Interest so far has been on exploring biological barriers of the gastrointestinal tract and the skin, while developing suitable drug delivery carriers (nanoparticles, microparticles, nanostructured lipid carriers (NLC) as well as mucoadhesive system) capable of delivering actives to target sites through epithelial barriers. These delivery systems are normally designed to have high drug payload but with controllable drug release for extended periods of time from biodegradable materials.