Transport regimes in microfluidic bioreactors: hepatocyte culture as a case study

Microflow reactors provide an ideal environment for the artificial growth of biological tissues, since temperature and concentration of the chemical species can be accurately controlled. In this work, we present an analysis of transport regimes and mechanisms underlying the cell activity in the microenvironment, in terms of reaction rates, product and reactants spatio-temporal profiles. We set up an advection-diffusion-reaction transport model to reproduce an hepatic sinusoide, to a design guidance for the experimental prototype. The device consists of a U-shape sinusoid equipped with a microfluidic barrier, simulating endotelial cells, which separes the inflow-outflow channel for oxigen and nutrients uptake from internal chamber hosting hepatic cells. Due to the small scale, creeping flow conditions prevail, and the focus of the analysis to investigate the transport of oxygen and nutrients from the laminar streams crossing the device to the immobilized cell phase. Assuming a nonlinear (Michaelis-Menten) kinetics of consumption of the transported species in the bulk cell phase, a wide variety of flow rate conditions are considered, as well as values of the bare molecular diffusivity of the transported species, ranging in an interval of four decades. In the specific scale and geometry, the impact of flowrate conditions on the concentration field is strongly dependent on the diffusivity of target chemical species.