Cell culture techniques have continued to progress in order to achieve a more biomimetic environment for cell-based studies. However, oxygen concentration during cell culture is still a variable that has been largely overlooked. Conventional culturing condition is generally performed at an oxygen concentration of 20%. In comparison, cells in vivo exist at a much more hypoxic condition of 3% oxygen concentration. As more studies continue to demonstrate that oxygen concentration can affect cellular activities, monitoring local oxygen concentration as well as oxygen consumption rates by the cells will be crucial in creating a more biomimetic environment.

In the current work, an oxygen sensor, based on the quenching of a platinum fluorophore, is investigated as a technique to monitor the local oxygen concentration. The Stern-Volmer equation is used to characterize the change of fluorescent intensity due to oxygen concentration. Platinum-dye incorporated PDMS is spin-coated onto glass cover slips to produce thin film oxygen sensor. To facilitate the attachment of cells, the surface of the oxygen sensor is coated with ECM proteins. Combining with time-lapsed phase contrast microscopy, the current system allows simultaneous monitoring of local oxygen concentration and the effects on cellular morphology. Cell viability assay and other fluorescent techniques can be utilized simultaneously to provide information regarding cell viability and oxygen concentration. During normal metabolism, cells consume oxygen which subsequently alters the local oxygen concentration. This study will examine the changes of oxygen concentration during cell culture. In addition, conclusions regarding cell density and oxygen consumption rate will be presented. Finally, due to the large dynamic range observed by the current oxygen sensor, the feasibility of monitoring single cell oxygen consumption will also be discussed.