Home' Trinidad and Tobago Guardian : August 10th 2017 Contents A team of researchers from the Wyss Insti-
tute for Biologically Inspired Engineering and
the John A Paulson School of Engineering and
Applied Sciences (SEAS) at Harvard Universi-
ty has created a super-strong "tough adhesive"
that is biocompatible and binds to tissues with a
strength comparable to the body's own resilient
cartilage, even when they're wet.
Anyone who has ever tried to put on a Band-Aid
when their skin is damp knows that it can be frus-
trating. Wet skin isn't the only challenge for medical
adhesives---the human body is full of blood, serum,
and other fluids that complicate the repair of numer-
ous internal injuries. Many of the adhesive products
used today are toxic to cells, inflexible when they dry,
and do not bind strongly to biological tissue.
"The key feature of our material is the combina-
tion of a very strong adhesive force and the ability
to transfer and dissipate stress, which have histori-
cally not been integrated into a single adhesive," says
author Dave Mooney, PhD, who is a founding Core
Faculty member at the Wyss Institute and the Robert
P Pinkas Family Professor of Bioengineering at SEAS.
The research is reported in a recent issue of Science.
When first author Jianyu Li, PhD (former postdoc-
toral fellow at the Wyss Institute and now an assistant
professor at McGill University) started thinking about
how to improve medical adhesives, he found a solution
in an unlikely place: a slug.
The Dusky Arion (Arion subfuscus) slug, common
in Europe and parts of the United States, secretes a
special kind of mucus when threatened that glues it
in place, making it difficult for a predator to pry it off
its surface. This glue was previously determined to be
composed of a tough matrix peppered with positively
charged proteins, which inspired Li and his colleagues
to create a double-layered hydrogel consisting of an
alginate-polyacrylamide matrix supporting an ad-
hesive layer that has positively-charged polymers
protruding from its surface.
The polymers bond to biological tissues via three
mechanisms---electrostatic attraction to negatively
charged cell surfaces, covalent bonds between neigh-
bouring atoms, and physical interpenetration---mak-
ing the adhesive extremely strong.
But the matrix layer is equally important, says Li:
"Most prior material designs have focused only on
the interface between the tissue and the adhesive.
Our adhesive is able to dissipate energy through its
matrix layer, which enables it to deform much more
before it breaks."
In experimental tests, more than three times the
energy was needed to disrupt the tough adhesive's
bonding compared with other medical-grade ad-
hesives and, when it did break, what failed was the
hydrogel itself, not the bond between the adhesive
and the tissue, demonstrating an unprecedented level
of simultaneous high adhesion strength and matrix
The researchers tested their adhesive on a variety of
both dry and wet pig tissues including skin, cartilage,
heart, artery, and liver, and found that it bound to
all of them with significantly greater strength than
other medical adhesives.
The tough adhesive also maintained its stability and
bonding when implanted into rats for two weeks, or
when used to seal a hole in a pig heart that was me-
chanically inflated and deflated and then subjected
to tens of thousands of cycles of stretching.
Additionally, it caused no tissue damage or ad-
hesions to surrounding tissues when applied to a
liver hemorrhage in mice---side effects that were
observed with both super glue and a commercial
Such a high-performance material has many po-
tential applications in the medical field, either as a
patch that can be cut to desired sizes and applied to
tissue surfaces or as an injectable solution for deeper
It can also be used to attach medical devices to
their target structures, such as an actuator to support
heart function. "This family of tough adhesives has
wide-ranging applications," says co-author Adam
Celiz, PhD, who is now a lecturer at the Department
of Bioengineering, Imperial College London.
B26 body & soul
guardian.co.tt Thursday, August 10, 2017
The Dusky Arion (Arion subfuscus) slug, common in Europe and parts of the
United States, secretes a special kind of mucus when threatened that glues it in
place. This has inspired a new kind of medical adhesive.
Slug mucus inspires
new medical bio-glue
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