Picture, if you will, a cargo rocket launching into space and docking on the International Space Station. The rocket maneuvers up to the station and latches on with an airtight seal so that supplies can be transferred. Now imagine a miniaturized version of that process happening inside your body.
Researchers today announced that they have built a robotic system capable of this kind of supply drop, and which functions entirely inside the gut. The system involves an insulin delivery robot that is surgically implanted in the abdomen, and swallowable magnetic capsules that resupply the robot with insulin.
The robot's developers, based in Italy, tested their system in three diabetic pigs. The system successfully controlled the pigs' blood glucose levels for several hours, according to results published today in the journal Science Robotics.
"Maybe it's scary to think about a docking station inside the body, but it worked," says Arianna Menciassi, an author of the paper and a professor of biomedical robotics and bioengineering at Sant'Anna School of Advanced Studies in Pisa, Italy.
In her team's system, a device the size of a flip phone is surgically implanted along the abdominal wall interfaced with the small intestine. The device delivers insulin into fluid in that space. When the implant's reservoir runs low on medication, a magnetic, insulin-filled capsule shuttles in to refill it.
Here's how the refill procedure would theoretically work in humans: The patient swallows the capsule just like a pill, and it moves through the digestive system naturally until it reaches a section of the small intestine where the implant has been placed. Using magnetic fields, the implant draws the capsule toward it, rotates it, and docks it in the correct position. The implant then punches the capsule with a retractable needle and pumps the insulin into its reservoir. The needle must also punch through a thin layer of intestinal tissue to reach the capsule.
In all, the implant contains four actuators that control the docking, needle punching, reservoir volume and aspiration, and pump. The motor responsible for docking rotates a magnet to maneuver the capsule into place. The design was inspired by industrial clamping systems and pipe-inspecting robots, the authors say.
After the insulin is delivered, the implant releases the capsule, allowing it to continue naturally through the digestive tract to be excreted from the body. The magnetic fields that control docking and release of the capsule are controlled wirelessly by an external programming device, and can be turned on or off. The implant's battery is wirelessly charged by an external device.
This kind of delivery system could prove useful to people with type 1 diabetes, especially those who must inject insulin into their bodies multiple times a day.
This kind of delivery system could prove useful to people with type 1 diabetes, especially those who must inject insulin into their bodies multiple times a day. Insulin pumps are available commercially, but these require external hardware that deliver the drug through a tube or needle that penetrates the body. Implantable insulin pumps are also available, but those devices have to be refilled by a tube that protrudes from the body, inviting bacterial infections; those systems have not proven popular.
A fully implantable system refilled by a pill would eliminate the need for protruding tubes and hardware, says Menciassi. Such a system could prove useful in delivering drugs for other diseases too, such as chemotherapy to people with ovarian, pancreatic, gastric, and colorectal cancers, the authors report.
As a next step, the authors are working on sealing the implanted device more robustly. "We observed in some pigs that [bodily] fluids are entering inside the robot," says Menciassi. Some of the leaks are likely occurring during docking when the needle comes out of the implant, she says. The leaks did not occur when the team previously tested the device in water, but the human body, she notes, is much more complex.
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Emily Waltz is a contributing editor at Spectrum covering the intersection of technology and the human body. Her favorite topics include electrical stimulation of the nervous system, wearable sensors, and tiny medical robots that dive deep into the human body. She has been writing for Spectrum since 2012, and for the Nature journals since 2005. Emily has a master's degree from Columbia University Graduate School of Journalism and an undergraduate degree from Vanderbilt University. She aims to say something true and useful in every story she writes. Contact her via @EmWaltz on Twitter or through her website.