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Inspired by a parasitic worm that digs its sharp teeth into its host’s intestines, Johns Hopkins researchers have designed tiny, star-shaped microdevices that can latch onto intestinal mucosa and release drugs into the body.
Image caption:When an open theragripper, left, is exposed to internal body temperatures, it closes on the instestinal wall. In the gripper’s center is a space for a small dose of a drug.
David Gracias, a professor in the Whiting School of Engineering, and gastroenterologist Florin M. Selaru, director of the Johns Hopkins Inflammatory Bowel Disease Center, led a team of researchers and biomedical engineers that designed and tested shape-changing microdevices that mimic the way the parasitic hookworm affixes itself to an organism’s intestines.
The “theragrippers” are made of metal and a thin, shape-changing film, then coated in heat-sensitive paraffin wax. The devices, each roughly the size of a dust speck, can potentially carry any drug and release it gradually into the body.
Gradual or extended release of a drug is a long-sought goal in medicine. Selaru explains that a problem with extended-release drugs is they often make their way entirely through the gastrointestinal tract before they’ve finished dispensing their medication.
“Normal constriction and relaxation of GI tract muscles make it impossible for extended-release drugs to stay in the intestine long enough for the patient to receive the full dose,” says Selaru, who has collaborated with Gracias for more than 10 years. “We’ve been working to solve this problem by designing these small drug carriers that can autonomously latch onto the intestinal mucosa and keep the drug load inside the GI tract for a desired duration of time.”
Thousands of theragrippers can be deployed in the GI tract. When the paraffin wax coating on the grippers reaches the temperature inside the body, the devices close autonomously and clamp onto the colonic wall. The closing action causes the tiny, six-pointed devices to dig into the mucosa and remain attached to the colon, where they are retained and release their medicine payloads gradually into the body. Eventually, the theragrippers lose their hold on the tissue and are cleared from the intestine via normal gastrointestinal muscular function.