Reactive oxygen species (ROS) research in drug discovery and drug delivery: Can the medium Be a Trojan Horse disguised as something benign?

In studying the roles of reactive oxygen species (ROS) in various biological processes, the availability of appropriate cell culture models is critical. Addition of H2O2 to cells is commonly used to simulate oxidative stress. In doing so, generation of highly reactive oxygen species (hROS) in cell culture is used as an indication of successful model creation. The validity of such a model is predicated on the assumption that hROS formation is the result of cellular biochemical processes and not from the medium. However, we observed a significant level of hROS in various culture media alone upon H2O2 addition, raising questions about the validity of such models and suggesting a "Trojan Horse" role for such media in compromising the data. Given the wide-spread use of the said method, we urge caution in analysing information gained from such models in redox mechanistic studies.