Monitoring and Controlling Oxygen Levels in Microfluidic Devices

摘要

Mammalian cell culture has been traditionally performed in a static oxygen concentration of 21 mol %. However, oxygen level in vivo is significantly more hypoxic with an average oxygen concentration of 3 mol % to 5 mol %. In addition, many cells within the body experience dynamic oxygen levels. Such differences in oxygen tension have been shown to affect cell behavior, and controlling and monitoring oxygen level is crucial in creating biomimetic cell culture conditions. Previously, we have developed a luminescence-based oxygen sensor capable of monitoring cellular oxygen consumption rates in a multi-well plate format that is compatible with conventional cell microscopy techniques (e.g. phase contrast and fluorescence imaging). In the current study, we demonstrate successful integration of this oxygen sensor into a multi-layer microfluidic cell culture device. The oxygen sensor provides a facile method for continuous monitoring of on-chip oxygen levels. Polydimethyl-siloxane (PDMS) based microfluidic cell culture devices are permeable to oxygen, allowing physiologically relevant oxygen environments to be generated. Control channels are incorporated to enable on-chip control of dissolved oxygen tension. Finite element simulations and experimental measurements are in excellent agreement in monitoring oxygen diffusion through the PDMS to generate stable oxygen gradients and rapidly changing conditions on-chip. Further, on-chip calibration matches sensitivities measured outside of the microfludic environment. Cells will be monitored during culture in this microfluidic system under physiologically relevant oxygen environments.