Structural stability of insulin aspart in aqueous cholinium aminoate ionic liquids based on molecular dynamics simulation studies

Conformational stability is an important criterion for proteins applied in food, biopharmaceutical, and biochemical industries. The fluctuations of temperature during production, transit, and storage of proteins tend to alter the inherent structure and biological activity of proteins. Among the chemical additives explored for the stabilization of proteins, cholinium-based ionic liquids (ILs) have emerged as a promising solvation medium to preserve the native structure of proteins. By pairing with the amino acids as an anionic counterpart, the cholinium aminoates have a good biocompatibility for biopharmaceutical applications. Using molecular dynamics simulations, we investigated the stability of insulin aspart, a protein-based drug, in cholinium aminoates made of different amino acids. Our simulation results revealed for the first time that the structural stability of insulin aspart in aqueous solution containing cholinium prolinate ([Ch][Pro]) was exceptionally high. The stabilizing effect was mainly contributed by the large size and hydrophilicity of the [Pro] anion as well as the interaction of the [Pro] anion with insulin aspart. The results also indicated that the conformational dynamics of insulin aspart were dependent on the concentration and type of ionic constituents in the IL medium. These positive observations highlight the possibility of utilizing “bio-ionic” liquids as preservation media for the formulation of protein-based products.