The days of having to have medical devices removed through an invasive procedure could be numbered. Researchers have produced gadgets such as gastric balloons that break down when light from a swallowable LED shines upon them.
The team say the approach could be extended to a broader range of medical equipment, as well as offering a new approach to delivering drugs to the right location at the right time.
“We have the ability to control when those devices break up through the application of light,” said Giovanni Traverso, co-author of the study from the Massachusetts Institute of Technology and a gastroenterologist at Brigham and Women’s hospital in the US.
At the heart of the approach is a hydrogel – a squishy, water-absorbing material made of polymers.
“You can imagine that if you put something really stiff and heavy and rigid inside your body, the rest of your tissues– which are quite soft by comparison– may have a negative reaction to that,” said Ritu Raman, first author of the research who is also from MIT.
However, hydrogels can be tweaked to make them stiffer or stretchier, while it is also possible to engineer them so they break down in certain environments, for example by exposure to acidity or heat.
The team said they chose to use light since it was easy to control and could be used across different environments in the body, while the wavelength could be selected so it did not harm surrounding tissues.
Writing in the journal Science Advances, Traverso and colleagues report how they applied their approach to gastric balloons – devices that aid weight loss by making a patient feel fuller. These are typically inserted into the stomach, inflated with a fluid and removed up to six months later – often with an endoscope.
Rather than filling the balloon with fluid, the team filled the porous shell with a material that rapidly inflates when wet, and sealed it with a pin made from their specially designed light-responsive hydrogel.
An hour after inserting the gastric balloons into the stomach of three pigs and checking they had inflated, the team passed an endoscope bearing an LED into each pig and shone light onto the hydrogel pin for 30 minutes.
Six hours after the balloon was inserted scans showed it had reduced to almost 70% of its original inflated size, suggesting the pin had broken down and the balloon’s contents released. By contrast, gastric balloons in three pigs that had not been exposed to an internal LED had continued to inflate.
The team found similar results could be produced by inserting an ingestible LED capsule into another three pigs. This was switched on for at least 70 minutes.
Both the LED endoscope and LED capsule contained a small magnet to guide it to a metallic piece near the pin of the gastric balloon. Traverso said the magnets could be chosen for strength so they would not stick together across bodily tissue.
While the team did not show that the gastric balloon was subsequently passed by the pigs, Traverso said it was very likely it would have been, since the constituent parts were now small enough to pass from the stomach into the intestines.
The team also made sections of a ring-shaped stent for the oesophagus out of the hydrogel, although this was not tested in live animals. After exposure to LEDs for 30 minutes, the stent became far squishier, with tests suggesting it would be able to pass into the stomach and out of the body. Traditionally such stents have to be removed by an endoscope.
Traverso said the study was a proof of concept and further work was needed – such as developing an approach that did not involve the LED attaching to the device. However the team was hopeful that the approach could eventually aid patients in a range of ways, including for controlling the release of drugs in the body.
Prof Mark Miodownik, a materials engineer at University College London who was not involved in the research, said the approach was a really good example of “animate” materials, adding that while light-degrading materials had been produced before, the new study showed a well-controlled trigger, a carefully tuned hydrogel fit for use in the body, and suggested the device and LED capsule could subsequently pass out of the body.
He said: “This [provides] a whole new set of possibilities for non-invasive surgery where you put stuff in the body and when it has done its job you send a little [LED] pill down. I think the next stage is probably to send the self-destruct [mechanism] with [the device] in the first place.”