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Updated: Aug 7, 2026
Models and Methods to Evaluate Transport of Drug Delivery Systems Across Cellular Barriers
Published on: October 17, 2013
A novel tool to characterize paracellular transport: the APTS-dextran ladder
Winfried Neuhaus1, Elisabeth Bogner, Michael Wirth
1Department of Medicinal Chemistry, University of Vienna, Pharmacy Center, Althanstrasse 14, A-1090, Vienna, Austria.
Purpose:
The aim of this work was to develop an easy, manageable, and precise analytic tool to describe the tightness of cell layers by a molecular weight ladder.
Methods:
Dextrans were labeled by reductive amination with fluorescent 8-aminopyrene-1,3,6-trisulfonate (APTS). This mixture, including the internal standard diazepam, was used for transport studies in Transwell models using Caco-2, ECV304, and PBMEC/C1-2 cell lines. Samples were analyzed by fluorimetry, capillary electrophoresis, and reverse-phase high-performance liquid chromatography.
Results:
Following this approach, a logarithm correlation of R2 = 0.8958 between transepithelial electrical resistance (TEER) and APTS-dextran permeability was shown. In addition, a TEER-dependent permeability pattern could be observed including each single fraction from free APTS, APTS-glucose up to APTS-dextran consisting of 35 glucose units. The TEER-independent permeability coefficients of diazepam and confocal laser scanning microscopy images confirmed the paracellular transport of APTS-dextran.
Conclusions:
All in all, the developed APTS-dextran ladder is a useful tool to characterize cell layer tightness and especially to describe paracellular transport ways and the extent of leakiness of cell layers (for blood-brain barrier or intestinal studies) over time--applying a wide array from smaller to larger molecules at the same time to refine TEER, sucrose, or Evans blue measurements.
