Biological Barriers: Transdermal, Oral, Mucosal, Blood Brain Barrier, and the Blood Eye Barrier

© Springer Science+Business Media New York 2013. And Gregor Cevc 2013. All rights reserved. Compartmentalisation is a precondition for the development of life, allowing concentration gradients to be maintained, facilitating selective transport of molecules, functional polarisation, protection of cells and tissues. Consequently, organisms have evolved highly sophisticated structures and mechanisms that allow compartmentalisation to be maintained and controlled in a highly regulated fashion. Under normal conditions these compartmentalising structures are essential building blocks of life, their smooth functioning being central to our health. However, the same effectiveness that is a bonus under physiological conditions means the same structures may become considerable barriers to the pharmacotherapy of diseases, as access of drugs to the sites of disease may be severely restricted. This chapter describes the architecture, organisation, and function of key barriers that therapeutic nanoparticles may encounter for the most important routes of drug administration. The epithelial barriers (skin, mucosa of the airways, and gastrointestinal tract) and endothelial barriers share many commonalities as they all share key design elements that have evolved to support compartmentalisation