How and why can some metals like copper be antibacterial?
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The process involves the release of copper ions (electrically charged particles) when microbes, transferred by touching, sneezing or vomiting, land on the copper surface. The ions prevent cell respiration, punch holes in the bacterial cell membrane or disrupt the viral coat, and destroy the DNA and RNA inside.
It is important to remember that bacteria and cells aren’t like us. Humans, and most multicellular creatures, have a layer of skin as protection. This prevents harmful chemicals from getting inside of us and doing damage.
Bacteria don’t really have skin. They have a membrane which constantly passes chemicals through it. A good analogy is that we have a mouth, a butt hole, and a lot of skin. Bacteria don’t have the skin so they are 100% mouth and butt hole everywhere.
There are things that we can touch but not put in our mouths. Since bacteria are 100% mouths, touching something is exactly the same as putting it in their mouth.
The second big thing to remember is that all living things are essentially just chemical processes. You put two molecules next to each other and things start to happen. All living things are essentially the universe’s largest Rübe Goldberg machines.
So, what happens is that when the bacteria touch the copper they, effectively, put it in their mouths and the copper atoms go in and wreak havoc on the carefully balanced chemical dancer inside the cell.
Anti-microbial surfaces of all types work by either being so slippery that bacteria can’t hold onto them or toxic to bacteria in this way.
As to how chemicals can interfere in the cell. The process of chemical reactions in a cell is similar to a lock and key. “Toxic” chemicals are usually ones that fit a lock in a cell better than the actual key. Once they fit into the lock, the real key can’t go in and the chemical chain that keeps the living cell/bacteria stops running.
The exact mechanism is unknown, but there are some theories.
One is that ~~positive~~ copper (or other metal) ~~ions~~ molecules interact with H2O2 within cells to form OH free radicals which interrupt cellular processes and cause them to lyse. Lysis is when a cell essentially self destructs and the cell membrane breaks apart spilling it’s guts out, destroying it. However, cells maintain a low concentration of H2O2, so this could only be partially responsible. ~~In water, the reaction of Cu+ with H2O would form H+ and OH-, not free radicals and (this statement was irrelevant)~~ observations of spraying cells in a mixture of liquid medium on surfaces in comparison to dry cells on surfaces showed that the dry cells died faster, which would seem to indicate that direct contact with the metal is responsible rather than free radicals in liquid medium.
The other prevailing theory is that the Cu+ ions interrupt cellular processes by bonding to cites normally occupied by iron ions (Fe+), which halts cellular functions needed for the cells to survive.
If you’re ready for a college level explainatiin, there is an oft cited paper here that you can read in its entirety. It was written in 2012, and I don’t know if there have been further developments because I’m not in college anymore and don’t have access to all the research databases to get full articles.
Don’t be intimidated to read scientific papers. When you come to terms or processes you don’t understand,look them up and keep following the rabbit hole until you do understand them, even if it’s just on Wikipedia.
Even if it takes you hours to get through even one sentence, there’s no shame in that, and it’s how you learn. I have a Master’s in Biomedical Engineering and was in a PhD program and that’s still how I read papers to this day. Wikipedia is a god send. I never would have made it through statistics without Wikipedia.
https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3067274/
Edit: typos and redundant phrases
Edit2: misremembered the difference between radicals and ions, so edited to clarify and make the response more correct.
The reason that I was told was that copper acts as a catalyst in the oxidation of fatty acids. This is the same reason that you can not use copper piping for milk. If you run milk through copper pipe it comes out rancid. That is why in many food products glass or stainless is used instead of copper.
IIRC copper as it oxidizes tends to yank all the oxygen out pf microlife that gets too close to it. Copper is basically toxic to microbes, it can be very disruptive to them. It doesn’t affect us that much because we can easily afford to lose the cells that get too close to copper and anyway, we have a protective layer of inert cells in the outer skin that prevent serious contact harm.
The best way to think about it is that copper, at a microscopic level, is a form of “spikey”. Not in a physical sense, but in a biological sense, because ions (charged bits that naturally form as electrons zip around) on the surface of the copper are able to poke holes in cells. Mind you, this is all cells, including ours, but our skin has an outer layer of dead cells that help protect the living ones so its not such a big deal. Even if it was to come in contact with living cells, it would just cause some irritation as long as its not being directly exposed to something like your nerves (in which case you have bigger issues, such as how did metallic copper get into your body in the first place).
Now, for single cell organisms, a pierced cell is pretty bad. We can shrug it off since we repopulate cells pretty rapidly, and can afford to lose a few thousand without even noticing it. But if all you have is the one cell, when it gets pierced its pretty much a death sentence.
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“All living things are essentially the universe’s
largest Rube Goldberg machines.”
Is my quotable quotes of the day. Thank you!
But if enough dead bacterias accumulate on an antimicrobial surface, can’t bacterias live on the heap of dead material under and still “dirty” the surface by their presence?
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