Researchers develop tiny pacemaker that’s injectable and bioabsorbable

Engineers at Northwestern University have developed a pacemaker that can fit inside the tip of a syringe for easier implantation.

The researchers say the device could be noninvasively injected into the body. Though it can work with hearts of all sizes, they say it’s particularly well suited for the small, fragile hearts of newborn babies with congenital heart defects.

In a post on the Northwestern website, the researchers say the pacemaker is smaller than a single grain of rice. It pairs with a small, soft, flexible, wireless wearable device that mounts onto the patient’s chest to control pacing. When the wearable detects an irregular heartbeat, it automatically shines a light pulse to activate the pacemaker. These short pulses penetrate through the skin, breastbone and muscles to control the pacing.

The researchers designed the technology for temporary pacing, dissolving once it’s no longer needed. All components in the device are biocompatible, so they’re naturally absorbed into the body’s biofluids and avoid the need for surgical extraction.

Researchers published their findings in Nature. They demonstrated device efficacy across a series of large and small animal models, plus human hearts from deceased organ donors.

John Rogers, who led the development, says the team believes it’s the world’s smallest pacemaker.

“There’s a crucial need for temporary pacemakers in the context of pediatric heart surgeries, and that’s a use case where size miniaturization is incredibly important. In terms of the device load on the body — the smaller, the better,” Rogers said.

More about the pacemaker makeup

Originally, the team developed a dissolvable pacemaker about the size of a quarter. However, after it worked well in pre-clinical animal studies, cardiac surgeons asked if researchers could make the device smaller. At the time, the device was powered by near-field communication protocols, which required a built-in antenna.

Rogers said that antenna limited the ability to miniaturize it. That led the team to develop the light-based scheme. Additionally, the researchers switched power sources, using the action of a galvanic cell. This simple battery transforms chemical energy into electrical energy. So, the pacemaker uses two different metals as electrodes to deliver electrical pulses to the heart. When in contact with surrounding biofluids, the electrodes form a battery, with the resulting chemical reactions causing the electrical current to flow and stimulate the heart.

For light, the team used an infrared wavelength that safely and deeply penetrates into the body. The wearable device detects heart rate and, when it drops below a certain threshold, activates a light-emitting diode. The light then flashes on and off at a rate that corresponds to the normal heart rate.

Even though the pacemaker is so small (1.8 mm wide, 3.5 mm long and 1 mm thick), it still provides as much stimulation as a full-sized pacemaker. Additionally, because of the small size, physicians could distribute collections of them across the heart. Using multiple pacemakers in this manner could enable more sophisticated synchronization. That could pace different areas of the heart at different rhythms to, for example, terminate arrhythmias.

The researchers could look to use the technology in other bioelectronic medicines. They noted nerve and bone healing, wound treating and pain blocking.

“Because it’s so small, this pacemaker can be integrated with almost any kind of implantable device,” Rogers said. “We also demonstrated integration of collections of these devices across the frameworks that serve as transcatheter aortic valve replacements. Here, the tiny pacemakers can be activated as necessary to address complications that can occur during a patient’s recovery process. So that’s just one example of how we can enhance traditional implants by providing more functional stimulation.”

Learn more in the video below: