Natural deep eutectic solvents as a storage medium for human interferon-α2: a green and improved strategy for room-temperature biologics

The inherent vulnerability of protein biologics to high temperature is the origin of their limited use in clinical settings where proper storage and handling systems are not available. Herein, we demonstrate the first application of natural deep eutectic solvents (NADES) as a temperature-stable storage medium for a real therapeutic protein, human interferon-alpha 2 (IFN-α2). A formulation of IFN-α2 based on a NADES composed of choline chloride and fructose at a 1:1 molar ratio (CCl:Fru) had no influence on the activity of IFN-α2. The NADES provided an appropriate environment for effective protection of IFN-α2 from thermal denaturation at mid (37 °C) and high (70 °C) temperatures during long-term (90 days) and short-term (2 h) storage. Protein stability in the presence of CCl:Fru was demonstrated by orthogonal or complementary methods, including in vitro activity assay, circular dichroism spectroscopy and extrinsic fluorescence spectroscopy. In view of their biocompatibility, customizable properties, and the simplicity of synthesis and use, NADESs are suggested as a green and improved short-term and long-term storage medium that could facilitate the development of room-temperature biologics.