A Standardized Ex Vivo Porcine Oromucosal Model for Evaluating Peptide Fluxes

Oromucosal administration of drugs in films, tablets, lozenges, and other dosage forms provides a convenient systemic administration route for pediatric and elderly patients, and for patients who cannot swallow capsules or tablets easily. Developing buccal and sub-lingual peptide formulations requires preclinical models that align with the non-keratinized oromucosal epithelial structures of humans, of which pigs and dogs are the most suitable. We sourced discarded fresh porcine oromucosal tissues from an abattoir. The mucosae were dissected from the underlying smooth muscle using controlled heating and then mounted in either Franz Diffusion Cells or in novel low-volume 3D-printed resin-cured inserts. Peptide-permeation enhancer combinations were added to the donor side, and permeated molecules were sampled from the receiver side and quantified by ultra-high performance liquid chromatography (uHPLC). For the inserts, transepithelial electrical resistance (TEER) values of mounted mucosae were measured using EVOM chopstick electrodes. Tissue histology was examined following incubation in both Franz diffusion cells and 3D inserts. The optimal concentration of permeation enhancer was selected when aqueous mixtures of peptide and enhancer produced an increase in permeation. Peptide permeation reached 4.3% over 3 h in three-dimensional (3D) inserts and 1.7% in Hilltop chamber models, the latter simulating direct exposure from a buccal film. Layer-by-layer polymeric mucoadhesive films containing peptide-enhancer combinations were developed and applied to mucosal tissue for permeation studies using diffusion chambers. Ex vivo peptide permeation across porcine buccal mucosae reached 2% when mucosae were exposed to the optimal combination of glycodeoxycholate (GDC) incorporated into the buccal films. These ex vivo screening studies provide a pathway to subsequent pharmacokinetic evaluation of peptide-loaded film formulations administered via the oromucosal route in pigs and people.