Placenta-on-a-Chip Microfluidic Model: Optimization of Perfusion Conditions

The design and development of a placenta-on-a-chip model is of great importance for various fields of cell biology, especially in studies of the molecular mechanisms of disease pathogenesis and the action of potential drugs. Currently, milling technique is most commonly used to fabricate microfluidic devices from thermoplastics. However, this technology leads to the formation of undesirable surface roughness, which promotes the formation of air bubbles and reduces the optical transparency of the polymer. In this regard, the problem of improving the technology of chip manufacturing and operation seems to be very important. We have analyzed various methods of surface modification of polycarbonate and further optimizing the circuit. It was shown that vapor polishing treatment with JINHF solution (JINHF, China) effectively removed roughness from the surface of the polycarbonate chip. The selected surface treatment method significantly reduced the roughness of the internal channels, which facilitated the filling of the chip without forming areas with stubborn air bubbles. During the optimization process, two “passive” methods for eliminating bubbles from the microfluidic system were explored, namely vertical positioning of the chip and creating air bubble traps inside the chip. These methods were compared with the “active” bubble removal by connecting an Elveflow trap (Elveflow Elvesys, France) with a vacuum pump to the chip. The method of vertical positioning of the organ-on-a-chip during cultivation proved to be more effective in removing air bubbles than built-in and external traps. The developed variant of the microfluidic device with the contour configuration that showed the best result was tested on the process of long-term cultivation of BeWo b30 and EA.hy926 cells as models of placenta-on-chip in dynamics.