3D Printed Transwell Microfluidic Devices for Epithelial Cell Culture with Shear Stress.

In this paper, we describe how 3D printing can be used to fabricate a microfluidic-based transwell cell culture system with robust fluidic connections for long-term cell culture and recirculating flow. This approach consists of an electrospun collagen scaffold sandwiched between two laser-cut Teflon membranes that match the fluidic design. Madin-Darby canine kidney (MDCK) cells were cultured on the collagen scaffold to create an epithelial cell monolayer. Introduction of cells into the device was facilitated by a printed reservoir that could be closed after proper cell seeding with minimal effect of the flow profile over the cells. The resulting MDCK cell monolayer was exposed to continuous flow and transport through the cell layer and could be monitored by sampling from the basolateral channel network. COMSOL simulations and flow injection analysis were used to determine the effect of the reservoir geometry on the shear stress that cells experience. A variety of analytical tools were used to assess the effect of flow over the cells in this model. This includes confocal microscopy and potentiometric scanning ion conductance microscopy (to determine morphology and conductance), as well as transendothelial/epithelial electrical resistance (TEER) measurements and reverse transcription-quantitative polymerase chain reaction studies (for gene expression analysis). Finally, a drug transport study with the cell model was carried out using two drugs (caffeine and digoxin) to determine the apparent permeability of high and low permeability drugs, with results being similar to findings from in vivo studies as well as studies where MDCKs have been transfected to form more resistive barriers. This approach holds great promise for the creation of more in vivo-like, flow-based barrier models for transport studies.