Microfluidic method for measuring endothelial permeability

Wong, Jeremy 1, 3; Young, Edmond 1, 2; Simmons, Craig 1, 2, 3

1. Institute of Biomaterials and Biomedical Engineering; 
2. Department of Mechanical and Industrial Engineering; 
3. Translational Biology and Engineering Program

The endothelium is a semipermeable barrier that regulates transport of molecules between blood and tissue. Endothelial permeability is an important metric of vascular barrier function in the study of various pathophysiological processes and drug development. Permeability to solutes is most commonly assessed in vitro by monitoring the diffusive transport of fluorescently-labelled tracer molecules across an endothelial cell monolayer using Boyden chambers. Recently, microfluidic methods for permeability assessment have incorporated flow-induced shear stress, an important biomechanical force in the vascular microenvironment. These methods, however, rely on the use of costly, complex and bulky optical instrumentation, limiting assay throughput. In this work, we present a novel microfluidic method for the electrochemical determination of permeability with simultaneous application of shear stress. Permeability-dependent transport of an electroactive tracer molecule in a bilayer microfluidic device was monitored in real-time using an integrated electrochemical cell, significantly reducing instrumentation footprint and complexity. Permeability values were then extracted from these measurements using a computational model of mass transport in the device. In order to validate the method, the permeability of cell-free porous membrane supports was determined under static and shear flow conditions. Good agreement was found between theoretical and experimental results for all conditions. This method will be extended to determine the endothelial permeability of cell-laden membranes.