The senior author
of the paper and study collaborator was Dr. Robert S. Langer, ScD, FREng, who
is the David H. Koch Institute Professor at MIT. The lead authors of the paper
were Dr. Yan Pang, PhD and Dr. Jinyao Liu, PhD, who are former postdoctoral
fellows in Langer's lab at MIT.
is an endoscopic procedure used
for examining the large bowel, including the rectum and colon. Over 15 million
colonoscopies are performed annually in the US. Around 20 percent of these
involve resection of polyps, which are precancerous outgrowths from the inner
lining of the colon. Surgical removal of polyps is an effective way of halting
progression to full-blown
.
Conventionally, the
polyps are removed with the help of a lasso-like tool to snare the polyps,
before cutting. During the removal of the polyps, there is a chance of tearing
the inner lining of the colon. In order to prevent this, surgeons usually
inject saline into the submucosal space, so that it acts as a cushion and
elevates the polyps from the surface of the colon lining, making it easier for
the surgeon to excise them. However, the problem is that the saline cushion is
not stable and doesn't last long. Surgical removal typically takes 10-20
minutes, but the saline cushion lasts only a few minutes, which makes it very
difficult for the surgeon to completely excise the polyps within such as short timeframe.
In this regard, Traverso says:
"The challenge is that saline dissipates very quickly, so we don't
always have enough time to go in and intervene, and may need to reinject
saline."
In order to
circumvent this problem, attempts have been made to stabilize the saline by
mixing it with cellulose or gelatin, which act as thickening agents. However,
this highly viscous mixture is difficult to inject through the narrow needle
used in the procedure.
How were the Challenges Overcome?
The research team
at MIT overcame the challenges by developing a new material that is technically
termed as a 'shear-thinning gel'. This material is a semisolid gel under normal
conditions, but turns into a liquid upon exertion of pressure, such as when
passing through a narrow needle during injection. Again, when the pressure is
released, such as when it leaves the injection needle and enters the tissues,
it turns into a solid gel. This creates a cushion that is longer-lasting than
saline and allows the surgeons enough time to resect the polyps.
"That really makes a huge difference to the gastroenterologist who is
performing the procedure, to ensure that there's a stable area that they can
then resect using endoscopic tools," says Traverso.
How was the New Material Developed?
It is possible to
make the 'shear-thinning gels' from many different types of materials. In this
case, the MIT researchers chose two biocompatible materials, capable of forming
gels. One of these was laponite, which is a synthetic clay having viscoelastic
properties and is widely used in cosmetics. The other material was alginate,
which is a polysaccharide derived from algae. Besides being biocompatible,
these materials are amenable to modification of their flow-properties.
What are the Advantages of the New Material?
The major advantage
of the new material is that it remains stable for over an hour, allowing the
surgeons ample time to remove the polyps. The researchers tested the gel in
pigs and the results were very encouraging.
An additional
advantage is the ease of manipulation of the gel's viscosity by changing its
composition. This allows the researchers to control the length of time the gel
remains solid. Longer-lasting gels can be used for other applications, such as
narrowing the gastrointestinal (GI) tract to prevent acid reflux or help in
losing weight by making the person feel full. It could also be used for
delivering drugs into the intestine.
Concluding Remarks
The research team
found that the gel did not exhibit any harmful side-effects in the pigs and are
optimistic that they could progress to human clinical trials within a matter of
three to five years.
"This is something we think can get into patients fairly quickly,"
Traverso says.
"We're really excited
about moving it forward."
Funding Source
The study was
funded by the MIT Department of Mechanical Engineering, the Alexander von Humboldt
Foundation, the National Institutes of Health, and the Division of
Gastroenterology at Brigham and Women's Hospital.
Reference : - New material could make it easier to remove colon polyps - (http://news.mit.edu/2019/easier-remove-colon-polyps-gel-0730)
Source: Medindia
