Stripes key to nanoparticle drug delivery

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."

Source: Massachusetts Institute of Technology

Related stories:

First atomic–scale compositional images of fuel-cell nanoparticles
(PhysOrg.com) -- In a step toward developing better fuel cells for electric cars and more, engineers at MIT and two other institutions have taken the first images of individual atoms on and near the surface of nanoparticles key to the eco-friendly energy storage devices.
Flower-shaped nanoparticles may lead to better batteries for portable electronics
Want more power and longer battery life for that cell phone, laptop, and digital music player? "Flower power" may be the solution. Chemists are reporting development of flower-shaped nanoparticles with superior electronic performance than conventional battery materials. These "nanoflowers" may power next-generation electronic devices, say the scientists in a report scheduled for the Oct. 8 issue of ACS' Nano Letters.
Scientists form alliance to develop nanotoxicology protocols
A team of materials scientists and toxicologists announced the formation of a new international research alliance to establish protocols for reproducible toxicological testing of nanomaterials in both cultured cells and animals. The International Alliance for NanoEHS Harmonization (IANH) was unveiled today at Nanotox 2008, one of the world's largest biennial nanotoxicological research meetings.
Scientists discover networks of metal nanoparticles are culprits in alloy corrosion
Oxide scales are supposed to protect alloys from extensive corrosion, but scientists at U.S. Department of Energy's Argonne National Laboratory have discovered metal nanoparticle chinks in this armor.
'Small' research at MSU leads to advances in energy, electronics
A Michigan State University researcher and his students have developed a nanomaterial that makes plastic stiffer, lighter and stronger and could result in more fuel-efficient airplanes and cars as well as more durable medical and sports equipment.
Gold, DNA Combination May Lead To Nano-Sensor
The ability to use genetic material to assemble nanoscopic particles of gold could be an important step toward creating tiny “spies” that will be able to infiltrate individual cells and report back in real time on the cell’s inner workings.
New ORNL process brings nanoparticles into focus
Scientists can study the biological impacts of engineered nanomaterials on cells within the body with greater resolution than ever because of a procedure developed by researchers at the Department of Energy's Oak Ridge National Laboratory.

MIT crafts bacteria-resistant films
Having found that whether bacteria stick to surfaces depends partly on how stiff those surfaces are, MIT engineers have created ultrathin films made of polymers that could be applied to medical devices and other surfaces to control microbe accumulation.

News discussion:

Nanotechnology news