MIT engineers design origami-inspired medical patches for minimally invasive tissue sealing

Many surgeries today are minimally invasive surgery that involves making a small incision, passing a miniature camera and surgical instruments through the body to remove the tumor, and repairing damaged tissue or organs. This process causes less pain and shorter recovery time compared to open surgery.

Although many steps can be performed this way, surgeons can face challenges in the closure of internal wounds and lacerations, which are important steps in the process.

Inspired by origami, MIT engineers designed medical patches that could be folded around minimally invasive surgical instruments and sent to the airways, intestines, and other tight spaces to repair internal injuries. A patch resembles a paper-like film that folds when it dries. Upon contact with wet wipes or organs, it turns into a stretchy gel, such as a contact lens, which can adhere to the injured area.

In contrast to existing surgical adhesives, the team’s new tapes are designed to withstand contamination when exposed to bacteria and body fluids. Over time, the patch will safely biodegrade.The team published the results in the journal Advanced material..

Researchers are working with clinicians and surgeons to optimize surgical designs, and new bioadhesives can be delivered via minimally invasive surgical instruments that surgeons control directly or remotely via medical robots. I think.

Minimally invasive surgery and robotic surgery are increasingly being adopted to reduce trauma and accelerate the recovery associated with open surgery. However, it is difficult to block the internal injury with these surgeries. “

Xuanhe Zhao, Professor of Mechanical Engineering and Civil and Environmental Engineering at MIT

“This patch technology spans many disciplines,” adds Christoph Nabzdik, a cardiologist and emergency physician at the Mayo Clinic in Rochester, Minnesota. “It can be used to repair perforations from colonoscopy or to seal solid organs or blood vessels after trauma or selective surgical intervention. Instead of performing a fully open surgical approach. You can go from the inside to provide the patch, at least temporarily, and perhaps even in the long run, to seal the wound. “

Co-authors of this study include lead authors Sarah Wu and Hyunwoo Yuk, and MIT’s Jingjing Wu.

Hierarchical protection

The bioadhesives currently used in minimally invasive surgery are primarily available as biodegradable liquids and adhesives that can spread to damaged tissue. However, when these adhesives solidify, they can harden on the underlying soft surface, creating an incomplete seal. Blood and other body fluids can also contaminate the adhesive and prevent it from successfully adhering to the damaged area. The adhesive may be washed away before the injury is completely healed and may cause inflammation and the formation of scar tissue after application.

Given the current design limitations, the team sought to design alternatives that meet three functional requirements. It should be able to resist bacterial contamination and excessive inflammation when applied to the injured area, avoiding adhering to the wet surface of the injured area and binding to anything before reaching the destination.

The team design meets all three requirements in the form of a three-layer patch. The intermediate layer is the main bioadhesive made from a hydrogel material in which a compound called NHS ester is embedded. Upon contact with a wet surface, the adhesive absorbs the surrounding water, is flexible and stretchy, and is shaped to the contours of the tissue. At the same time, the ester of the adhesive forms a strong covalent bond with the compound on the tissue surface, creating a tight seal between the two materials. The design of this middle layer is based on Zhao’s group’s previous work.

The team then sandwiched the adhesive between two layers, each showing different protective effects. The bottom layer is made of a material coated with silicone oil, which acts to temporarily lubricate the adhesive and prevent it from adhering to other surfaces as it passes through the body. When the glue reaches its destination and is lightly pressed against the damaged tissue, the silicone oil is squeezed out, allowing the glue to bond to the tissue.

The top layer of adhesive consists of an elastomeric film with zwitterionic polymers embedded in it, or a molecular chain made up of both positive and negative ions that act to attract surrounding water molecules to the surface of the elastomer. I will. In this way, the outward layer of adhesive forms a barrier against water-based skin or bacteria and other contaminants.

“With minimally invasive surgery, you don’t have the luxury of having easy access to the site to apply the glue,” says Yuk. “You are really fighting a lot of random pollutants and body fluids on your way to your destination.”

Fits robots

In a series of demonstrations, researchers have shown that the new bioadhesive adheres strongly to animal tissue samples, even after being submerged in a liquid beaker containing blood for extended periods of time.

They also used origami-inspired techniques to fold the adhesive around instruments commonly used in minimally invasive surgery, such as balloon catheters and surgical staplers. They passed these tools through animal models of major airways and blood vessels such as the trachea, esophagus, aorta, and intestines. The patch can be applied to torn tissue or organs by inflating the balloon catheter or applying light pressure to the stapler, at or near the patched area until one month after the patch is applied. There were no signs of contamination.

Researchers believe that the new bioadhesives can be manufactured in pre-folded configurations that allow surgeons to easily fit minimally invasive instruments and tools currently used in robotic surgery. They are working with designers to integrate bioadhesives into robotic surgery platforms.

“We believe that the conceptual novelty in the shape and function of this patch represents an exciting step towards overcoming translational barriers in robotic surgery and facilitating the broader clinical adoption of bioadhesives.” Wu says.