Mucosal drug delivery: barriers, in vitro models and formulation strategies

Abstract

Delivery of prophylactic and therapeutic drugs via administration to the mucosal sites of the body may be advantageous for several reasons. However, for peptide and protein drugs being highly charged, bulky and hydrophilic, it may be challenging to cross the mucosal barrier and reach their target site locally in the underlying tissue or after absorption to the systemic circulation. Thus, emerging drug formulation technologies explore a variety of strategies to improve the interaction with both the viscous mucus matrix surface lining the epithelial barrier as well as with the epithelium. However, representative in vitro and in vivo models are needed for the assessment of the delivery potential of such novel delivery systems, e.g. nanoparticles, and for elucidating the detailed mechanisms related to the delivery enhancement. This review focuses on the impact of the mucus layer on mucosal delivery, reviews the state-of-the-art cell culture in vitro models used, and the formulation strategies applied to improve mucosal drug delivery.