Engineers develop surgical 'duct tape' as an alternative to sutures
The sticky patch could be quickly applied to repair gut leaks and tears


Date:
February 2, 2022
Source:
Massachusetts Institute of Technology
Summary:
Engineers have developed a kind of surgical 'duct tape.' The
strong, flexible, and biocompatible sticky patch can be applied
to biological tissues and organs to help seal tears and wounds.



FULL STORY ==========================================================================
A staple on any engineer's workbench, duct tape is a quick and dependable
fix for cracks and tears in many structural materials. MIT engineers
have now developed a kind of surgical duct tape -- a strong, flexible,
and biocompatible sticky patch that can be easily and quickly applied
to biological tissues and organs to help seal tears and wounds.


==========================================================================
Like duct tape, the new patch is sticky on one side and smooth on the
other. In its current formulation, the adhesive is targeted to seal
defects in the gastrointestinal tract, which the engineers describe as
the body's own biological ductwork.

In numerous experiments, the team has shown the patch can be quickly
stuck to large tears and punctures in the colon, stomach, and intestines
of various animal models. The adhesive binds strongly to tissues within
several seconds and holds for over a month. It is also flexible, able
to expand and contract with a functioning organ as it heals. Once an
injury is fully healed, the patch gradually degrades without causing inflammation or sticking to surrounding tissues.

The team envisions the surgical sticky patch could one day be stocked in operating rooms and used as a fast and safe alternative or reinforcement
to hand-sewn sutures to repair leaks and tears in the gut and other
biological tissues.

"We think this surgical tape is a good base technology to be made into an actual, off-the-shelf product," says Hyunwoo Yuk, a research scientist
in MIT's Department of Mechanical Engineering. "Surgeons could use it
as they use duct tape in the nonsurgical world. It doesn't need any
preparation or prior step.

Just take it out, open, and use." Yuk, the study's co-lead and co-corresponding author, and his colleagues have published their
results in the journal Science Translational Medicine.Other co- authors
include MIT postdoc and lead author Jingjing Wu; project supervisor and co-corresponding author Xuanhe Zhao, who is a professor of mechanical engineering and of civil and environmental engineering at MIT; and collaborators from the Mayo Clinic and the Southern University of Science
and Technology.



==========================================================================
A gut instinct The new surgical duct tape builds on the team's 2019
design for a double-sided tape. That early iteration comprised a single
layer that was sticky on both sides and designed to join two wet surfaces together.

The adhesive was made from polyacrylic acid, an absorbent material found
in diapers, which starts out dry and absorbs moisture when in contact
with a wet surface or tissue, temporarily sticking to the tissue in the process. The researchers mixed into the material NHS esters, chemical
compounds that can bind with proteins in the tissue to form stronger
bonds. Finally, they reinforced the adhesive with gelatin or chitosan -- natural ingredients that kept the tape's shape.

The researchers found the double-sided tape strongly bonded different
tissues together. But when consulting with surgeons, they realized that
a single-sided version might make a more practical impact.

"In practical situations, it's not common to have to stick two
tissues together -- organs need to be separate from each other," Wu
says. "One suggestion was to use this sticky element to repair leaks and defects in the gut." Surgeons typically repair leaks and tears in the gastrointestinal tract with surgical sutures. But sewing the stitches
requires precision and training, and following surgery the sutures can
trigger scarring around the injury. The tissue between stitches could
also tear, causing secondary leakages that could lead to sepsis.



==========================================================================
"We thought, maybe we could turn our sticky element into a product
to repair gut leaks, similar to sealing pipes with duct tape," Wu
says. "That pushed us toward something more like single-sided tape."
Same tape, new tricks The researchers first tuned their adhesive recipe, replacing gelatin and chitosan with a longer-lasting hydrogel -- in this
case, polyvinyl alcohol.

This swap kept the adhesive physically stable for over a month, long
enough for a typical gut injury to heal. They also added a second,
nonsticky top layer to keep the patch from sticking to surrounding
tissue. This layer was made from a biodegradable polyurethane that has
about the same stretch and stiffness of natural gut tissue.

"We don't want the patch to be weaker than tissue because otherwise it
would risk bursting," Yuk says. "We also don't want it to be stiffer
because it would restrict the peristaltic movement in guts that is
essential for digestion." In initial tests, the patch did stick to
tissues, but it also swelled, just as a fully wet, hydrogel-based diaper
would. This swelling stretched the tape and the underlying tear it was
intended to seal.

"It was almost an impossible problem because hydrogel naturally swells,"
Yuk says. "But we did a simple trick: We prestretched the adhesive
layer a bit, then introduced the nonadhesive layer, so that when
applied to a tissue, that prestretching cancels out the swelling."
The team then carried out experiments to test the patch's properties
and performance. When the patch was placed in a culture with human
epithelial cells, the cells continued to grow, showing that the patch
is biocompatible.

When implanted under the skin of rats, the patch biodegraded after about
12 weeks, with no toxic effects.

The researchers also applied the patch to defects in the animals' colons
and stomachs, and found it maintained a strong bond as the injuries
fully healed.

It also produced minimal scarring and inflammation compared with repairs
made with conventional sutures.

Finally, the team applied the patch over colon defects in pigs, and
observed that the animals continued to feed normally, with no fever,
lethargy, or other adverse health effects. After four weeks, the defects
fully healed, with no sign of secondary leakage.

Taken together, the experiments suggest that the surgical patch could potentially safely repair gastrointestinal injuries, and could be
applied just as easily as commercial duct tape. Yuk and Zhao are further developing the adhesive through a new startup and hope to pursue FDA
approval to test the patch in medical settings.

"We are studying a fundamental mechanics problem, adhesion, in an
extremely challenging environment, inside the body. There are millions
of surgeries worldwide a year to repair gastrointestinal defects, and the leakage rate is up to 20 percent in high-risk patients," Zhao says. "This
tape could solve that problem, and potentially save thousands of lives."
This work was supported by the MIT Deshpande Center and the Centers for Mechanical Engineering Research and Education at MIT, and SUSTech.

========================================================================== Story Source: Materials provided by
Massachusetts_Institute_of_Technology. Original written by Jennifer
Chu. Note: Content may be edited for style and length.


========================================================================== Journal Reference:
1. Jingjing Wu, Hyunwoo Yuk, Tiffany L. Sarrafian, Chuan Fei Guo,
Leigh G.

Griffiths, Christoph S. Nabzdyk, Xuanhe Zhao. An off-the-shelf
bioadhesive patch for sutureless repair of gastrointestinal defects.

Science Translational Medicine, 2022; 14 (630) DOI: 10.1126/
scitranslmed.abh2857 ==========================================================================

Link to news story: https://www.sciencedaily.com/releases/2022/02/220202143050.htm

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