Artificial Muscles Release Medicine From Tiny Implants

Researchers here have designed implantable capsules perforated with microscopic holes to dispense medication, with each hole guarded by a tiny ring of artificial muscle made of soft, gel-like plastic.

Marc Madou, professor of materials science and engineering and lead investigator on the project, calls the plastic capsules "smart pills," although they are not meant to be swallowed. Instead, the capsules would be implanted beneath the skin.

"Our pill is different from other implants because it's 'smart' -- it gives only the amount of drug that the body needs," said Madou.

Beyond dispensing drugs to patients -- such as insulin to diabetics -- the artificial muscles could power tiny pumps for other micro-sized medical devices, or separate chemicals in the lab, Madou said.

He described the "smart pill" and its applications at a recent meeting of the American Chemical Society in Washington, D.C. and in a keynote address for the conference Eurosensors XIV in Copenhagen, Denmark.

The artificial muscle work builds upon Madou's previous work in microsensors and biomedical microelectromechanical devices. He has developed tiny sensors that will reside on the outside of the plastic capsules to sense concentrations of certain chemicals in a patient's bloodstream.

When sensors detect that a patient needs medication, the artificial muscles will shrink away from the holes in the wall to let medicine pass into the bloodstream. Once the right amount of medicine has left the capsule, the muscles will swell back up, and plug the holes once again.

When the capsule runs out of medicine, it could be surgically removed and a new one implanted, Madou said.

The matchstick-sized plastic capsules measure one inch long and four millimeters wide. The perforations and the artificial muscle rings that cover them measure only a few micrometers across, much smaller than the diameter of a human hair.

Madou cautioned that the capsule is in the early stages of development, and will have to work in clinical trials and achieve approval of the Food and Drug Administration before the general public will ever be able to use it. He estimates the capsule won't be commercially available for another five or 10 years.

Madou first developed the capsules while president of Teknekron Sensor Development Corporation in Menlo Park, CA, a company he founded. At the time, he built the capsules out of silicon, as one-time use devices.

Back then, he'd covered the tiny holes with curtains of thin metal that would corrode away electrochemically inside the body, releasing the capsules' contents.

After coming to Ohio State in 1997, Madou set about finding a way to open the holes and close them again.

Inspiration came from a child's toy, Madou said. A miniature sponge man -- the kind that expands in water -- gave him the idea to try artificial muscles.

Madou and his colleagues then synthesized a super-expanding polymer hydrogel that swells to several times its original size.

In their latest work, the researchers connected the hydrogel to a "backbone" of conducting plastic. When the plastic carries an electrical signal to the hydrogel, the muscles shrink, opening the holes in the capsule.

The electrical signals come from a tiny battery connected to a sensor that resides on the outside of the capsule.

When the sensor detected high levels of glucose, for instance, it would trigger the battery to charge the conducting plastic, and the holes would open to dispense insulin, Madou said.

Madou conducted this research with his previous graduate student Debbie Low, and current graduate student Harry Keqin He.

Madou has co-founded a start-up company, ChipRx, to commercialize the capsule. Ohio State, the University of Kentucky, Edison BioTechnology Center, Inc., and the Science and Technology Campus Corp. will jointly operate the company.

The Edison BioTechnology Center, part of the Ohio Department of Development's Thomas Edison Program, has offices in Cleveland, Columbus, and Cincinnati and is affiliated with the Edison Biotechnology Institute at Ohio University in Athens.

The Science and Technology Campus, located in Columbus, is a business incubator that commercializes Ohio State University technology.

Money to found ChipRx came from the Ohio Technology Action Fund, a joint program of the Governor's Office of Science and Technology and the Ohio Science and Technology Council.