Remote-Controlled Biodissolving Implants Could Cure Infections

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A new kind of implant can cure bacterial infections via remote control and dissolve inside the body after a predetermined period, from just a few hours to several weeks or even months.

In a paper published today in the Proceedings of the National Academy of Sciences, researchers from Tufts University and the University of Illinois at Urbana-Champaign describe how they designed and tested an implant made of a magnesium transistor and power-receiving coil, a biodegradable circuit board, and a silk casing.

Sturdy enough to be handled in surgery, the implant neatly dissolves itself in the body.

Although led by Tufts University researchers (Hu Tao and Suk-Won Hwang are the lead authors), the team included John Rogers, a professor of engineering at the University of Illinois at Urbana-Champaign who's been at the forefront of dissolvable biosensor tech for years.

The researchers' device can be remotely activated by a near-field energy transfer between two coils, also known as near-field coupling. An oscillating electrical current is run through the primary coil, placed just above the skin, which generates an electromagnetic field. The second, receiving coil is then placed close enough to the primary to pick up most of the energy before it dissipates. It's a process similar to how wireless charging for smartphones works.

The implant's magnesium transistor heats up when powered, raising the temperature of the skin around the implant. Bacterial staph infections are often treated by warming the affected area, making the device a perfect contender for treating them. The researchers tested their devices in mice and, according to the paper, it worked.

"The inhibition zones corresponded to the areas of heat treatment," the authors wrote. "Both power (thus temperature) and duration can be controlled to enhance bacterial inhibition."

Their design has several advantages over other kinds of biodissolvable implants, the authors note. First, most implants are built on silicon substrate, which is fine, but silicon takes a long time to dissolve—from weeks to months, depending on factors like thickness and temperature inside the body.

Silk, on the other hand, can be engineered to dissolve after any desired time by accounting for its crystallinity, or, in other words, the density of its crystal structure.

Second, the ability to remotely activate the implants is a huge advantage. A biodissolvable device could be implanted after surgery and activated only if an infection occurs. If not, it'll go away on its own after a couple days, or weeks, or months. Whichever your doctor prefers.

While near-field coupling somewhat limits the range in which the device can be activated, the researchers note that more power to the primary coil can increase this distance.

Tiny implants that can dissolve on their own are attractive to doctors for one main reason: not having to perform a second surgery to remove them means less chance of infection. Which would be bad enough if the implant wasn't supposed to cure an infection in the first place.

Although many hurdles need to be overcome before high-tech biodissolvable implants are used in clinical treatments—scaling up the manufacturing process is a recurring theme—the ability to remotely control them and engineer their dissolving time are serious steps forward for biodissolvable implant tech.