A new microphysiological platform to study the permeation of neuroactive agents across intestinal and brain barriers.

To replicate key physiological barriers in vitro, we utilized the CELLBLOKS® modular microphysiological system. Specifically, human cerebral microvascular endothelial hCMEC/D3 cells, human retinal pigment epithelial (HRPE) cells, and rat small intestinal IEC-6 cells were grown in CELLBLOKS® to mimic the blood-brain (BBB), blood-cerebrospinal fluid (BCSFB), and intestinal (IB) barriers, respectively. Eugenol is an essential oil component known to permeate the central nervous system (CNS) in vivo after intravenous and oral administrations; it was therefore used for simulated intravenous and oral administrations into the CELLBLOKS® system, using also celiprolol as negative control compound, since it is known for its poor ability to permeate in the CNS from the bloodstream. In particular, the intravenous administration (systemic) of the compounds was simulated by their direct addition to the bloodstream-like lower channel of CELLBLOKS® (basolateral side of both CSFB and IB; apical side for BBB), whereas their oral administration was simulated by apical addition to IEC-6. Permeation measurements, via HPLC, across physiological barriers cultured in CELLBLOKS® demonstrated that, following both simulated oral and systemic administration, eugenol crosses the mimicked BBB and the BCSFB indiscriminately; conversely, the permeation of celiprolol across these barriers results strongly limited in comparison to eugenol. To assess downstream neuroactivity, dopaminergic neuron-like PC12 cells were cultured on NANOSTACKS™ inserts and incorporated into the BBB and BCSFB blocks. After simulated intravenous and oral administrations, significant eugenol-induced dopamine release by PC12 cells was evidenced both in BBB- and BCSFB-delimited neuronal-like compartments. These results validate the CELLBLOKS® and NANOSTACKS™ platforms as robust tools characterized by low costs, high reproducibility and ease of manipulation for in vitro studies of brain targeting of new drugs. This system requires two weeks culture period to be ready for the simulation in vitro of IB, BBB, BCFSB and neuronal tissues, appearing useful in limiting pre-clinical animal testing.