A perfusion bioreactor platform for dynamic cell-based permeability studies: Design and modeling

Permeability is a critical parameter governing transport across physiological barriers. It is commonly evaluated using static in vitro assays that rely on early time approximations and neglect system-level transport effects, limiting the interpretation of permeability data from such systems. In this work, a new in vitro platform was developed that integrates fluid flow with a standard cell culture plate and an indwelling membrane insert to enable automated time-resolved permeability measurements. Tracer experiments using FITC-dextran were conducted to characterize transport behavior within the system across multiple flow rates. A transport model was developed using general mass balance principles across apical and basal compartments and extended to incorporate a residence time distribution framework using an “N-CSTR tanks in series” model. Model predictions were evaluated against experimentally collected fraction-averaged data to ensure consistency with the sample collection process. Control experiments demonstrated that when membrane resistance is negligible, the observed early-stage concentration dynamics are dominated by dispersion requiring explicit residence-time modelling. In contrast, permeability estimates for a skin epithelium operated near unity Peclet number were robust to dispersion, indicating a permeability-limited transport. Together, these findings highlight the importance of and guide system-aware modelling for interpreting dynamic in vitro permeability measurements.