In vitro demonstration of intestinal absorption mechanisms of different sugars using 3D organotypic tissues in a fluidic device

Theoretical and Computational Fluid Dynamics (CFD) analysis Firstly, a theoretical model was developed starting from the geometry of the MIVO® device to calculate the flow rate to set in the peristaltic pump for obtaining a capillary velocity beneath the EpiIntestinal tissue model. The 3D domain, the related size and dimensions were calculated based on the real dimensions of the circuit used during the tests. Successively, after reproducing the geometry through a commercial software, the fluid dynamics within the MIVO® chamber were modelled by using the Laminar Fluid Flow module of Comsol Multiphysics 5.3a. The fluid was assumed to be laminar and incompressible, and the fluid profile was based on Navier-Stokes equations (1a, 1b):


In vitro demonstration of intestinal absorption mechanisms of different sugars using 3D organotypic tissues in a fluidic device Supplementary Data 1 Theoretical and Computational Fluid Dynamics (CFD) analysis
Firstly, a theoretical model was developed starting from the geometry of the MIVO® device to calculate the flow rate to set in the peristaltic pump for obtaining a capillary velocity beneath the EpiIntestinal tissue model. The 3D domain, the related size and dimensions were calculated based on the real dimensions of the circuit used during the tests.
Successively, after reproducing the geometry through a commercial software, the fluid dynamics within the MIVO® chamber were modelled by using the Laminar Fluid Flow module of Comsol Multiphysics 5.3a. The fluid was assumed to be laminar and incompressible, and the fluid profile was based on Navier-Stokes equations (1a, 1b): where is the fluid velocity and the fluid pressure across the system. The density  and dynamic viscosity  values were approximated with those of water.

FE-SEM analysis on EpiIntestinal tissue model after lactulose absorption test
As shown in Fig. S5, sugar crystals remain deposited over the surface of the villi present in the EpiIntestinal tissue model.

Fig. S3: FE-SEM analysis of intestinal tissue after lactulose absorption test within MIVO chamber showing an intestinal villus
Bar is 1 µm.

Sugar absorption test in static conditions
Sugar absorption tests were repeated in static conditions. As shown in Figure S3 the percentage of absorbed mannitol was much greater than that of lactulose for each time point, as in dynamic conditions. Although a slight reduction of the amount of lactulose passed in static conditions can be observed, a statistical analysis between the amount of both sugars passed in static and dynamic conditions showed no significant differences for each experimental time point (*p>0.05).

Lactulose absorption test at a lower concentration
Sugar absorption tests were repeated in dynamic conditions with a lower lactulose concentration in the donor chamber (33.3 mg/ml). As shown in Fig. S4, the percentage of sugar absorbed is around 1%, consistent with the values obtained with the other concentration tested (55.5 mg/ml and 44.4 mg/ml). This confirms that the amount of sugar passed is not dose-dependent, differently from mannitol.

Drug permeation tests
To confirm that the permeability of compounds in the 3D intestinal tissue model correlates with that of historical human absorption, we used four model drugs representing either low (≤ 60%) or high (≥80%) absorption in humans. The samples of donor and receiver side transport buffers from the permeability experiments using healthy and untreated 3D intestinal tissues were analyzed using LC/MS/MS as described previously (Ayehunie et al 2018). The apparent permeability coefficient (Papp) was calculated according to the equation: