Organogels and their use in drug delivery — A review

Organogels are semi-solid systems, in which an organic liquid phase is immobilized by a three-dimensional network composed of self-assembled, intertwined gelator fibers. Despite their majoritarily liquid composition, these systems demonstrate the appearance and rheological behaviour of solids. Investigative research pertaining to these systems has only picked up speed in the last few decades. Consequently, many burning questions regarding organogel systems, such as the specific molecular requirements guaranteeing gelation, still await definite answers. Nonetheless, the application of different organogel systems to various areas of interest has been quick to follow their discoveries. Unfortunately, their use in drug delivery is still quite limited by the scarce toxicology information available on organogelators, as well as by the few pharmaceutically-accepted solvents used in gel systems. This review aims at providing a global view of organogels, with special emphasis on the interplay between the gelator's structural characteristics and the ensuing intermolecular interactions. A subsequent focus is placed on the application of organogels as drug delivery platforms for active agent administration via diverse routes such as transdermal, oral, and parenteral.