Characterization of critical parameters using an air-liquid interface model with RPMI 2650 cells for permeability studies of small molecules

The field of nasal drug delivery gained enormously on interest over the past decade. Performing nasal in vivo studies is expensive and time-consuming, but also unfeasible for an initial high-throughput compound and formulation screening. Therefore, the development of fast and high-throughput in vitro models to screen compounds for their permeability through the nasal epithelium and mucosa is constantly expanding. Yet, the protocols used for nasal in vitro permeability studies are varying, which limits the comparability and reproducibility of generated data. This project aimed to elucidate the influence of different culture and assay parameters of RPMI 2650 cells grown under air-liquid interface (ALI) conditions on the transepithelial electrical resistance (TEER) and apparent permeability (Papp) values of five selected reference compounds, covering the range of low to moderate to high permeability. The influence of the passage number, seeding density, and timepoint of airlift was minimal in our approach, while the substrate pore density had a significant influence on the Papp values of carbamazepine, propranolol, and metoprolol, classified as highly permeable compounds, but not on atenolol and aciclovir. Elevation of the experimental concentration of carbamazepine, propranolol, and metoprolol in the donor compartment had an increasing effect on the Papp values, while prolonging the assay time did not have a significant influence. Based on the results reported here, RPMI 2650 cells cultured under ALI conditions offer the possibility of a standardized high-throughput screening model for small molecules and their formulations for in vitro drug permeation studies to predict and select optimal conditions for their nasal delivery.