Figure 1. The HuMiX model.

(a) Conceptual diagram of the HuMiX model for the representative co-culture of human epithelial cells with gastrointestinal microbiota. (b) Annotated exploded view of the HuMiX device. The device is composed of a modular stacked assembly of elastomeric gaskets (thickness: 700 μm) sandwiched between two polycarbonate (PC) enclosures, and each gasket defines a distinct spiral-shaped microchannel with the following characteristics: length of 200 mm, width of 4 mm and height of 0.5 mm, amounting to a total volume of 400 μl per channel. Semi-permeable membranes affixed to the elastomeric gaskets demarcate the channels. The pore sizes of the membranes were chosen for their intended functionality. A microporous membrane (pore diameter of 1 μm), which allows diffusion-dominant perfusion to the human cells, is used to partition the perfusion and human microchambers. A nanoporous membrane (pore diameter of 50 nm) partitions the human and microbial microchambers to prevent the infiltration of microorganisms, including viruses, into the human microchamber. (c) Photograph of the assembled HuMiX device (scale bar, 1 cm). (d) Diagram of the experimental set-up of the HuMiX model with provisions for the perfusion of dedicated oxic and anoxic culture media as well as the monitoring of the oxygen concentration and transepithelial electrical resistance. The oxygen concentration in the anoxic medium is maintained at 0.1% by continuously bubbling the medium with dinitrogen gas. (e) Diagrammatic overview of the HuMiX co-culture protocol.