Coffee as a staining agent substitute in electron microscopy | Hacker News Reader

Coffee as a staining agent substitute in electron microscopy

phys.org

52 pointsPaulHoule32 comments

I don't really understand how coffee, lacking heavy metals, can effectively give contrast in the electron microscope. I can't access the paper but the available parts didn't seem to explain how this works.

Even without any heavy metal staining, you would end up seeing some structures. This approach allows looking at unstained / native tissue.

What is the coffee doing?

I'm puzzled by this. Why hasn't there been, over the last fifty years, a huge amount of research into EM staining techniques and which materials were best under which circumstances? Edison supposedly tried 3000 different materials for light bulb filaments before settling on charred cotton thread. Why hasn't something similar been done in this area?

Or perhaps it _has_ been done and that's why nearly everyone uses uranyl acetate? And perhaps coffee was tried decades ago and found to be generally inferior?

Of course it's been done, and there are lots of different stains available: https://www.agarscientific.com/general-consumables/chemicals...

Wow you know it’s a fun party when the first result needs to specify it’s _not_ radioactive

Oh I see - Uranyl Acetate is radioactive and this replaces it. Fun!

This seems like a friendly chemical too - “ The chemical properties of Osmium Tetroxide are such that use and handling of the chemical is often considered daunting. Although its volatility and toxicity certainly makes it a dangerous chemical, but when following the proper procedure and taking the necessary precautions, Osmium Tetroxide can be used to its full potential with limited risk to the user.

This is more toxic than glutaraldehyde and has a higher vapour pressure. Particular care must be taken to avoid breathing the vapour or allowing it to affect the eyes. ”

Uranyl acetate for staining is typically depleted and unless you have regulatory issues I don't think the radiation is a big concern, especially when you compare to the very serious toxicity of OsO4 (vapors can react with your eyes and blind you).

Interesting and makes sense! I know nothing but what I read from the stain description haha. OsO4 seems incredibly nasty. So do a few other of the stains!

You just know how they found out about this...

> "I got the idea of using espresso as a staining agent from the circular dried stains in used coffee cups,"

Suuure...

Quoting more:

> "I got the idea of using espresso as a staining agent from the circular dried stains in used coffee cups," says Claudia Mayrhofer, who is responsible for ultramicrotomy at the institute. During preparation, she cuts tissue samples into wafer-thin slices and fixes them onto sample holders. Staining is the last step before examination under the electron microscope.

I'm curious about the grad student who is the second author on the research paper. Is he the one tasked with the current-SOP staining with (radioactive and poisonous) uranyl acetate? Was it his overworked-and-drowsy "oopsie" which lead to the discovery?

Amusing, but no (at least I sincerely hope). Food and wet samples are never in the same vicinity as a matter of OSHA (plus just a general desire not to get yourself or others killed). Violating that would typically be a great way to speedrun getting fired.

Radioactive substances go beyond that, generally being handled in their own dedicated area that no one else is permitted to enter for any reason. The level of paranoia is actually fairly impressive (but obviously necessary).

I hope the staining agent is at least visually very different from Espresso.

https://en.wikipedia.org/wiki/Uranyl_acetate

- so easily distinguished from espresso. OTOH...

https://www.google.com/search?q=far+side+comic+culture+of+am...

Funny, on that page it also lists oolong tea as a staining agent.

So, coffee, tea and Uranyl acetate...

You figure they accidentally spilled some coffee and just went with it? That's my guess.

One of the references: “Oolong tea extract as a substitute for uranyl acetate in staining of ultrathin sections”

I'm reminded of how blacksmiths use instant coffee to stain damascus steel, at least the ones on YouTube

Does that last long? Commercial damascus is typically acid etched which seems like it would last better, but it wears off eventually too.

[edit] oh, I guess coffee is acidic, so maybe it’s not that different. I was thinking of using it as a stain at first

Calling it now: this is ignobel prize-worthy research. If it doesn’t get a nod I’ll eat my hat.

Make sure to leave out the hazelnut syrup.

One does not simply ... ordinary espresso.

Next up: "Coffee in Austria recalled due to high concentrations of heavy metals"

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