Several types of Lonza media contain labels stating, “protect from light,” but why is this? Can light exposure really be that harmful to the media?
The answer is yes! In fact, cell culture media contains various components that undergo a process called photooxidation, generating reactive oxygen species (ROS) that are toxic to cells. Scientists from the University of Strathclyde in Glasgow, Scotland found that violet-blue light in the region of 405 nm has antimicrobial activity, but at the same time can become cytotoxic to mammalian cells (1). This is an important finding, considering many labs still use ultraviolet radiation as means to sterilize culture surfaces.
Not only does light exposure influence cell viability, but it can also activate induce cell signaling. Scientists from the Institute of Environmental Medicine determined that a tryptophan-induced photoproduct called 6-Formylindolo [3,2-b] carbazole or FICZ, acts as a ligand to the aryl hydrocarbon receptor (AhR), a transcription factor that induces expression of CYP1A1 (2). This CYP enzyme is involved in many metabolic processes in the liver.
Furthermore, the effects of light exposure to culture media is not limited to bacterial and animal cells. Scientists have also found UV and blue wavelengths in unfiltered light inhibits growth of three different plant species (3).
What type of cell media components are facilitating this process? There are many, but I will mention only a few here (4).
Riboflavin (vitamin B2): Involved in redox processes for metabolism. Upon exposure to light, riboflavin becomes highly reactive, assisting in redox reactions that generate harmful ROS.
Folic acid (vitamin B9): Acts as a coenzyme in many metabolic reactions. Degradation of folic acid is accelerated by riboflavin in the presence of UV light.
Photoeffects can be reduced if antioxidants are added to the medium and more obviously, if the medium is protected from light as much as possible. It is important to consider these details when planning your experiments so that you do not waste time or effort and can protect your precious cells!
Written by Angela
Scientific Support Specialist, Lonza Pharma-Bioscience Solutions at Lonza
