A Microfluidic Barrier-on-Chip Platform with Integrated Porous Membrane Cell-Substrate Impedance Spectroscopy

Organ-on-chip (OOC) systems that recapitulate microenvironmental features like coculture, fluid shear stress, and extracellular matrix are useful for modeling biological barriers. OOC barrier integrity measurements are often done by trans-endothelial/epithelial electrical resistance (TEER) measurement, but this approach is confounded by nonuniform current distribution and interference from biomaterials typical to such systems. We addressed this gap by incorporating gold leaf porous membrane electrical cell-substrate impedance sensing (PM-ECIS) electrodes (diameters of 250, 500, or 750 μm) into a biocompatible tape-based barrier-on-chip (BOC) platform. PM-ECIS measurements were robust to fluid shear (5 dyn/cm²) in cell-free devices, yet highly sensitive to flow-induced changes in an endothelial barrier model. Perfusion (0.06 dyn/cm²) corresponded to significant decreases in impedance at 40 kHz (p < 0.01 for 750, 500 μm electrodes) and resistance at 4 kHz (p < 0.05 for all electrode sizes) relative to static control, with minimum values reached 6.5-9.5 h after flow induction. We also demonstrated that PM-ECIS is robust to the presence of hydrogel, and unlike chopstick TEER, has the measurement sensitivity to detect human brain microvascular endothelial monolayers in a hydrogel coculture model. The sensitive, noninvasive, real-time measurements of barrier function in microfluidic PM-ECIS setups makes it well-suited for OOC applications that include features like 3D coculture, biomaterials, and shear stress.