Mechanically-controlled robotic implant prevents the formation of scar tissue

The formation of scar tissue is a hindrance to implantable treatment devices as it blocks essential drug release – this is known as the foreign body response, and is just as likely to interfere with many other types of implantable medical devices, leading to device failure within a year. Engineers at Massachusetts Institute of Technology (MIT) have developed a robotic mechanism that functions better and lasts longer than a typical drug-delivery implant.

The robotic device does not rely on drugs but works on “mechanical actuation” to prevent the formation of scar tissue, which is actually caused by the accumulation of neutrophils, or immune cells, around an implant. The device repeatedly inflates and deflates at a given time, thereby preventing fibrous capsules from forming around it.

When the MIT researchers implanted these devices in mice – the actuation was carried out every 12 hours, for five minutes at a time – they found that it took much longer for scar tissue to develop around the devices. Scar tissue did eventually form, but instead of the tangled collagen fibres that built up around static devices, collagen fibres surrounding actuated devices were more highly aligned, which the researchers believe may help drug molecules to pass through the tissue.

In further evaluations testing the effectiveness of insulin delivery and release, the researchers remodelled the device so that insulin release could be controlled by the actuator. Mice implanted with the actuated device maintained effective insulin delivery and blood glucose levels. However, in mice that did not receive actuation, delivery efficiency began to wane after only two weeks, and after eight weeks, almost no insulin was able to pass through the fibrous capsule around the device.

The researchers also created a human-sized version of the device which was successfully implanted in the abdomen of a human cadaver.

The current plan is to adapt the device to be used to deliver stem-cell-derived pancreatic cells that would sense glucose levels and secrete insulin when glucose is too high – such an implant could eliminate the need for patients to constantly measure their glucose levels and inject insulin, the researchers said.

“We’re using this type of motion to extend the lifetime and the efficacy of these implanted reservoirs that can deliver drugs like insulin,” explained Ellen Roche, the Latham Family Career Development Associate Professor of Mechanical Engineering and a member of MIT’s Institute for Medical Engineering and Science.

“You can imagine that we can apply this technology to anything that is hindered by a foreign body response or fibrous capsule, and have a long-term effect.”

Other possible applications the researchers have explored for this kind of device include delivery of immunotherapy to treat ovarian cancer, and delivering drugs to the heart to prevent heart failure in patients who have had heart attacks.

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