protein microenvironment is critical to study protein function and stability, which crucially depend on their interaction with co-solvents. In the current study, the ability of synthesized choline-based deep eutectic solvents (DESs) as additives to inhibit and disaggregate amyloid fibrils of human insulin was investigated. The DESs synthesized in this study were nontoxic and can be classified as green chemistry. Utilizing various biophysical methods indicated that choline-chloride glycine (Ch/Gly) and choline-chloride ascorbic acid (Ch/Asb) exhibited chaperone-like properties. This was attributed to their inhibitory effects on the lag phase by stabilizing insulin monomers and on the saturation phase by disaggregating mature insulin fibrils. In contrast, choline-chloride histidine (Ch/His) accelerated the aggregation of insulin. Our results suggest that antioxidant and hydrophobic properties combined with lower surface activity and higher hydrogen bond formation ability, are the main features describing the inhibitory effect of DESs on protein aggregation.