LIVINGLIVING
Enzyme nano capsules, smart sponges and insulin patches, what's
going on? We catch up on what might replace injections and infusion
sets to deliver insulin in the future.
PATCHES, SPONGES
& NANO CAPSULES
A
n article entitled,
Glucose-Responsive
Microgels Integrated with
Enzyme Nanocapsules
for Closed-Loop Insulin
Delivery, was published by the American
Chemical Society in 2013. It was written
by Dr Zhen Gu, and others, and was
credited to the Department of Chemical
Engineering, Massachusetts Institute of
Technology (MIT).
This article referred back to another
study reproduced in Nanomagazine called
Injectable 'smart sponge' holds promise
for controlled drug delivery, featuring an
interview with Gu. That article reported
that researchers had developed a drug
delivery technique for diabetes treatment
in which a sponge-like material surrounds
an insulin core. The sponge expanded
and contracted in response to blood
sugar levels to release insulin as needed.
It was proposed that the technique could
also be used for targeted drug delivery to
cancer cells too.
Gu, lead author of a paper describing
the work (and an assistant professor in
the joint biomedical engineering program
at North Carolina State University and the
University of North Carolina at Chapel
Hill) explained the point of the research:
"We wanted to mimic the function of
healthy beta-cells, which produce insulin
and control its release in a healthy body,
but what we found also held promise for
smart drug delivery targeting cancer or
other diseases."
The matrix
At the time the researchers created
a spherical, sponge-like matrix out of
chitosan, a material found in shrimp and
crab shells. Scattered throughout this
matrix are smaller nanocapsules made
of a porous polymer that contain glucose
oxidase or catalase enzymes. The
sponge-like matrix surrounds a reservoir
that contains insulin. The entire matrix
sphere is approximately 250 micrometers
in diameter and can be injected into a
patient.
When a diabetic's blood sugar rises,
the glucose triggered a reaction that
caused the nanocapsules' enzymes
to release hydrogen ions. Those ions
bound to the molecular strands of the
chitosan sponge, giving them a positive
charge. The positively charged chitosan
strands then push away from each other,
creating larger gaps in the sponge's pores
that allow the insulin to escape into the
bloodstream. As the insulin is released,
the body's glucose levels begin to drop.
This causes the chitosan to lose its
positive charge, and the strands begin
to come back together. This shrinks the
size of the pores in the sponge, trapping
the remaining insulin. "We can also adjust
the size of the overall 'sponge' matrix as
needed, as small as 100 nanometers,"
Gu said, "and the chitosan itself can be
absorbed by the body, so there are no
long-term health effects."
In tests using diabetic laboratory
mice, the researchers found the sponge
matrix was effective at reducing blood
sugar for up to 48 hours. However,
the researchers published a separate
'smart system' for insulin delivery that
maintained normal blood sugar levels for
up to 10 days. "But we learned a lot from
the promising 'sponge' research and will
further optimize it. Meanwhile, we are
already exploring applications to combat
cancer," Gu said.
The end of injections?
As an update, and as reported in the Daily
Mail on 22 June 2015 in an article called,
The end of injections for diabetics? Smart