Skip to Content

Shape Matters for Nanoparticles

Particles the size and shape of bacteria could more effectively deliver medicine to cells.
August 7, 2008

Nanoparticles shaped to resemble certain bacteria can more easily infiltrate human cells, according to a new study. The results suggest that altering the shape of nanoparticles can make them more effective at treating disease.

Cell invaders: Cylindrical nanoparticles slip easily into cells. They could be used to deliver drugs to cancerous tissues.

Joseph DeSimone, a professor of chemistry and chemical engineering at the University of North Carolina at Chapel Hill and at North Carolina State University, tested how nano- and microparticles shaped like cubes, squat cylinders, and long rods were taken up into human cells in culture. He found that long, rod-shaped particles slipped into cells at four times the rate of short, cylindrical shapes with similar volumes. DeSimone, who reported the findings this week in the Proceedings of the National Academy of Sciences, notes that the faster nanoparticles resemble certain types of bacteria that are good at infecting cells. “A lot of rodlike bacteria get into cells quickly,” he says. “Using the same size and shape, our particles get in very quickly too.”

Researchers have long suspected that mimicking the distinctive shapes of bacteria, fungi, blood cells–even pollen–could improve the ability of nanoparticles to deliver drugs to diseased cells in the body. But it has been difficult to test this suspicion. What’s needed is a way to quickly make billions of particles of identical size, chemistry, and shape, and then systematically vary these parameters to learn what effect they have.

DeSimone developed a way to easily design and test a wide variety of particle shapes, while at the same time controlling for size and chemical composition. For example, he can make particles of various shapes–boomerangs, donuts, hex nuts, cylinders, cubes–while keeping the size constant. He can also make boomerang-shaped particles of various sizes, or keep size and shape constant and vary only the chemical composition of the particles. The process gives researchers an unprecedented level of control, he says, which makes it easy to quickly test how changing various parameters of the nanoparticles, including shape, affect how they behave in tissues.

Multimedia

  • See how to make nanoparticles shaped like boomerangs.

“Historically, most of the work with particles has been with spherical particles because making particles of different shapes has been very challenging,” says Samir Mitragotri, a professor of chemical engineering at the University of California, Santa Barbara. DeSimone “demonstrates a very powerful technology that shows [that] particles of different shapes and materials can be prepared,” Mitragotri says. “It goes well beyond current tools.” He adds that the paper shows that “shape makes a big difference in biological response.”

DeSimone also identified the precise mechanisms by which cells take in particles of different shapes. These mechanisms determine where the particles end up inside the cell. This new data could help researchers design particles that reach particular compartments within a cell that have a known level of acidity. The researchers could then fine-tune the particles so that they break down and release their cargo only once they reach the desired compartment. That way, the particles will only release drugs inside targeted cells, leaving healthy cells unharmed.

DeSimone is using his manufacturing technique to produce nanoparticles that deliver drugs to cancer cells. He’s starting trials in mice for a number of cancer types–breast, ovarian, cervical, lung, prostate–and lymphoma. He’s able to conduct so many trials because it’s easy to add different treatment molecules to his particles. Particles developed for targeting breast cancer can easily be changed to target lung cancer, for example. During the tests, DeSimone will systematically vary doses, sizes, and so on to determine the least toxic, most effective combinations. “You can now barrage a lot of different cancers and look at what’s the most efficacious design parameters you can put in the system,” he says.

DeSimone has developed particles that resemble red blood cells in size, shape, and flexibility to help them circulate in the bloodstream without being removed by biological barriers. (He’s testing these in animals as a potential basis for artificial blood.) He is also testing long, wormlike particles that can’t easily be consumed by macrophages. “The particle has to overcome so many hurdles before it reaches its destination,” Mitragotri says. Previously, researchers have been limited to changing the size and chemistry of particles. Adding the ability to control shape provides a “big boost in overcoming these hurdles,” Mitragotri says.

Keep Reading

Most Popular

wet market selling fish
wet market selling fish

This scientist now believes covid started in Wuhan’s wet market. Here’s why.

How a veteran virologist found fresh evidence to back up the theory that covid jumped from animals to humans in a notorious Chinese market—rather than emerged from a lab leak.

light and shadow on floor
light and shadow on floor

How Facebook and Google fund global misinformation

The tech giants are paying millions of dollars to the operators of clickbait pages, bankrolling the deterioration of information ecosystems around the world.

masked travellers at Heathrow airport
masked travellers at Heathrow airport

We still don’t know enough about the omicron variant to panic

The variant has caused alarm and immediate border shutdowns—but we still don't know how it will respond to vaccines.

egasus' fortune after macron hack
egasus' fortune after macron hack

NSO was about to sell hacking tools to France. Now it’s in crisis.

French officials were close to buying controversial surveillance tool Pegasus from NSO earlier this year. Now the US has sanctioned the Israeli company, and insiders say it’s on the ropes.

Stay connected

Illustration by Rose WongIllustration by Rose Wong

Get the latest updates from
MIT Technology Review

Discover special offers, top stories, upcoming events, and more.

Thank you for submitting your email!

Explore more newsletters

It looks like something went wrong.

We’re having trouble saving your preferences. Try refreshing this page and updating them one more time. If you continue to get this message, reach out to us at customer-service@technologyreview.com with a list of newsletters you’d like to receive.