Mucus-penetrating phage-displayed peptides for improved transport across a mucus-like model.

The objective of this work is to use phage display libraries as a screening tool to identify peptides that facilitate transport across the mucus barrier. Mucus is a complex selective barrier to particles and molecules, limiting penetration to the epithelial surface of mucosal tissues. In mucus-associated diseases such as cystic fibrosis (CF), mucus has increased viscoelasticity and a higher concentration of covalent and non-covalent physical entanglements compared to healthy tissues, which greatly hinders permeability and transport of drugs and particles across the mucosae for therapeutic delivery. Treatment of CF lung diseases and associated infections must overcome this abnormal mucosal barrier. Critical bottlenecks hindering effective drug penetration remain and while recent studies have shown hydrophilic, net-neutral charge polymers can improve the transport of nanoparticles and minimize interactions with mucus, there is a dearth of alternative carriers available. We hypothesized that the screening of a phage peptide library against a CF mucus model would lead to the identification of phage-displayed peptide sequences able to improve transport in mucus. These combinatorial libraries possess a large diversity of peptide-based formulations (108-109) to achieve unprecedented screening for potential mucus-penetrating peptides. Here, phage clones displaying discovered peptides were shown to have up to 2.6-fold enhanced diffusivity in the CF mucus model. In addition, we demonstrate reduced binding affinities to mucin compared to wild-type control. These findings suggest that phage display libraries can be used as a strategy to improve transmucosal delivery.