[Editors] MIT: Stripes key to nanoparticle drug delivery

[Elizabeth Thomson]

For Immediate Release
MONDAY, JUNE 9, 2008
Contact: Elizabeth A. Thomson, MIT News Office -- Phone: 617-258-5402  
-- Email: thomson at mit.edu

IMAGE AVAILABLE

=========================================
MIT: Stripes key to nanoparticle drug delivery
=========================================

CAMBRIDGE, Mass.--In work that could at the same time impact the  
delivery of drugs and explain a biological mystery, MIT engineers  
have created the first synthetic nanoparticles that can penetrate a  
cell without poking a hole in its protective membrane and killing it.

The key to their approach? Stripes.

The team found that gold nanoparticles coated with alternating bands  
of two different kinds of molecules can quickly pass into cells  
without harming them, while those randomly coated with the same  
materials cannot. The research was reported in a recent advance  
online publication of Nature Materials.

“We've created the first fully synthetic material that can pass  
through a cell membrane without rupturing it, and we've found that  
order on the nanometer scale is necessary to provide this property,”  
said Francesco Stellacci, an associate professor in the Department of  
Materials Science and Engineering and co-leader of the work with  
Darrell Irvine, the Eugene Bell Career Development Associate  
Professor of Tissue Engineering.

In addition to the practical applications of such nanoparticles for  
drug delivery and more-the MIT team used them to deliver fluorescent  
imaging agents to cells-the tiny spheres could help explain how some  
biological materials such as peptides are able to enter cells.

“No one understands how these biologically derived cell-penetrating  
materials work,” said Irvine. “So we could use the new particles to  
learn more about their biological counterparts. Could they be  
analogues of the biological system?”

When a cell membrane recognizes a foreign object such as a  
nanoparticle, it normally wraps around or “eats” it, encasing the  
object in a smaller bubble inside the cell that can eventually be  
excreted. Any drugs or other agents attached to the nanoparticle  
therefore never reach the main fluid section of the cell, or cytosol,  
where they could have an effect.

Such nanoparticles can also be “chaperoned” by biological molecules  
into the cytosol, but this too has drawbacks. Chaperones can work in  
some cells but not others, and carry one cargo but not another.

Hence the importance of the MIT work in developing nanoparticles that  
can directly penetrate the cell membrane, deliver their cargo to the  
cytosol, and do so without killing the cell.

Irvine compares the feat to a phenomenon kids can discover. “If you  
have a soap film and you poke it with a bubble wand, you'll pop it,”  
he said. “But if you coat the bubble wand with soap before poking the  
film, it will pass through the film without popping it because it's  
coated with the same material.” Stellacci notes that the coated  
nanoparticles have properties similar to the cell membrane-not  
identical-but the analogy is still apt.

Stellacci first reported the creation of the striped nanoparticles in  
a 2004 Nature Materials paper. At the time, “we noticed that they  
interacted with proteins in an interesting way,” he said. “Could they  
also have interesting interactions with cells?” Four years later, he  
and his colleagues report a resounding “yes.”

Stellacci and Irvine's coauthors are Ayush Verma, Oktay Uzun, Ying Hu  
and Suelin Chen of the Department of Materials Science and  
Engineering (MSE); Yuhua Hu of the Department of Chemical  
Engineering; Hee-Sun Han of the Department of Chemistry, and Nicky  
Watson of the Department of Biology.

Irvine has appointments in the Department of Biological Engineering  
and MSE, and is a member of the David H. Koch Institute for  
Integrative Cancer Research at MIT. He was recently named a Howard  
Hughes Medical Institute investigator.

The research was funded in part by the NSF, the NIH and the Packard  
Foundation.

--END--

Written by Elizabeth Thomson, MIT News Office