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Derek Lowe The 2002 Model

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Derek Lowe, an Arkansan by birth, got his BA from Hendrix College and his PhD in organic chemistry from Duke before spending time in Germany on a Humboldt Fellowship on his post-doc. He's worked for several major pharmaceutical companies since 1989 on drug discovery projects against schizophrenia, Alzheimer's, diabetes, osteoporosis and other diseases. To contact Derek email him directly: Twitter: Dereklowe

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October 28, 2009

Nanotech Armor

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Posted by Derek

Now here's a completely weird idea: a group in Korea has encapsulated individual living yeast cells in silica. They start out by coating the cells with some charged polymers that are known to serve as a good substrate for silication, and then expose the yeast to silicic acid solution. They end up with hard-shell yeast, sort of halfway to being a bizarre sort of diatom.
The encapsulated cells behave rather differently, as no doubt would we all under such conditions. After thirty days in the cold with no nutrients, the silica-coated yeast is at least three times more viable than wild-type cells (as determined by fluorescent staining). On the other hand, when exposed to a warm nutrient broth, the silica-coated yeast does not divide, as opposed to wild-type yeast, which of course takes off like a rocket under such conditions. They're still alive, but just sitting around - which makes you wonder what signals, exactly, are interrupting mitosis.
The authors tried the same trick on E. coli bacteria, but found that the initial polymer coating step killed them off. That's disappointing, but not surprising, given that disruption of the bacterial membrane with charged species is the mode of action of several broad-spectrum antibiotics.

"Hmmm. . .so what?" might be one reaction to this work. But stop and think about it for a minute. This provides a new means to an biological/inorganic interface, a way to stich cell biology and chemical nanotechnology together. If you can layer yeast cells with silica and they survive (and are, in fact, fairly robust), you can imagine gaining more control over the process and extending it to other substances. A layer that could at least partially conduct electricity would be very interesting, as would layers with various-sized pores built into them. The surfaces could be further functionalized with all sorts of other molecules as well for more elaborate experiments. No, this could keep a lot of people busy for a long time, and I suspect it will.

Comments (15) + TrackBacks (0) | Category: Biological News


1. gyges on October 28, 2009 12:12 PM writes...

I'd want to fix them to polymer beads and use them in continuous flow brewing. Sorta like calcium alginate capture of yeast cells but more controlled.

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2. ralphbon on October 28, 2009 1:52 PM writes...

Remind me not to bite into that bread before renewing my dental insurance.

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3. Brooks on October 28, 2009 2:24 PM writes...

Minor typo: after "warm nutrient broth", you've got a <i) rather than <i>, thus hiding the key "does not divide" part of that sentence.

Is the silica a sufficiently hard shell to prevent the yeast cells from changing shape? Or is this just sort of a crust of separate pebbles? If it's a non-deformable shell, I would sort of wonder if the yeast could divide even if it was trying to.

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4. Kismet on October 28, 2009 5:50 PM writes...

How does it survive? Do the necessary nutrients diffuse through the silica shell? Doesn't sound very healthy for cells that depend on endo- or phagocytosis, does it? (i.e. all human cells?!)

@Brooks, I'm sure they tested whether it even *tried* to divide (e.g. looking whether the spindle formed).
But I am not sure if Derek is saying that the cells can't finish mitosis or if they don't even try (e.g. staying in G0 phase).

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5. Iulian on October 28, 2009 6:40 PM writes...

Hmmm... reminds me of an old idea I had: Injecting yeast into the blood stream, after a modification of some sort to stop it from dividing and to stop the immune system from atacking it. This stuff does both those things. It would have a huge market in places like Scotland or Russia... drunk all the time, pay only once. The glucose comes from the blood, the CO2 leaves through the lungs - perfect!

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6. Some Other Guy on October 28, 2009 7:32 PM writes...

Iulian, you are out of your mind.

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7. joopie on October 28, 2009 8:14 PM writes...

hot dang them there cells shore is sumpin else cordin to my fine mine!

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8. Interesting on October 28, 2009 10:15 PM writes...

Pretty different idea from a biomaterials standpoint. Traditionally people just tried to show that cells can survive and proliferate in the presence of a material. If it can only be done with mammalian cells....

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9. Dave Eaton on October 28, 2009 11:37 PM writes...

My dreams of a protective exoskeleton are one step closer to reality. Now, how to give yeast superpowers?

Very neat science.

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10. Patrick on October 29, 2009 12:08 AM writes...

Internalizing the encapsulated yeast, not in the blood but in the peritoneal cavity might have possibilities. Not so much for ethanol but for essential nutrients and vitamins.

Encapsulated pig cells are under trial for dibetes treatment.

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11. Donough on October 29, 2009 8:23 AM writes...

Another interesting application could be in biofuel production.

Current cells die when the alcohol levels in the fermenter get too high. By coating the cells with a selective layer the alcohol could be rejected and the cell lifetime could be prolonged.

In otherwords a selecticity membrane could be used to choose what nutrients and toxins a cell sees. Selective membranes of silica are relatively easy constructs (at least at macro scale).

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12. Iulian on October 29, 2009 10:27 AM writes...

Getting a constant concentration of alcohol in the blood is sometimes useful (as in keeping alcoholics from twitching under anesthesia, which I have witnessed and which was solved via IV drip).
11: If it would reject something as small as ethanol, the membrane would probably be impenetrable for glucose
But the possible applications could be huge, provided the body doesn't reject the silica shell, being a foreign body and everything.

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13. willis on October 29, 2009 3:23 PM writes...

"No, this could keep a lot of people busy for a long time, and I suspect it will."

I sense a government grant in the offing.

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14. interesting on October 30, 2009 7:17 AM writes...

This idea sounds similar to the Belcher group's work with viruses:

Pretty cool stuff.

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15. The Nano Age on June 15, 2010 5:38 PM writes...

Diamond-coated cells will be next!...

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