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SPECIALITY




                                             “We thought, maybe we could turn    patch to defects in the animals’
                                     7       our sticky element into a product to   colons and stomachs, and found
                                             repair gut leaks, similar to sealing   it maintained a strong bond as the
        author Jingjing Wu; project super-   pipes with duct tape,” Wu says.     injuries fully healed. It also produced
        visor and co-corresponding author    “That pushed us toward something    minimal scarring and inflammation
        Xuanhe Zhao, who is a professor of   more like single-sided tape.”       compared with repairs made with
        mechanical engineering and of civil                                      conventional sutures.
        and environmental engineering at     Same tape, new tricks
        MIT; and collaborators from the Mayo                                     Finally, the team applied the patch
        Clinic and the Southern University of   The researchers first tuned their   over colon defects in pigs, and ob-
        Science and Technology.              adhesive recipe, replacing gelatin   served that the animals continued to
                                             and chitosan with a longer-lasting   feed normally, with no fever, lethargy,
        A gut instinct                       hydrogel -- in this case, polyvinyl al-  or other adverse health effects. After
                                             cohol. This swap kept the adhesive   four weeks, the defects fully healed,
        The new surgical duct tape builds on   physically stable for over a month,   with no sign of secondary leakage.
        the team’s 2019 design for a dou-    long enough for a typical gut injury
        ble-sided tape. That early iteration   to heal. They also added a second,   Taken together, the experiments sug-
        comprised a single layer that was    nonsticky top layer to keep the     gest that the surgical patch could po-
        sticky on both sides and designed to   patch from sticking to surrounding   tentially safely repair gastrointestinal
        join two wet surfaces together.      tissue. This layer was made from    injuries, and could be applied just as
                                             a biodegradable polyurethane that   easily as commercial duct tape. Yuk
        The adhesive was made from poly-     has about the same stretch and      and Zhao are further developing the
        acrylic acid, an absorbent material   stiffness of natural gut tissue.   adhesive through a new startup and
        found in diapers, which starts out                                       hope to pursue FDA approval to test
        dry and absorbs moisture when in     “We don’t want the patch to be      the patch in medical settings.
        contact with a wet surface or tissue,   weaker than tissue because oth-
        temporarily sticking to the tissue in   erwise it would risk bursting,” Yuk   “We are studying a fundamental
        the process. The researchers mixed   says. “We also don’t want it to be   mechanics problem, adhesion, in an
        into the material NHS esters, chem-  stiffer because it would restrict the   extremely challenging environment,
        ical compounds that can bind with    peristaltic movement in guts that is   inside the body. There are millions of
        proteins in the tissue to form stronger   essential for digestion.”      surgeries worldwide a year to repair
        bonds. Finally, they reinforced the                                      gastrointestinal defects, and the
        adhesive with gelatin or chitosan    In initial tests, the patch did stick to   leakage rate is up to 20 percent in
        -- natural ingredients that kept the   tissues, but it also swelled, just as   high-risk patients,” Zhao says. “This
        tape’s shape.                        a fully wet, hydrogel-based diaper   tape could solve that problem, and
                                             would. This swelling stretched the   potentially save thousands of lives.”
        The researchers found the dou-       tape and the underlying tear it was
        ble-sided tape strongly bonded       intended to seal.                   This work was supported by the MIT
        different tissues together. But when                                     Deshpande Center and the Centers
        consulting with surgeons, they real-  “It was almost an impossible prob-  for Mechanical Engineering Re-
        ized that a single-sided version might   lem because hydrogel naturally   search and Education at MIT, and
        make a more practical impact.        swells,” Yuk says. “But we did a    SUSTech.
                                             simple trick: We prestretched the
        “In practical situations, it’s not com-  adhesive layer a bit, then introduced   Story Source:
        mon to have to stick two tissues     the nonadhesive layer, so that when   Materials provided by Massachu-
        together -- organs need to be sepa-  applied to a tissue, that prestretch-  setts Institute of Technology. Orig-
        rate from each other,” Wu says. “One   ing cancels out the swelling.”    inal written by Jennifer Chu. Note:
        suggestion was to use this sticky                                        Content may be edited for style and
        element to repair leaks and defects in   The team then carried out experi-  length.
        the gut.”                            ments to test the patch’s properties
                                             and performance. When the patch     Journal Reference:
        Surgeons typically repair leaks and   was placed in a culture with human   1. Jingjing Wu, Hyunwoo Yuk, Tif-
        tears in the gastrointestinal tract   epithelial cells, the cells continued   fany L. Sarrafian, Chuan Fei Guo,
        with surgical sutures. But sewing the   to grow, showing that the patch is   Leigh G. Griffiths, Christoph S. Nab-
        stitches requires precision and train-  biocompatible. When implanted    zdyk, Xuanhe Zhao. An off-the-shelf
        ing, and following surgery the sutures   under the skin of rats, the patch   bioadhesive patch for sutureless
        can trigger scarring around the injury.   biodegraded after about 12 weeks,   repair of gastrointestinal defects. Sci-
        The tissue between stitches could    with no toxic effects.              ence Translational Medicine, 2022;
        also tear, causing secondary leakag-                                     14 (630) DOI: 10.1126/scitranslmed.
        es that could lead to sepsis.        The researchers also applied the    abh2857



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