Therapeutic deep eutectic solvent based on osthole and paeonol: Preparation, characterization, and permeation behavior

Recently, a new type of drug delivery system termed therapeutic deep eutectic solvent (THEDES) was developed to increase the solubility and/or permeation ability of drugs, where an active pharmaceutical ingredient (API) was included as the component in the eutectic system. In this work, we designed a new THEDES based on two well-known active pharmaceutical ingredients (APIs), osthole and paeonol. The macroscopic properties and the microscopic structures were investigated by various techniques. The THEDES has been proven to retain the bioactivities of pure APIs and shows better solubility than pure APIs in water. Furthermore, an O/W microemulsion formulation was constructed with THEDES as the oil phase and TX-100 and 1,2-propanediol serving as the surfactant and the co-surfactant respectively, which showed good stability and an average size of 50 nm. The permeation behavior of the THEDES was compared to that of pure APIs in gel form, and the results suggested that the THEDES had a better permeation ability than pure APIs at the same concentrations. Hence, a multifunctional drug delivery system with great simplicity and convenience was demonstrated herein, showing great potential application in the transdermal delivery systems.