Gravity-driven microfluidic device placed on a slow-tilting table enables constant unidirectional perfusion culture of human induced pluripotent stem cells

Gravity-driven microfluidics, which utilizes gravity force to drive liquid flow, offers portability and multi-condition setting flexibility because they do not require pumps or connection tubes to drive the flow. However, because the flow rate decreases with time in gravity-driven microfluidics, it is not suitable for stem cell experiments, which require long-term (at least a day) stability. In this study, gravity-driven microfluidics and a slow-tilting table were developed to culture cells under constant unidirectional perfusion. The microfluidic device was placed on a slow-tilting table, which tilts unidirectionally at a rate of approximately 7° per day to compensate for the reduction in the flow rate. Computational simulations showed that the pulsation of the flow arising from the stepwise movement of the table was less than 0.2%, and the flow was laminar. Hydrophilization of the tanks increased the flow rate, which is consistent with the theoretical values. We showed that vitronectin is better than laminin 511 fragments as a coating material for adhering human induced pluripotent stem cells on a microchamber made of polydimethylsiloxane, and succeeded in culturing the cells for 3 days. It is believed that the system offers easy-to-use cell culture tools, such as conventional multiwell culture vessels, and enables the control of the cell microenvironment.