The Neurocritic: The Incredible Growing Brain!

The Incredible Grow Your Own Brain (Barron Bob)

Using super absorbent material from disposable diapers, MIT neuroengineers Ed Boyden, Fei Chen, and Paul Tillberg went well beyond the garden variety novelty store "Grow Brain" to expand real brain slices to nearly five times their normal size.

Boyden, E., Chen, F. & Tillberg, P. / MIT / Courtesy of NIH

A slice of a mouse brain (left) was expanded by nearly five-fold in each dimension by adding a water-soaking salt. The result — shown at smaller magnification (right) for comparison — has its anatomical structures are essentially unchanged. (Nature - E. Callaway)

As covered by Ewan Callaway in Nature:

Blown-up brains reveal nanoscale details

Material used in diaper absorbant can make brain tissue bigger and enable ordinary microscopes to resolve features down to 60 nanometres.

Microscopes make living cells and tissues appear bigger. But what if we could actually make the things bigger?

It might sound like the fantasy of a scientist who has read Alice’s Adventures in Wonderland too many times, but the concept is the basis for a new method that could enable biologists to image an entire brain in exquisite molecular detail using an ordinary microscope, and to resolve features that would normally be beyond the limits of optics.

The technique, called expansion microscopy, involves physically inflating biological tissues using a material more commonly found in baby nappies (diapers).

. . .

“What we’ve been trying to do is figure out if we can make everything bigger,” Boyden told the meeting at the NIH in Bethesda, Maryland. To manage this, his team used a chemical called acrylate that has two useful properties: it can form a dense mesh that holds proteins in place, and it swells in the presence of water.

Sodium polyacrylate (via Leonard Gelfand Center, CMU)

Acrylate, a type of salt also known as waterlock, is the substance that gives nappies their sponginess. When inflated, Boyden's tissues grow about 4.5 times in each dimension.

Just add water

Before swelling, the tissue is treated with a chemical cocktail that makes it transparent, and then with the fluorescent molecules that anchor specific proteins to the acrylate, which is then infused into tissue. Just as with nappies, adding water causes the acrylate polymer to swell. After stretching, the fluorescent-tagged molecules move further away from each other; proteins that were previously too close to distinguish with a visible-light microscope come into crisp focus. In his NIH presentation, Boyden suggested that the technique can resolve molecules that had been as close as 60nm before expansion.

Most scientists thought it was cool, but there were some naysayers: “This is certainly highly ingenious, but how much practical use it will be is less clear,” notes Guy Cox, a microscopy specialist at the University of Sydney, Australia.

Others saw nothing new with the latest brain-transforming gimmick. Below, Marc Schuster displays his 2011 invention, the inflatable brain.