[Catalyst 2016] Final

DEFECT
PATCH
THE BAND-AID FOR
THE HEART
BY SONAL PAI
I
magine hearing that your newborn,
only a few minutes out of womb, has
a heart defect and will only live a couple
more days. Shockingly, 1 in every 125
babies is born with some type of congenital
heart defect, drastically reducing
his or her lifespan. 1 However, research
institutes and hospitals nationwide are
testing solutions and advanced devices to
treat this condition. The most promising
approach is the defect patch, in which
scaffolds of tissue are engineered to
mimic a healthy heart. The heart is
enormously complex; mimicking is easier
said than done. These patches require
a tensile strength (for the heart’s pulses
and variances) that is greater than that
of the left ventricle of the human. 1 To
add to the difficulty of creating such a
device, layers of the patch have to be not
only tense and strong, but also soft and
supple, as cardiac cells prefer malleable
tissue environments.
Researchers have taken on this challenge
and, through testing various biomaterials,
have determined the compatibility of
each material within the patch. The
materials are judged on the basis of
their biocompatibility, biodegradable
nature, reabsorption, strength, and
shapeability. 2 Natural possibilities include
gelatin, chitosan, fibrin, and submucosa. 1
Though gelatin is easily biodegradable, it
has poor strength and lacks cell surface
adhesion properties. Similarly, fibrin
binds to different receptors, but with
weak compression. 3 On the artificial
“THE FUTURE FOR
DEFECT PATCHES IS
EXTREMELY PROMISING
AND EXCITING FOR THE
HEALTHCARE INDUSTRY.”
side, the polyglycolic acid (PGA) polymer,
is strong and porous, while the poly
lactic co-glycolic acid (PLGA) polymer
has regulated biological properties, but
poor cell attachment. This trade-off
between different components of a good
patch is what makes the building and
modification of these systems so difficult.
Nevertheless, the future of defect patches
is extremely promising.
An unnatural polymer that is often used
in creating patches is polycaprolactone,
or PCL. This material is covered with
gelatin-chitosan hydrogel to form a
hydrophilic (water-conducive) patch. 1 In
the process of making the patch, many
different solutions of PCL matrices are
prepared. The tension of the patch is
measured to make sure that it will not
rip or become damaged due to increased
heart rate as the child develops. The force
of the patch must always be greater than
that of the left ventricle to ensure that
the patch and the heart muscles do not
rupture. 1 Although many considerations
must be accounted for in making this
artificial patch, the malleability and
adhesive strength of the device are the
most important. 1 Imagine a 12-year-old
child with a defect patch implanted in
the heart. Suppose this child attempts
to do a cardio workout, including 100
jumping jacks, a few laps around a track,
and some pushups. The heart patch
must be able to reach the ultimate tensile
strain under stress without detaching or
bursting. The PCL core of the patch must
also be able to handle large bursts of
activity. Finally, the patch must be able to
grow with the child and the heart must
be able to grow new cells around the
21
CATALYST