@article {Li2020.12.16.423117, author = {Chao Li and Mouhita Humayun and Keon Young Park and Bryce Connors and Jun Feng and Jiayi Li and Yanbo Feng and Ryan L. Clark and Hunter Hefti and Jonathan Schrope and Ophelia S. Venturelli and David J. Beebe}, title = {Under-oil autonomously regulated oxygen microenvironments for cell culture}, elocation-id = {2020.12.16.423117}, year = {2020}, doi = {10.1101/2020.12.16.423117}, publisher = {Cold Spring Harbor Laboratory}, abstract = {Oxygen levels in vivo are autonomously regulated by a supply-demand balance, which can be altered in disease states. However, the oxygen levels of in vitro cell culture systems, particularly microfluidic cell culture, are typically unidirectionally defined by either supply or demand. Further, the oxygen microenvironment in these systems are rarely monitored or reported. Here, we present a method to establish and dynamically monitor autonomously regulated oxygen microenvironments (AROM) using an oil overlay in an open microfluidic cell culture system. Using this method, the oxygen microenvironment is dynamically defined by both supply and demand of the system. We explore the physical laws governing kinetics of the under-oil oxygen microenvironment and experimentally validate the method using a variety of cell types including mammalian, fungal and bacterial cells. Finally, we demonstrate the utility of this method to establish a co-culture between primary intestinal epithelial cells and human-associated intestinal anaerobic bacteria.Competing Interest StatementD.J.B. holds equity in BellBrook Labs LLC, Tasso Inc., Stacks to the Future LLC, Lynx Biosciences LLC, Onexio Biosystems LLC, Turba LLC, and Salus Discovery LLC. D.J.B. is a consultant for Abbott Laboratories.}, URL = {https://www.biorxiv.org/content/early/2020/12/16/2020.12.16.423117}, eprint = {https://www.biorxiv.org/content/early/2020/12/16/2020.12.16.423117.full.pdf}, journal = {bioRxiv} }