Microbots Use Magnetism to Send Nanoparticles to Tumors

Researchers at MIT have used magnetism as a new transport method for tiny robots that can send nanoparticles to diseased areas within the body for targeted treatment.

Researchers are finding nanotechnology particularly useful in medicine, where they are creating tiny devices that can enter the human body and perform tasks that previously were invasive or less effective than they could be.

One of these is targeted drug delivery to places in the body—such as cancerous tumors—that need healing. This is the area of focus for new research from MIT, where engineers have designed tiny robots that can help drug-delivery nanoparticles push their way directly into a tumor or another disease site, they said.

Engineers at MIT have designed a magnetic microrobot that can help push drug-delivery particles into tumor tissue (left). They also employed swarms of naturally magnetic bacteria to achieve the same effect (right). (Image source: MIT)

Exiting at the Right Place

One of the biggest challenges researchers have faced in delivering drugs using nanoparticles has been to get the particles to exit blood vessels and assemble in the right place to perform their appointed tasks. The magnetic microrobots developed by the MIT team—which were inspired by bacterial propulsion—could help researchers overcome this challenge, they said.

“Delivering drugs with nanoparticles is limited by diffusion of these particles into diseased tissue, which is hindered by physiological barriers,” Simone Schurle, a former MIT postdoc who is now a professor in the Department of Health Science and Biology at ETH Zurich, told Design News. “As a mechanical engineer, I was intrigued to think about ways that we could power the transport of drugs … ways to add energy externally to help nanoparticles move into the targeted site. “

In most previous research that uses nanoparticles to target disease sites in the body, researchers try to find sites surrounded by “leaky” blood vessels, such as tumors, which makes it easier to send the particles into the tissue.

Using Magnetism

Schurle took a different approach. She used magnetism, which she said is an ideal way to supply energy noninvasively, and she developed tiny magnetic robots while still a graduate student at Brad Nelson’s Multiscale Robotics Lab at ETH Zurich that could “push around surrounding fluid to also push nanoparticles into tissue, she said.

In 2014, she came to MIT to the lab of Sangeeta Bhatia, professor of health sciences and technology and electrical engineering and computer science, with these robots to further advance their development to move the fluid in larger volumes, Schurle said.

The robots themselves—which researchers call “artificial bacterial flagellum”—are 35 hundredths of a millimeter long, similar in size to a single cell. They are comprised of a tiny helix that resembles the flagella that many bacteria use to propel themselves, and researchers control them by applying an external magnetic field. The robots are fabricated using a high-resolution 3D printer, after which they are coated with nickel, making them magnetic. The team published a paper on its work in the journal Science Advances.

Testing the Robots

To test a single robot’s ability to control nearby nanoparticles, the researchers created a microfluidic system that mimics the blood vessels that surround tumors. They lined the channel in their system, which is between 50 and 200 microns wide, with a gel that has holes to simulate the broken blood vessels seen near tumors.

Researchers tested two different types of magnetically powered strategies to introduce local fluidic forces that enhance transport of nanoparticles into diseased tissue, Schurle explained.

“The first uses an artificial corkscrew-shaped swimmer that is spun by a rotating magnetic field to push nanoparticles with its wake toward the edges of blood vessels and into tissue,” she said. “The second approach takes a dense swarm of naturally magnetic bacteria, and overrides their natural motion using a rotating magnetic field, causing them to twirl and move together, pushing surrounding fluid in controlled directions.”

Researchers used a combination of computer modeling and experiments in a model blood vessel to better understand the details and specifics of how the robots work, testing various strategies and measuring how they influenced the accumulation of 200-nanometer fluorescent “dummy” nanoparticles outside the artificial vessel, she added.

Schurle and her collaborator Bhatia plan to continue to explore and advance both approaches to the robotic delivery system so they eventually can be tested in animal models on their way to real-life patient scenarios, she said.

Elizabeth Montalbano is a freelance writer who has written about technology and culture for more than 20 years. She has lived and worked as a professional journalist in Phoenix, San Francisco and New York City. In her free time she enjoys surfing, traveling, music, yoga and cooking. She currently resides in a village on the southwest coast of Portugal.

 

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