Ionic Liquids for Enhanced Drug Delivery: Recent Progress and Prevailing Challenges.

Ionic liquids (ILs) are a class of nonmolecular compounds composed only of ions. Compared with traditional organic solvents, ILs have the advantages of wide chemical space, diverse and flexible structures, negligible vapor pressure, and high thermal stability, which make them widely used in many fields of modern science, such as chemical synthesis and catalytic decomposition, electrochemistry, biomass conversion, and biotransformation biotechnology. Because of their special characteristics, ILs have been favored in the pharmaceutical field recently, especially for the development of efficient drug delivery systems. So far, ILs have been successfully designed to promote the dissolution of poorly soluble drugs and the destruction of physiological barriers, such as the tight junction between the stratum corneum and the intestinal epithelium. In addition, ILs can also be combined with other drug strategies to stabilize the structure of small molecules. This Review mainly introduces the application of ILs in drug delivery, emphasizes the potential mechanism of ILs, and presents the key research directions of ILs in the future.