1:17am

Wed October 10, 2012
Shots - Health Blog

Fun With Physics: How To Make Tiny Medicine Nanoballs

Originally published on Thu October 11, 2012 7:20 am

For the past decade, scientists have been toying with the notion of encapsulating medicine in microscopic balls.

These so-called nanospheres could travel inside the body to hard-to-reach places, like the brain or the inside of a tumor. One problem researchers face is how to build these nanospheres, because you'd have to make them out of even smaller nanoparticles.

"With micro- or nanoparticles, you cannot just touch them with a finger and put them together and stick them together. You need a method to do that," says Alvaro Marin.

So Marin and his colleagues at the University of Twente in the Netherlands came up with a hands-free method to assemble nanoparticles.

They took a million or so of nanoparticles (the ones they used happened to be made of plastic) and mixed them up in a drop of water. Then they put the drop of water containing the nanoparticles on a silicon chip covered with tiny bristles.

When they did that, something curious happened: The bristles helped keep the droplet intact and retain its spherical shape. It did not collapse and wet the surface of the silicon chip.

As Marin reports in the journal PNAS, the next step was pretty easy. He waited. After a while, the water evaporated.

As the water evaporates, "the particles inside the droplet have time to rearrange and stack up in a nice, neat orderly fashion, much like oranges in a grocer's stand," says David Pine of New York University. Pine was not involved in the research.

In other words, just by waiting until the water evaporated, the nanoparticles organized themselves into a slightly lumpy ball that looks a bit like a soccer ball.

By choosing the right nanoparticles, Pine says you could make nanospheres that would release their contents in response to some external signal. They could become a new kind of drug delivery system.

At least that's the idea. Someday. Maybe.

Marin is now at the Institute of Fluid Mechanics and Aerodynamics at Bundeswehr Universitat in Munich. He is fascinated by fluids and how they move. He produced a video of the evaporating water droplet, as well as one about what happens when a water droplet freezes that won an award from the American Physical Society Division of Fluid Dynamics as part of its Gallery of Fluid Motion.

Copyright 2013 NPR. To see more, visit http://www.npr.org/.

Transcript

STEVE INSKEEP, HOST:

We come now to one of our regular sports moments, Wednesday mornings. And in a minute, we'll hear from Frank Deford about why you need to root, root, root for the home team. But first, a sporty discovery in the world of science.

RENEE MONTAGNE, HOST:

What would you do if you came across a scientific paper entitled "Building Microscopic Soccer Balls with Evaporating Colloidal Fakir Drops?"

INSKEEP: A question many of us have faced. And if you are NPR science correspondent Joe Palca, you'd want to know what the heck fakir drops are and why somebody would want to make microscopic soccer balls out of them. The answer, it turns out, has implications for human health.

JOE PALCA, BYLINE: For the past decade, scientists have been toying with the notion of encapsulating medicine in microscopic balls. These so-called nanospheres could travel inside the body to hard to reach places, like the brain or the inside of a tumor. One problem researchers face is how to build these nanospheres, because you'd have to make them out of even smaller nanoparticles.

ALVARO MARIN: With micro or nanoparticles, you cannot just touch them with a finger and put them together and stick them together. You need a method to do that, no?

PALCA: Alvaro Marin and his colleagues, at the University of Twente in the Netherlands, came up with a method to assemble nanoparticles. He took a million or so of nanoparticles - the ones he used happened to made of plastic - and mixed them up in a drop of water. Then he put the drop of water containing the nanoparticles on a silicon chip covered with tiny pillars. When he did that, something curious happened.

MARIN: The droplet stays on top of these pillars.

PALCA: And kept its nearly spherical shape. The tiny pillars kept the droplet from collapsing. It's somewhat like those guys called fakirs, sometimes called fakirs, who can lie on top of a bed of nails without sinking down to the bed. As Marin reports in the journal, PNAS, the next step was pretty easy. He waited. After a while the water evaporated.

Physicist David Pine of New York University explains what was happening as the water evaporated.

DAVID PINE: The particles inside the droplets have time to rearrange and stack up in a nice, neat orderly fashion, much like oranges in a grocer's stand.

PALCA: In other words, just by waiting until the water evaporated, the nanoparticles organized themselves into a slightly lumpy ball that looks a bit like a soccer ball. By choosing the right nanoparticles, Pine says you could make nanospheres that would release their contents in response to some external signal And your fakir droplet-produced micro soccer balls become a drug delivery system. At least that's the idea - well, someday, maybe.

Joe Palca, NPR News, Washington.

MONTAGNE: And you can watch real pictures of the water droplet shrinking into a nano soccer ball and other cool experiments from Alvaro Marin's lab at npr.org. Transcript provided by NPR, Copyright NPR.

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