Graphs showing nicotine levels measured over time by MS within the apical and basal channels of the linked Gut, Liver and Kidney Chips, as well as in the AV Reservoir, when nicotine was continuously infused through the lumen of the Gut chip at a dose of 396±16 μM for 84 hrs followed by a 56 hrs wash-out period (white bars) compared with predictions of the computational DMPK model (black bars). Values are also shown for the nicotine breakdown product, cotinine, in samples from the effluent of the epithelial channel of the Liver Chip (data are pooled from 3 separated experiments; error bars indicate standard deviation).