I-TEP: A Simple and Affordable Method to Measure Permeability in Reconstructed Tissues Combined with DAMO-TSC-Based...

Trans-epithelial permeability is a critical functional parameter for reconstructed tissues, particularly in genitourinary tissue engineering, where urine leakage must be avoided. Although Franz diffusion cells are considered the gold standard for permeability measurements, their cost and limited accessibility restrict their widespread use. In parallel, the reliable quantification of urea in culture media remains challenging due to protein interference and assay cost. The Inexpensive Trans-Epithelial Permeability (I-TEP) test is a simple and a low-cost Franz-like permeability system which can be combined with an optimized diacetyl monoxime-thiosemicarbazide (DAMO-TSC) colorimetric urea assay. I-TEP system relies on readily available laboratory components to create physically separate donor and receiver compartments, with the tissue acting as the sole diffusion interface. The DAMO-TSC assay was optimized through systematic evaluation of deproteinization, incubation time, storage conditions, and serum interference. The I-TEP test showed a strong correlation with conventional Franz diffusion cells when testing similar tissue samples. Deproteinization was identified as a mandatory step for accurate urea quantification in serum-containing media. The combined approach was successfully applied on engineered genitourinary tissues, demonstrating sensitivity to tissue maturation and cellular composition. This protocol provides a proof of concept for an affordable, robust, and autonomous method for routine permeability assessment, bridging the gap between costly commercial systems and high-throughput experimental needs.