Coincident with the safety audit , there’s been a bit of a discussion over at the Science Advisory Board about ethidium bromide, ‘safer’ alternatives and other ploys used by unscrupulous marketeers to get you to buy their company’s product.
Ethidium bromide (EtBr), for the non mol-biologists among us, is used to stain nucleic acid so that we can actually see it in gels . Because EtBr allegedly comes up as a mutagen when assayed using the Ames Test (and google for it yourself), it’s got quite the reputation for being one of the worst things in the mol biol lab. This is an ideal situation for the marketeers, because it means they can play on lab rats’ fears to sell over-priced, under-performing crap.
It turns out that the whole argument against EtBr is so much elephant poo anyway. Perhaps the strongest evidence for the continued use of EtBr is that it has been used for years to treat sleeping sickness in African cattle. And if you do the sums, to get the EtBr dose equivalent that is used to treat one cow, you’d need to drink fifty thousand litres of gel staining solution.
Moreover, when a company decided to test their own EtBr substitute for toxicity and mutagenicity against the ‘leading brand’, they found that yes, their alternative was safer than the competition, but there was no evidence that it was any safer than EtBr itself:
In the graph, notice how SYBR Green — the ‘leading brand’ — goes up, which is bad, and then goes down, because the test cells are dying, which is very bad. EtBr (’EB’) itself seems to be about as dangerous (i.e. not very) as EvaGreen, the company’s chemical being tested. Notice that there is no dose-response effect, which implies that any EtBr mutagenicity that is being detected is noise in the system. Indeed, I might suggest that the falling off in ‘mutagenicity’ in the three right-most EvaGreen columns is itself indicating a cytotoxic effect. Gosh.
And given that these alternatives are generally less sensitive than EtBr, which means you have to use more, EtBr begins to look like a clear winner.
Nicely put, thank you.
I recall using EtBr to stain DNA in agarose gels back in 1998-1999. There was a bright investigator in the lab who suggested that SYBR green could be used instead because this fluorochrome can be excited satisfactorily with visible blue light (additionally to Ultra Violet light, which is the only choice you have to excite EtBr). Therefore, using an array of blue LEDs, you could do without a UV trans-illuminator. But this has nothing to do with the toxicity of the dyes per se.