Figure 1. Schematic of Transwell assay for measuring Tenofovir transport into and through an excised tissue specimen.

Circular porcine buccal tissue specimens were maintained in Transwell supports, under which was a bath of PBS to hydrate the tissue. Matrigel was used to create a gelatinous seal around tissue edges to prevent leakage. An isotonic solution of 1% Tenofovir in PBS was applied to the apical surface. The assay was maintained at 37°C and 5% CO₂ in a Heracell incubator for 30 min to 6 h.