Permeability across a novel microfluidic blood-tumor barrier model

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Background: The lack of translatable in vitro blood-tumor barrier (BTB) models creates challenges in the develop‑ ment of drugs to treat tumors of the CNS and our understanding of how the vascular changes at the BBB in the pres‑ ence of a tumor. Methods: In this study, we characterize a novel microfluidic model of the BTB (and BBB model as a reference) that incorporates flow and induces shear stress on endothelial cells. Cell lines utilized include human umbilical vein endothelial cells co-cultured with CTX-TNA2 rat astrocytes (BBB) or Met-1 metastatic murine breast cancer cells (BTB). Cells were capable of communicating across microfluidic compartments via a porous interface. We characterized the device by comparing permeability of three passive permeability markers and one marker subject to efflux. Results: The permeability of Sulforhodamine 101 was significantly (p < 0.05) higher in the BTB model (13.1 ± 1.3 × 10−3 , n = 4) than the BBB model (2.5 ± 0.3 × 10−3 , n = 6). Similar permeability increases were observed in the BTB model for molecules ranging from 600 Da to 60 kDa. The function of P-gp was intact in both models and consistent with recent published in vivo data. Specifically, the rate of permeability of Rhodamine 123 across the BBB model (0.6 ± 0.1 × 10−3 , n = 4), increased 14-fold in the presence of the P-gp inhibitor verapamil (14.7 ± 7.5 × 10−3 , n = 3) and eightfold with the addition of Cyclosporine A (8.8 ± 1.8 × 10−3 , n = 3). Similar values were noted in the BTB model. Conclusions: The dynamic microfluidic in vitro BTB model is a novel commercially available model that incorporates shear stress, and has permeability and efflux properties that are similar to in vivo data.