Enhancing the Solubility and Transdermal Delivery of Drugs Using Ionic Liquid-In-Oil Microemulsions

The development of hydrophobic drug and protein delivery carriers remains a challenge. To synthesize L-(-)-carnitine-based ionic liquid (IL), this study applies the density functional theory to investigate the hydrogen bonds and van der Waals force that govern L-(-)-carnitine-based IL formation. An ionic liquid-in-oil microemulsion (IL/O ME) is then developed to facilitate the transdermal delivery of proteins and increase the solubility of drugs. IL/O ME is prepared using isopropyl myristate (IPM), Tween 80/Span 20, and L-(-)-carnitine-based IL. The skin permeation studies conducted using mouse skin show that the insulin permeation percentage of the developed IL/O ME is 3.55 folds higher than that of phosphate-buffered saline and 2.91 folds better than that of a hydrophilic L-(-)-carnitine-based IL. In addition, the solubility of two drug molecules, that is, rosiglitazone and bezafibrate, in IL/O ME is at least 49.28 folds higher than their solubility in water or IPM. Therefore, IL/O ME can significantly improve the solubility of drugs and increase the permeability of proteins (e.g., insulin), thus demonstrating a promising potential as a delivery carrier.