Liquid formulations based on ionic liquids in biomedicine

Ionic liquids (ILs) are innovative ionic solvents with unique properties of negligible vapor pressure, favorable conductivity, high thermal and chemical stability as well as self-assembly capability. These characteristics make ILs great potentials for biomedical applications. ILs may serve as the surfactant, the aqueous phase and the oil phase in liquid formulations, which result in tailoring the structures and functionalities of the liquid formulations to fulfil specific application scenarios. This review discusses the state-of-the-art progresses for the four types of ionic liquid-based liquid formulations, i.e., ionic liquid-based microemulsions, ionic liquid-based micelles, ionic liquid-based vesicles, and ionic liquid solvents. Special emphasis is focused on the recent applications of these liquid formulations in biomedical fields, in terms of improving the solubility and stability of the drugs, enhancing transdermal delivery, and stimulus-responsive drug release performance.