Fig. 6

Engineered biological barrier models involving semipermeable membranes or microchannels. a A gut-on-a-chip microfluidic device with spontaneously formation of villi resulting from mechanical cues [107]. TEER profile shows intestinal barrier injury in the presence of pathogenic bacteria (EIEP) or immune cells plus either non-pathogenic bacteria (GFP-EC) or lipopolysaccharide (LPS) endotoxin. b A human kidney proximal tubule-on-a-chip. Immunofluorescence images and bar plots shows increased cell height and increased expression of the tight junction protein ZO-1, aquaporin 1 (AQP1; green), Na/K-ATPase (magenta), and primary cilia in epithelial cells under flow conditions. Adapted from [109] with permission from The Royal Society of Chemistry. c Microfluidic platform for the development of human skin equivalents. Histological and immunofluorescence images demonstrate an improved epidermal morphogenesis and dermoepidermal junction when the tissue is maintained in a dynamic air-liquid interface. Adapted from [110] with permission from Elsevier. d Neonatal BBB model consisted of side-by-side chambers connected through microchannels [114]. Immunofluorescence image shows direct contact communication between endothelial cells (ZO-1; green) and astrocytes (astrocytic marker GFAP; red). e Microfluidic model of the BRB where cells are arranged in parallel compartments and interconnected through a grid of microgrooves [10] – Adapted by permission of The Royal Society of Chemistry. TEER measurement during a calcium switch procedure is performed with two electrodes in the basal side instead of in the apical and basal sides. f Scalable liver-on-a-chip microdevice for long-term maintenance of hepatocyte function in vitro, in which microchannels artificially mimic the fenestrated endothelial cells of the liver [115] (Copyright IOP Publishing. Reproduced with permission. All rights reserved)