For a person with diabetes, monitoring blood glucose levels is an everyday hassle, usually involving finger pricks. An emerging alternative might be implantable devices that can automatically monitor levels and alert the patient when attention is needed, but powering these devices is tricky. A new prototype glucose monitor has been designed to power itself from that same glucose in bodily fluids.

Powering implantable devices has long been a challenge – after all, you can’t exactly take it out and pop it on the charger at night like you would your phone. Long-lasting batteries are the main method, but even if they last years surgery is often still required to replace them eventually. Other teams have experimented with wearable devices that charge implants wirelessly from outside the body, or disposable skin patches that monitor blood glucose without needing extra power.

Researchers at King Abdullah University of Science and Technology (KAUST) have now developed a new device that can essentially absorb energy from its environment in the human body. Not only does that remove the charging issue, but it means potentially-toxic materials used in batteries won’t need to be put into the body.

The new device is made entirely of biocompatible polymers, and it not only senses glucose but is powered by it. To do so, it’s made up of an n-type semiconducting polymer coupled to an enzyme called glucose oxidase. When this enzyme reacts with glucose in its surroundings, it extracts electrons from it and then shuttles them through the connected polymer. This can be used to sense glucose levels in fluids such as saliva.

This same polymer also acts as the anode in a fuel cell. When coupled with a cathode made of another polymer, the chemical energy from the glucose and oxygen is converted into electrical power to run the device.

Previous similar designs need some kind of mediator material to transport the electrons from the enzyme to the polymer, but these raise their own complications. Thankfully, the new design doesn’t need them at all.

"These mediators are often toxic and need to be immobilized onto the electrode surface, which complicates device miniaturization and shortens lifetime," says David Ohayon, first author of the study. "Our polymer seems to be able to host the enzyme in such proximity that it enables efficient electrical communication between the active center and the polymer backbone.”

The team says that this system can function at glucose concentrations you’d normally find in the human body. It was also found to be stable enough to last more than 30 days. Of course that’s not very long in terms of an implant – you wouldn’t want to have to get new ones every month. But that’s just how long the experiment ran for, so it likely lasts longer.

More research will need to be done to determine how practical the idea is. For now, this is a proof-of-concept.

"This fuel cell is the first demonstration of a completely plastic, enzyme-based electrocatalytic energy generation device operating in physiologically relevant media," says Sahika Inal, principal investigator of the study. "Glucose sensing and power generation are only two examples of the applications possible when a synthetic polymer communicates effectively with a catalytic enzyme-like glucose oxidase. Our main aim was to show the versatile chemistry and novel applications of this special water-stable, polymer class, which exhibits mixed conduction (ionic and electronic)."

The research was published in the journal Nature Materials.

Source: KAUST via Eurekalert