Hydrogel Robots Pinpoint Drug Delivery

Researchers at Columbia University have created a squishy robot to enable targeted drug delivery.

by Michael Abrams
April 10, 2017

Whatever the illness, the pills we take use a "machine gun" tactic: shoot a drug through the entire body and it will be sure to hit its targetas well as everything else. The result is the heightening of side effects. Targeting the exact locale in need of medication would reduce side-effects and increase effectivity. The question is how.

The answer would be to take a combination of a handful of today’s vanguard technologies: hydrogels, 3D printing, and nanotechnology, and put them together to make an implantable robotic pillbox. Researchers at Columbia University’s Department of Biomedical Engineering have created just such a thing.

Hydrogels offer advantages. They can be bought commercially, they’re flexible and biocompatible, the Federal Drug Administration has approved them for use in humans, and their mechanical properties are easily tuned. “An implantable device for drug delivery seemed the obvious application,” says Prof. Sau Yin Chin, the lead researcher for the project, now at the Molecular Engineering Lab in Singapore’s Agency for Science and Technology Research.

Testing with Mice

After talking to her colleague, orthopedic surgeon Francis Lee, Chin and her fellow researchers focused on a device they could test by implanting it into mice with bone cancer. Where chemotherapy floods the entire body with drugs, creating a host of side effects, a robot that could deliver drugs at the site of a tumor would keep side-effects to a minimum.

The first challenge to creating the implant was fine-tuning the hydrogels to be rigid enough to operate mechanically, but soft enough to sit in the body without complication. Then there was the small matter of creating the right design. “Initially, all the ideas we had were linear devices,” says Chin. Linearity would keep the device simple to fabricate. But to accommodate the iron piece that would act as a gate to the drug-filled reservoirs, every concept they came up with was twice as big as it needed to be. “So then we turned to things that moved by rotation, a single gear design so the iron piece moves together with the different reservoirs."

“There were several points in the project where I had a design block, so I would look at old toys for inspiration,” says Chin. “When I came up with this, I didn’t know it was a Geneva drive.” It was only when a colleague with an interest in horology noted the similarity that she looked it up.

Automating Robots’ Layers

The newer squishy version of the technology can be made in layers using photo lithography. But the delicate layers need to be assembled by hand. To get the gear to turn, the researchers simply held a magnet up to a mouse when it was time for its medication. Though there is not yet a way to check externally if the drug has been properly administered, Chin could see the robot revolve when the magnet was applied. “The mice were nude mice,” she says. “The skin was very thin.”

Mice treated with the implant fared much better than mice given more traditional chemotherapy. They suffered fewer side effects, such as healthy tissue inflammation, and their tumors were more completely eliminated.

The device has yet to be tested in humans, but the potential applications are many. Any kind of tumor, is, of course, a potential target. But a new kind of stent could deliver drugs locally to help blood flow. The implant could someday also deliver cerebral fluid shots, “But I can’t imagine the kinds of animal trials you would have to do for that,” says Chin.

Whatever the application, once the production of the robot’s layers has been automated, they could be shipped in a solution to doctors, who would inject whatever drugs might be needed into tiny apertures. The doctor, or the patient, could then deliver the drug with a magnet as needed. Perhaps then we’ll see end of the of machine gun drug delivery in favor of the more accurate sniper.


Michael Abrams is an independent writer.