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  • Medicine has changed a lot in the last hundred years.

  • We have better technology to look for problems, and if we find one, we're much more likely

  • to be able to fix it.

  • And one of the most important fixes is that these days, we have antibiotics, which are

  • really good at killing off harmful bacteria.

  • Or at least, they have been, so far.

  • But the more we use those antibiotics, the more bacteria develop resistance to them,

  • so we keep having to find new ones that the bacteria haven't figured out how to fight

  • yet.

  • Which is why scientists are looking at the possibility of bringing metal back into our

  • anti-bacterial arsenal.

  • Metals like copper and silver have been used to kill bacteria for thousands of years -- even

  • before anyone knew what bacteria were.

  • For example, one of the oldest books in the world, an Egyptian medical text called the

  • Edwin Smith Papyrus, describes the use of copper for preventing infections in chest

  • wounds..

  • And many ancient cultures believed that copper and silver pots kept water safe to drink for

  • longer.

  • Then, in 1928, a guy named Alexander Fleming came along, found some funky mold in his lab,

  • and promptly changed history forever.

  • He'd discovered penicillin, the first of many antibiotics.

  • When it was released, the world went crazy for it.

  • Antibiotics were hailed asmiracle drugsand medical metals were all-but forgotten

  • about.

  • If only it were that easy, though.

  • Bacteria evolve fast, and highly resistant bacteria seem to show up almost as fast as

  • we can invent new drugs.

  • The antibiotics work a bit like an arrow, precisely hitting one weak point of the target.

  • It works great until the weak point is covered uplike when bacteria evolve antibiotic

  • resistance.

  • If today's antibiotics are like arrows, metals act more like grenades -- they hit

  • bacteria harder and in multiple places at once, making it much more difficult for them

  • to evolve resistance.

  • Back in the 1980s, researchers noted that bacteria landing on surfaces made of copper

  • -- or alloys that contain copper, like bronze and brass -- usually die off within minutes

  • or hours.

  • It's a process known as contact killing, and recently, health professionals have started

  • using it to their advantage.

  • Hospitals across the world are studying what happens when they switch out stainless steel

  • surfaces like door handles and bed rails with copper and brass.

  • One 2010 study in Birmingham, England studied the bacteria-fighting properties of copper

  • and brass.

  • They found 90-100% fewer bacteria on copper and brass surfaces than on stainless steel

  • even after six months.

  • And only the steel surfaces had MRSA, the multidrug resistant bacteria that's often

  • fatal.

  • Scientists still aren't clear on all the details when it comes to copper's contact

  • killing, but it probably has to do with electric charge.

  • Positive copper ions dissolve off the metal surface, attracted to negative charges on

  • the bacterial membrane.

  • Those ions punches holes in the membrane, letting more copper in.

  • Then, once they're loose in the cell, the metal ions can wreak all kinds of havoc.

  • Through various reactions copper ions can generate high energy hydroxyl radicals -- an

  • oxygen bonded to a hydrogen, with an unpaired electron that REALLY wants to bond with stuff.

  • They'll react with -- and damage -- pretty much any biological molecule, including DNA,

  • proteins, and carbohydrates.

  • Which makes it great at killing bacteria.

  • But even though it's so deadly, small amounts of copper -- like many other metals -- are

  • important for life.

  • Right now, for instance, copper is working inside proteins that keep your skin elastic,

  • produce the skin pigment melanin, and use oxygen to make energy.

  • Bacteria also need copper, and figuring out how they process it will be a big part of

  • understanding how best to use it against them.

  • Another metal that's turning out to be a useful weapon against bacteria is silver.

  • And unlike copper, we don't know of any useful functions for silver inside cells.

  • It can be deadly even in tiny amounts if it gets in.

  • In case you're now staring at your jewellery in horror, I should mention that silver metal

  • in that bulky form is harmless.

  • It's just too unreactive.

  • On the other hand, particles of nano silver -- just a few billionths of a meter across

  • -- might be an important part of the future of medicine.

  • Things behave very differently at that scale.

  • Their tiny size gives nanoparticles a lot more surface area, making them much more reactive.

  • Nanosilver is already being embedded into or used as a surface coating for medical implants,

  • releasing metal ions steadily over time to kill bacteria.

  • It's also being studied as an antibacterial agent in fields like dentistry, eye treatment,

  • surgery, and pharmaceuticals.

  • But don't expect to be popping copper or nanosilver /pills/ to cure infections just

  • yet -- ingesting something isn't the same as using it as a surface, and researchers

  • are still studying how these metals interact with bacteria -- and plain old cells -- in

  • the human body.

  • But it does look like those ancient Egyptians were onto something.

  • Thanks for watching this episode of SciShow, which was brought to you by our patrons on

  • Patreon.

  • If you want to help support this show, just go to patreon.com/scishow.

  • And don't forget to go to youtube.com/scishow and subscribe!

Medicine has changed a lot in the last hundred years.

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B2 中高級 美國腔

金属与细菌(Metal vs. Bacteria)

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    joey joey 發佈於 2021 年 06 月 28 日
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