The Colonic-PVPA: a new application of the Phospholipid Vesicle-based Permeation Assay (PVPA) as a mucus-comprising cell-free in vitro model for mucosal colonic drug delivery.

Colonic drug delivery has gained increasing attention as a treatment approach for both local and systemic therapy. However, the colonic mucus layer can greatly influence a drug's fate by acting as a selective barrier, facilitating the filtration or trapping of drug molecules and carriers based on size and molecular interactions. Therefore, a simple in vitro permeability model that mimics the colonic mucus layer is essential for predicting how a drug behaves in the colon in drug development. Building on the well-established, easy-to-use, cost-effective, and cell-free in vitro model Phospholipid Vesicle-based Permeation Assay (PVPA), the Colonic-PVPA was developed by incorporating the Porcine Artificial Colonic Mucus (PACM). After verifying the barrier's integrity in the presence of the PACM, the impact of biosimilar mucus on drug permeation was investigated using six model drugs and compared to the previous generation of PVPA in the absence and presence of hydrated mucins (Mucus-PVPA). The Colonic-PVPA successfully distinguished compounds from different BCS classes and with physicochemical properties, while hindering their permeation across the barrier due to the presence of the biosimilar mucus. Additionally, the interaction between the mucus layer and mucointeracting formulations has been assessed through the Colonic-PVPA, confirming the model's usefulness in formulation development of mucoadhesive (chitosan-coated) and mucopenetrating (PEGylated) nanoparticles. In all cases, significant differences between Mucus-PVPA and Colonic-PVPA were observed, highlighting the importance of mucus composition in drug permeation. Overall, the Colonic-PVPA proves to be a promising in vitro model that resembles the colonic environment, making it suitable for drug permeability screening and formulation development.