2.3.12. Ex Vivo Pharmacokinetic (PK) Studies

3D-printed rings were tested ex vivo in fresh porcine esophagus to determine the concentration of FTS released into the esophageal tissue overtime. These studies were performed with both pre- and post-loaded FTS-loaded rings (10 mm H, 10 mm OD, and 2 mm CS) (Supplementary Figure S5A). Drug-loaded rings were inserted into approximately 10 mm of esophageal tissue explants. The esophageal tissue explants were subsequently placed in 10 mL of PBS at 4 ◦C and incubated for 1, 3, 7, and 14 days (*n* = 3 per timepoint). At each timepoint, the rings (*n* = 3) were removed from the media and the esophageal tissue was collected and stored at −80 ◦C for pharmacokinetics analysis by LC-MS/MS. To determine the total amount of fluticasone delivered to the esophageal tissue ex vivo, fluticasone released in PBS and residual drug in the ring were quantified by HPLC analysis.
