Cmtpx dye

The Escherichia coli strain (11775, ATCC) was purchased from China General Microbiological Culture Collection Center (CGMCC). It was cultivated in autoclaved LB medium at 37°C and 200 rpm for 12 h. After bacterial cell density was adjusted to ∼1.0 × 10⁷ CFU/mL, E. coli was spun down (10,000 g, 8 min), and resuspended in antibiotics-free DMEM medium with 5 μmol/mL red cell-tracker (CMTPX Dye, Invitrogen), and cultivated at 37°C for 30 min. Then E. coli was spun down, and resuspended in antibiotics-free DMEM + 10 FBS medium immediately and flowed into the intermediate microchannel containing the villus epithelium pre-cultivated in the microfluidic chip with peristalsis plus vascular endothelial cell for 4 days. At the same time, macrophages (4 × 10⁵ cells/mL) were introduced into the vascular lumen. After E. coli cells and macrophages cells were allowed to attach to the surface of epithelium or endothelium during ∼2 h under static condition, fresh antibiotics-free culture medium was perfused into all three microchannels at 60 μL/h with cyclic peristalsis (15%, 0.15 Hz).