Development of a microfluidic device to observe dynamic flow around the villi generated by deformation of small...

The mucosal immune system in the small intestine is crucial for human health. For the immune response, mutual contact between gut bacteria and intestinal epithelial cells is important because there are unique epithelial cells specialized in gut bacteria sampling on the villi. The travel of gut bacteria to the villi is led by a complex dynamic flow in the small intestine. However, the complex dynamic flow around the villi has not yet been explored at a micro scale. In this study, we proposed a microfluidic device to observe the flow around the villi generated by the dynamic deformation of small intestinal tissue. The microfluidic device had 3 pneumatic actuators to drive small intestinal tissue. The pneumatic actuator with small intestinal tissue achieved a sufficient stroke of 1000 mm and reproducibility. A mouse's immotile small intestinal tissue was driven by the pneumatic actuator, resulting in dynamic flow; the villi dynamics can be explored. The dynamic flow of the villi is observed using 1 μm fluorescent microbeads as markers. Dynamic flow in the small intestinal tissue is classified into three modes based on the bead speed. Among these modes, in transitional flow, the microbeads slow down around the villi, resulting in an increased probability of microbead and villi adhesion. Two further unique flow behaviors are as follows: the fluorescent microbeads float and remain within the gaps of villi under the dynamic deformation of the small intestinal tissue, and a stirring flow occurs in the dent of the small intestinal tissue.