Ask any dentist and they will tell you that coffee stains teeth. I appreciate their concern, but they’re really barking up the wrong tree. They are right though, coffee is very effective at staining almost anything that is not brown. This is apparently true at the cellular level, even at a smaller level, as a modern study has shown that espresso effectively stains biological samples, providing improved clarity and contrast in electron microscopy.
As reported PsyPoststudy published in the journal investigated the effectiveness of espresso as a non-toxic and cost-effective way to prepare samples for electron microscopy.
Electron microscopy is the process by which biologists study the inner workings and structures of a cell at the nano level. To do this, they apply transmission electron microscopes (TEM), which apply accelerated electrons to determine the shape of the cell. The problem is that most of these cells are composed of “lightweight chemical elements such as carbon, hydrogen, oxygen and nitrogen” that do not interact strongly with electrons, thus creating a very lackluster image.
The established way to augment resolution is to “positively stain” samples, during which they are exposed to massive metals. Bulky metal ions bind to cellular structures, making them much more reflective of electrons. This creates more detailed images of the cell structure with greater contrast.
Currently, researchers apply a uranium derivative salt called uranyl acetate for positive staining. But as you might expect, it’s not perfect. PsyPost notes that it is “highly toxic to the kidneys and chemically radioactive” and requires “strict safety protocols, costly waste disposal and complicated regulatory paperwork.” Some laboratories have even banned the apply of uranyl acetate.
Enter coffee, the eco-friendly solution to all your problems. The researchers collected samples of zebrafish cells specifically selected for their complicated, double-walled mitochondrial membranes. Uranyl acetate, Robusta espresso, and chlorogenic acid (a substance found in vast amounts in espresso that the researchers hypothesized was responsible for the color) and introduced them into separate samples of zebrafish.
Each of them was examined using TEM to determine the clarity of the image formed; the clearer the lines of the membrane, the better. The images were then mathematically analyzed to measure pixel intensity, particularly in comparison to the surrounding cellular region.
They found that espresso not only produced clear, well-defined images of the membrane, but “in some cases even better than uranyl acetate,” says one of the study’s authors.
Espresso is therefore not only an ecological alternative, but a real competitor to established methods. One that is safer and cheaper. The researchers note that different biological tissues react differently due to their chemical composition – “a dye that works well on the lipids of the mitochondrial membrane may not bind equally well to a protein in a muscle fiber or DNA strand.” More research will need to be done on the effectiveness of espresso on other cell types.
So the next time you go to the dentist and they tell you you have coffee stains, you say, “You’re damn right and you’re welcome.”
