Overview of a 10-chamber in vitro model. Overview of our 10-chamber in vitro model based on a simplified three-chamber system using gravity-driven flow . (A) Prototype unit on a rocker platform. (B) Close-up inverted view of the prototype unit after a dye distribution study. (C) Exploded schematic showing the compartmentalization design for a 10-chamber system within this single unit. Barrier tissues (for example, gastrointestinal (GI) tract, skin, and so forth) are made by plating cells and allowing them to grow into a layer on a pretreated polycarbonate membrane (0.4 μm pore size) that was sandwiched between a chamber gasket and another gasket or a polycarbonate channel plate creating chambers for the cells. The design provides an apical and a basolateral side for each chamber, allowing passage of chemicals across the barrier. Nonbarrier tissues are three-dimensional constructs made by resuspending cells in hydrogels or plating them on a polymeric scaffold. The three-dimensional tissue constructs are placed directly onto a polycarbonate membrane that is again sandwiched between a chamber gasket and another gasket or polycarbonate channel plate creating the chambers for the cells.