Advances and future perspectives in epithelial drug delivery

Epithelial surfaces protect exposed tissues in the body against intrusion of foreign materials, including xenobiotics, pollen and microbiota. The relative permeability of the various epithelia reflects their extent of exposure to the external environment and is in the ranking: intestinal = nasal > bronchial > tracheal > vaginal > rectal > blood-perilymph barrier (otic), corneal > buccal > skin. Each epithelium also varies in their morphology, biochemistry, physiology, immunology and external fluid in line with their function. Each epithelium is also used as drug delivery sites to treat local conditions and, in some cases, for systemic delivery. The associated delivery systems have had to evolve to enable the delivery of larger drugs and biologicals, such as peptides, proteins, antibodies and biologicals and now include a range of physical, chemical, electrical, light, sound and other enhancement technologies. In addition, the quality-by-design approach to product regulation and the growth of generic products have also fostered advancement in epithelial drug delivery systems.(c) 2022 Elsevier B.V. All rights reserved.

Automated summary

Epithelial surfaces play a crucial role in protecting the body from foreign materials and can be utilized for drug delivery. The permeability of different epithelia varies based on their exposure and function. Advancements in epithelial drug delivery systems have been driven by quality-by-design approach and the growth of generic products.