Tech Briefs Magazine - April 2024 - 34

Origami-Inspired Medical Patch Seals Internal Injuries
The patch can be folded around surgical tools.
Massachusetts Institute of Technology, Cambridge, MA
M
any surgeries today are performed
via minimally invasive procedures, in
which a small incision is made, and miniature
cameras and surgical tools are threaded
through the body to remove tumors
and repair damaged tissues and organs.
The process results in less pain and shorter
recovery times compared to open surgery.
While many procedures can be performed
in this way, surgeons can face challenges
at an important step in the process:
the sealing of internal wounds and tears.
Taking inspiration from origami, MIT
engineers have now designed a medical
patch that can be folded around minimally
invasive surgical tools and delivered
through airways, intestines, and other narrow
spaces, to patch up internal injuries.
The patch resembles a foldable, paper-like
film when dry. Once it makes contact with
wet tissues or organs, it transforms into a
stretchy gel, similar to a contact lens, and
can stick to an injured site.
In contrast to existing surgical adhesives,
the team's new tape is designed to
resist contamination when exposed to
bacteria and bodily fluids. Over time,
the patch can safely biodegrade away.
The team has published its results in the
journal Advanced Materials.
The researchers are working with clinicians
and surgeons to optimize the design
for surgical use, and they envision that the
new bioadhesive could be delivered via
minimally invasive surgical tools, operated
by a surgeon either directly or remotely via
a medical robot.
" Minimally invasive surgery and robotic
surgery are being increasingly adopted, as
they decrease trauma and hasten recovery
related to open surgery. However, the sealing
of internal wounds is challenging in
these surgeries, " said Xuanhe Zhao, Professor
of Mechanical Engineering and of Civil
and Environmental Engineering at MIT.
" This patch technology spans many
fields, " added co-author Christoph Nabzdyk,
a cardiac anesthesiologist and
critical care physician at the Mayo Clinic
in Rochester, Minnesota. " This could
be used to repair a perforation from a
coloscopy, or seal solid organs or blood
vessels after a trauma or elective surgical
intervention. Instead of having to carry
out a full open surgical approach, one
could go from the inside to deliver a
34
MIT engineers have designed paper-like medical tapes that can fold around surgical tools and transform
into soft, strong adhesives when pressed against tissues. (Image: Felice Frankel)
patch to seal a wound at least temporarily
and maybe even long term. "
The bioadhesives currently used in
minimally invasive surgeries are available
mostly as biodegradable liquids and glues
that can be spread over damaged tissues.
When these glues solidify, however, they
can stiffen over the softer underlying surface,
creating an imperfect seal. Blood and
other biological fluids can also contaminate
glues, preventing successful adhesion
to the injured site. Glues can also wash
away before an injury has fully healed, and,
after application, they can also cause inflammation
and scar tissue formation.
Given the limitations of current designs,
the team aimed to engineer an
alternative that would meet three functional
requirements. It should be able to
stick to the wet surface of an injured site,
avoid binding to anything before reaching
its destination, and - once applied
to an injured site - resist bacterial contamination
and excessive inflammation.
The team's design meets all three requirements,
in the form of a three-layered
patch. The middle layer is the main
bioadhesive, made from a hydrogel material
that is embedded with compounds
called NHS esters. When in contact with
a wet surface, the adhesive absorbs any
surrounding water and becomes pliable
and stretchy, molding to a tissue's conwww.techbriefs.com
tours.
Simultaneously, the esters in the
adhesive form strong covalent bonds
with compounds on the tissue surface,
creating a tight seal between the two materials.
The design of this middle layer is
based on previous work in Zhao's group.
The team then sandwiched the adhesive
with two layers, each with a different
protective effect. The bottom layer is
made from a material coated with silicone
oil, which acts to temporarily lubricate
the adhesive, preventing it from
sticking to other surfaces as it travels
through the body. When the adhesive
reaches its destination and is pressed
lightly against an injured tissue, the silicone
oil is squeezed out, allowing the
adhesive to bind to the tissue.
The adhesive's top layer consists of an
elastomer film embedded with zwitterionic
polymers, or molecular chains made from
both positive and negative ions that act to
attract any surrounding water molecules
to the elastomer's surface. In this way, the
adhesive's outward-facing layer forms a water-based
skin, or barrier against bacteria
and other contaminants.
" In minimally invasive surgery, you
don't have the luxury of easily accessing
a site to apply an adhesive, " Yuk said.
" You really are battling a lot of random
contaminants and body fluids on your
way to your destination. "
Tech Briefs, April 2024

http://www.techbriefs.com

Tech Briefs Magazine - April 2024

Table of Contents for the Digital Edition of Tech Briefs Magazine - April 2024