Bigels as drug delivery systems: From their components to their applications

•Bigels are systems that usually result from mixing a hydrogel and an organogel.•A hydrophilic biopolymer is commonly the structuring agent of the aqueous phase.•An organogelator causes the vegetable oil to be gelled forming the organogel.•Factors like organogel/hydrogel ratio condition bigels features and drug release.•Bigels for transdermal, buccal and vaginal drug delivery have been developed.