A gel cushion used to elevate polyps during endoscopy could reduce the risk of tearing the lining of the colon

To reduce the risk of tearing the colon during this procedure, doctors often inject saline solution into the space below the lesion, forming a "cushion" that lifts the polyp and facilitates its removal in all security. However, this cushion does not last long.

MIT researchers have developed an alternative: a solution that can be injected as a liquid but turns into a solid gel once it reaches the fabric, creating a more stable and lasting cushion.

"It makes a huge difference for the gastroenterologist who performs the procedure, to make sure that there is a stable area that he can then resect with the help of the tools endoscopic, "said Giovanni Traverso, badistant professor in the department of mechanical engineering at MIT and gastroenterologist at Brigham and Women's Hospital.

Traverso is the lead author of the study, which appears in the July 30 issue of Advanced Science. The main authors of the study are Yan Pang and Jinyao Liu, former MIT postdocs. Other authors include Zaina Moussa, MIT student, Joy Collins, technical badistant, Shane McDonnell, former technician, Alison Hayward, veterinarian, Division of Comparative Medicine, and Robert Langer, Brigham and Women's gastroenterologist Hospital.

A stable cushion

Although many colon polyps are harmless, some can become cancerous if they are not removed. Gastroenterologists often perform this procedure during a routine colonoscopy, using a lbado-like tool to hold the tissue before cutting it.

This procedure can tear the lining of the colon, which is why doctors usually inject saline into the area just below the mucosa, called the submucosal space, to lift the polyp from the colon surface.

"It allows you to separate the layers of tissue briefly and give the surface a little elevated, which makes it easier to monitor the lesion," says Traverso. "The problem is that the saline solution dissipates very quickly, so we do not always have time to enter and intervene and that it is possible -be necessary to reinject saline solution. "

Complex lesions may require 10 to 20 minutes or more, but the saline cushion lasts only a few minutes. The researchers have tried to extend the life of the cushions by adding thickeners such as gelatin and cellulose, but it is very difficult to inject them with the narrow needle used for the procedure.

To overcome this problem, the MIT team decided to create a shear thinning gel. These materials are semi-solid gels under normal conditions, but when the force is applied to them, their viscosity decreases and they flow more easily. This means that the material can be easily injected through a narrow needle and then become a solid gel once it enters the colon tissue.

Slimming gels can be made from many types of materials. To this end, researchers have opted for a combination of two biocompatible materials that can form gels – Laponite, a powdered clay used in cosmetics and other products, and Alginate, a polysaccharide derived from algae.

"We chose these materials because they are biocompatible and allow us to adapt the fluid behavior of the resulting gels," says Pang.

With the help of these materials, the researchers created a shear dilution gel that could be injected and form a stable cushion for over an hour in pork. This would give gastroenterologists much more time to eliminate polyps.

"If not, you inject the saline solution, then you change tools and when you are ready, the tissue is flat again." It becomes really difficult to resect things safely, "says Traverso.

Viscosity control

By varying the composition of the gel components, researchers can control characteristics such as viscosity, which affects the stability of the cushion. If it's designed to last longer, this type of injectable gel could be useful for applications such as narrowing the gastrointestinal tract, which could be used to prevent acid reflux or to help with weight loss. by making patients feel full. It could also be used to administer drugs to the intestinal tract, says Traverso.

The researchers also found that the material had no harmful side effects in pigs and they hoped to start testing on human patients within three to five years.

"It's something we think we can reach patients fairly quickly," says Traverso. "We are really excited to go forward."

The research was funded by the National Institutes of Health, the Alexander von Humboldt Foundation, the Brigham and Women's Hospital Gastroenterology Division and the MIT Department of Mechanical Engineering.