Porcine buccal mucosa as in vitro model: effect of biological and experimental variables

Porcine buccal mucosa has been used as an in vitro model to assess the potential of delivering a molecule via the transbuccal route. However, permeation studies across porcine buccal mucosa show high variability due to various experimental and biological factors. The variability associated with the use of different mucosal regions, tissue storage conditions and tissue processing methods on drug permeation was investigated in this study. The permeability of model diffusants was significantly higher in the region behind the lip when compared to the cheek region because the latter has a thicker epithelium. Porcine buccal mucosa retained its integrity in Kreb's bicarbonate ringer solution at 4 degrees C for 24 h while many other storage conditions resulted in loss of epithelial integrity. Separation of the epithelium from underlying connective tissue either surgically or by heat treatment resulted in an epithelial thickness of approximately 150 microm. Separation of epithelium from the underlying connective tissue by heat treatment did not adversely affect its permeability and integrity characteristics. Investigation of these important biological and experimental variables provides guidance for conducting in vitro transbuccal permeation studies.