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Ethidium Bromide: the Classic, Carcinogenic Stain

Ethidium Bromide (EtBr) is the classic staining method for imaging gels and viewing bands of DNA. We can see our DNA because EtBr intercalates into the DNA structure and glows under UV light. However, because EtBr gets entangled in DNA, it is also a dangerous carcinogen. This poses a major threat to lab safety, because once EtBr is diluted enough to use, it is clear and untraceable if someone or something becomes contaminated with it.

There are other, less carcinogenic options for DNA staining, but EtBr is the cheapest standard for staining in biology laboratories. With the recent growth of synthetic biology across the world, it is important that everyone has access to cost-effective safety practices. To aid our fellow beginner biologists who operate under funding constraints, we designed a new safety practice technique for users of EtBr to detect contamination: coloring it with food dye.

We have demonstrated that coloring diluted EtBr with food dye not only shows where traces of EtBr have been left (an extremely useful feature even for senior lab members!) but especially for young scientists who are still learning about contamination. We believe this is a very useful approach to teaching lab safety because it provides immediate, visual feedback to users about contamination.

Perhaps the most useful and important quality about our new safety practice is that is does NOT affect the imaging of the bands under UV light. Because of the cost-efficiency, ease of use, high fidelity, and pretty gels, we have been staining our lab's gels in food-colored EtBr.